1
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Lang X, Shi L, Zhao Z, Min W. Probing the structure of water in individual living cells. Nat Commun 2024; 15:5271. [PMID: 38902250 PMCID: PMC11190263 DOI: 10.1038/s41467-024-49404-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 06/04/2024] [Indexed: 06/22/2024] Open
Abstract
Water regulates or even governs a wide range of biological processes. Despite its fundamental importance, surprisingly little is known about the structure of intracellular water. Herein we employ a Raman micro-spectroscopy technique to uncover the composition, abundance and vibrational spectra of intracellular water in individual living cells. In three different cell types, we show a small but consistent population (~3%) of non-bulk-like water. It exhibits a weakened hydrogen-bonded network and a more disordered tetrahedral structure. We attribute this population to biointerfacial water located in the vicinity of biomolecules. Moreover, our whole-cell modeling suggests that all soluble (globular) proteins inside cells are surrounded by, on average, one full molecular layer (about 2.6 Angstrom) of biointerfacial water. Furthermore, relative invariance of biointerfacial water is observed among different single cells. Overall, our study not only opens up experimental possibilities of interrogating water structure in vivo but also provides insights into water in life.
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Affiliation(s)
- Xiaoqi Lang
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Lixue Shi
- Shanghai Xuhui Central Hospital, Zhongshan-Xuhui Hospital, and Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism, Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Zhilun Zhao
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
| | - Wei Min
- Department of Chemistry, Columbia University, New York, NY, 10027, USA.
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2
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Huang Z, Bai Y, Zhao Y, Liu L, Zhao X, Wu J, Watanabe K, Taniguchi T, Yang W, Shi D, Xu Y, Zhang T, Zhang Q, Tan PH, Sun Z, Meng S, Wang Y, Du L, Zhang G. Observation of phonon Stark effect. Nat Commun 2024; 15:4586. [PMID: 38811589 PMCID: PMC11137145 DOI: 10.1038/s41467-024-48992-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 05/15/2024] [Indexed: 05/31/2024] Open
Abstract
Stark effect, the electric-field analogue of magnetic Zeeman effect, is one of the celebrated phenomena in modern physics and appealing for emergent applications in electronics, optoelectronics, as well as quantum technologies. While in condensed matter it has prospered only for excitons, whether other collective excitations can display Stark effect remains elusive. Here, we report the observation of phonon Stark effect in a two-dimensional quantum system of bilayer 2H-MoS2. The longitudinal acoustic phonon red-shifts linearly with applied electric fields and can be tuned over ~1 THz, evidencing giant Stark effect of phonons. Together with many-body ab initio calculations, we uncover that the observed phonon Stark effect originates fundamentally from the strong coupling between phonons and interlayer excitons (IXs). In addition, IX-mediated electro-phonon intensity modulation up to ~1200% is discovered for infrared-active phonon A2u. Our results unveil the exotic phonon Stark effect and effective phonon engineering by IX-mediated mechanism, promising for a plethora of exciting many-body physics and potential technological innovations.
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Affiliation(s)
- Zhiheng Huang
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Yunfei Bai
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Yanchong Zhao
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Le Liu
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Xuan Zhao
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Jiangbin Wu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Wei Yang
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Dongxia Shi
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Yang Xu
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Tiantian Zhang
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Qingming Zhang
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Science and Technology, Lanzhou University, Lanzhou, 730000, China
| | - Ping-Heng Tan
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Zhipei Sun
- QTF Centre of Excellence, Department of Electronics and Nanoengineering, Aalto University, Tietotie 3, FI-02150, Espoo, Finland
| | - Sheng Meng
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong Province, 523808, China
| | - Yaxian Wang
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
| | - Luojun Du
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China.
| | - Guangyu Zhang
- Beijing National Laboratory for Condensed Matter Physics; Key Laboratory for Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong Province, 523808, China.
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3
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Cruz R, Ataka K, Heberle J, Kozuch J. Evaluating aliphatic CF, CF2, and CF3 groups as vibrational Stark effect reporters. J Chem Phys 2024; 160:204308. [PMID: 38814010 DOI: 10.1063/5.0198303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 05/09/2024] [Indexed: 05/31/2024] Open
Abstract
Given the extensive use of fluorination in molecular design, it is imperative to understand the solvation properties of fluorinated compounds and the impact of the C-F bond on electrostatic interactions. Vibrational spectroscopy can provide direct insights into these interactions by using the C-F bond stretching [v(C-F)] as an electric field probe through the vibrational Stark effect (VSE). In this work, we explore the VSE of the three basic patterns of aliphatic fluorination, i.e., mono-, di-, and trifluorination in CF, CF2, and CF3 groups, respectively, and compare their response to the well-studied aromatic v(C-F). Magnitudes (i.e., Stark tuning rates) and orientations of the difference dipole vectors of the v(C-F)-containing normal modes were determined using density functional theory and a molecular dynamics (MD)-assisted solvatochromic analysis of model compounds in solvents of varying polarity. We obtain Stark tuning rates of 0.2-0.8 cm-1/(MV/cm), with smallest and largest electric field sensitivities for CFaliphatic and CF3,aliphatic, respectively. While average electric fields of solvation were oriented along the main symmetry axis of the CFn, and thus along its static dipole, the Stark tuning rate vectors were tilted by up to 87° potentially enabling to map electrostatics in multiple dimensions. We discuss the influence of conformational heterogeneity on spectral shifts and point out the importance of multipolar and/or polarizable MD force fields to describe the electrostatics of fluorinated molecules. The implications of this work are of direct relevance for studies of fluorinated molecules as found in pharmaceuticals, fluorinated peptides, and proteins.
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Affiliation(s)
- R Cruz
- Fachbereich Physik, Freie Universität Berlin, Berlin 14195, Germany
| | - K Ataka
- Fachbereich Physik, Freie Universität Berlin, Berlin 14195, Germany
| | - J Heberle
- Fachbereich Physik, Freie Universität Berlin, Berlin 14195, Germany
- Forschungsbau SupraFAB, Freie Universität Berlin, Berlin 14195, Germany
| | - J Kozuch
- Fachbereich Physik, Freie Universität Berlin, Berlin 14195, Germany
- Forschungsbau SupraFAB, Freie Universität Berlin, Berlin 14195, Germany
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4
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Feng RR, Wang M, Zhang W, Gai F. Unnatural Amino Acids for Biological Spectroscopy and Microscopy. Chem Rev 2024; 124:6501-6542. [PMID: 38722769 DOI: 10.1021/acs.chemrev.3c00944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
Due to advances in methods for site-specific incorporation of unnatural amino acids (UAAs) into proteins, a large number of UAAs with tailored chemical and/or physical properties have been developed and used in a wide array of biological applications. In particular, UAAs with specific spectroscopic characteristics can be used as external reporters to produce additional signals, hence increasing the information content obtainable in protein spectroscopic and/or imaging measurements. In this Review, we summarize the progress in the past two decades in the development of such UAAs and their applications in biological spectroscopy and microscopy, with a focus on UAAs that can be used as site-specific vibrational, fluorescence, electron paramagnetic resonance (EPR), or nuclear magnetic resonance (NMR) probes. Wherever applicable, we also discuss future directions.
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Affiliation(s)
- Ran-Ran Feng
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Manxi Wang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wenkai Zhang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Feng Gai
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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5
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Alvarez-Hernandez JL, Zhang X, Cui K, Deziel AP, Hammes-Schiffer S, Hazari N, Piekut N, Zhong M. Long-range electrostatic effects from intramolecular Lewis acid binding influence the redox properties of cobalt-porphyrin complexes. Chem Sci 2024; 15:6800-6815. [PMID: 38725508 PMCID: PMC11077573 DOI: 10.1039/d3sc06177a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 04/02/2024] [Indexed: 05/12/2024] Open
Abstract
A CoII-porphyrin complex (1) with an appended aza-crown ether for Lewis acid (LA) binding was synthesized and characterized. NMR spectroscopy and electrochemistry show that cationic group I and II LAs (i.e., Li+, Na+, K+, Ca2+, Sr2+, and Ba2+) bind to the aza-crown ether group of 1. The binding constant for Li+ is comparable to that observed for a free aza-crown ether. LA binding causes an anodic shift in the CoII/CoI couple of between 10 and 40 mV and also impacts the CoIII/CoII couple. The magnitude of the anodic shift of the CoII/CoI couple varies linearly with the strength of the LA as determined by the pKa of the corresponding metal-aqua complex, with dications giving larger shifts than monocations. The extent of the anodic shift of the CoII/CoI couple also increases as the ionic strength of the solution decreases. This is consistent with electric field effects being responsible for the changes in the redox properties of 1 upon LA binding and provides a novel method to tune the reduction potential. Density functional theory calculations indicate that the bound LA is 5.6 to 6.8 Å away from the CoII ion, demonstrating that long-range electrostatic effects, which do not involve changes to the primary coordination sphere, are responsible for the variations in redox chemistry. Compound 1 was investigated as a CO2 reduction electrocatalyst and shows high activity but rapid decomposition.
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Affiliation(s)
| | - Xiaowei Zhang
- Department of Chemical and Environmental Engineering, Yale University New Haven CT 06520 USA
| | - Kai Cui
- Department of Chemistry, Princeton University Princeton NJ 08544 USA
| | | | | | - Nilay Hazari
- Department of Chemistry, Yale University New Haven CT 06520 USA
| | - Nicole Piekut
- Department of Chemistry, Yale University New Haven CT 06520 USA
| | - Mingjiang Zhong
- Department of Chemical and Environmental Engineering, Yale University New Haven CT 06520 USA
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6
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Gonzalez BD, Forbrig E, Yao G, Kielb P, Mroginski MA, Hildebrandt P, Kozuch J. Cation Dependence of Enniatin B/Membrane-Interactions Assessed Using Surface-Enhanced Infrared Absorption (SEIRA) Spectroscopy. Chempluschem 2024:e202400159. [PMID: 38700478 DOI: 10.1002/cplu.202400159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 04/26/2024] [Accepted: 04/29/2024] [Indexed: 05/05/2024]
Abstract
Enniatins are mycotoxins with well-known antibacterial, antifungal, antihelmintic and antiviral activity, which have recently come to attention as potential mitochondriotoxic anticancer agents. The cytotoxicity of enniatins is traced back to ionophoric properties, in which the cyclodepsipeptidic structure results in enniatin:cation-complexes of various stoichiometries proposed as membrane-active species. In this work, we employed a combination of surface-enhanced infrared absorption (SEIRA) spectroscopy, tethered bilayer lipid membranes (tBLMs) and density functional theory (DFT)-based computational spectroscopy to monitor the cation-dependence (Mz+=Na+, K+, Cs+, Li+, Mg2+, Ca2+) on the mechanism of enniatin B (EB) incorporation into membranes and identify the functionally relevant EBn : Mz+ complexes formed. We find that Na+ promotes a cooperative incorporation, modelled via an autocatalytic mechanism and mediated by a distorted 2 : 1-EB2 : Na+ complex. K+ (and Cs+) leads to a direct but less efficient insertion into membranes due to the adoption of "ideal" EB2 : K+ sandwich complexes. In contrast, the presence of Li+, Mg2+, and Ca2+ causes a (partial) extraction of EB from the membrane via the formation of "belted" 1 : 1-EB : Mz+ complexes, which screen the cationic charge less efficiently. Our results point to a relevance of the cation dependence for the transport into the malignant cells where the mitochondriotoxic anticancer activity is exerted.
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Affiliation(s)
- Barbara Daiana Gonzalez
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623, Berlin, Germany
| | - Enrico Forbrig
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623, Berlin, Germany
| | - Guiyang Yao
- Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, D-10623, Berlin, Germany
| | - Patrycja Kielb
- Clausius Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstr. 12, D-53115, Bonn, Germany
- Transdisciplinary Research Area', Building Blocks of Matter and Fundamental Interactions (TRA Matter), Universität Bonn, D-53115, Bonn, Germany
| | - Maria Andrea Mroginski
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623, Berlin, Germany
| | - Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin, Sekr. PC14, Straße des 17. Juni 135, D-10623, Berlin, Germany
| | - Jacek Kozuch
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195, Berlin, Germany
- Forschungsbau SupraFAB, Freie Universität Berlin, Altensteinstr. 23a, D-14195, Berlin, Germany
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7
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Sakpal S, Chakrabarty S, Reddy KD, Deshmukh SH, Biswas R, Bagchi S, Ghosh A. Perturbation of Fermi Resonance on Hydrogen-Bonded > C═O: 2D IR Studies of Small Ester Probes. J Phys Chem B 2024. [PMID: 38686937 DOI: 10.1021/acs.jpcb.3c06698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
We utilized linear and 2D infrared spectroscopy to analyze the carbonyl stretching modes of small esters in different solvents. Particularly noteworthy were the distinct carbonyl spectral line shapes in aqueous solutions, prompting our investigation of the underlying factors responsible for these differences. Through our experimental and theoretical calculations, we identified the presence of the hydrogen-bond-induced Fermi resonance as the primary contributor to the varied line shapes of small esters in aqueous solutions. Furthermore, our findings revealed that the skeletal deformation mode plays a crucial role in the Fermi resonance for all small esters. Specifically, the first overtone band of the skeletal deformation mode intensifies when hydrogen bonds form with the carbonyl group of esters, whereas such coupling is rare in aprotic organic solvents. These spectral insights carry significant implications for the utilization of esters as infrared probes in both biological and chemical systems.
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Affiliation(s)
- Sushil Sakpal
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Suranjana Chakrabarty
- Department of Condensed Matter Physics and Materials Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| | - Kambham Devendra Reddy
- Department of Chemistry, Indian Institute of Technology Tirupati, Tirupati, Andhra Pradesh, India 517619
| | - Samadhan H Deshmukh
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Rajib Biswas
- Department of Chemistry, Indian Institute of Technology Tirupati, Tirupati, Andhra Pradesh, India 517619
| | - Sayan Bagchi
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Anup Ghosh
- Department of Condensed Matter Physics and Materials Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata 700106, India
- Department of Chemical Science, Bose Institute, Kolkata 700091, India
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8
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Kirsh JM, Weaver JB, Boxer SG, Kozuch J. Critical Evaluation of Polarizable and Nonpolarizable Force Fields for Proteins Using Experimentally Derived Nitrile Electric Fields. J Am Chem Soc 2024; 146:6983-6991. [PMID: 38415598 PMCID: PMC10941190 DOI: 10.1021/jacs.3c14775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Molecular dynamics (MD) simulations are frequently carried out for proteins to investigate the role of electrostatics in their biological function. The choice of force field (FF) can significantly alter the MD results, as the simulated local electrostatic interactions lack benchmarking in the absence of appropriate experimental methods. We recently reported that the transition dipole moment (TDM) of the popular nitrile vibrational probe varies linearly with the environmental electric field, overcoming well-known hydrogen bonding (H-bonding) issues for the nitrile frequency and, thus, enabling the unambiguous measurement of electric fields in proteins (J. Am. Chem. Soc. 2022, 144 (17), 7562-7567). Herein, we utilize this new strategy to enable comparisons of experimental and simulated electric fields in protein environments. Specifically, previously determined TDM electric fields exerted onto nitrile-containing o-cyanophenylalanine residues in photoactive yellow protein are compared with MD electric fields from the fixed-charge AMBER FF and the polarizable AMOEBA FF. We observe that the electric field distributions for H-bonding nitriles are substantially affected by the choice of FF. As such, AMBER underestimates electric fields for nitriles experiencing moderate field strengths; in contrast, AMOEBA robustly recapitulates the TDM electric fields. The FF dependence of the electric fields can be partly explained by the presence of additional negative charge density along the nitrile bond axis in AMOEBA, which is due to the inclusion of higher-order multipole parameters; this, in turn, begets more head-on nitrile H-bonds. We conclude by discussing the implications of the FF dependence for the simulation of nitriles and proteins in general.
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Affiliation(s)
- Jacob M Kirsh
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Jared Bryce Weaver
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Jacek Kozuch
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
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9
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Ruiz-Pernía JJ, Świderek K, Bertran J, Moliner V, Tuñón I. Electrostatics as a Guiding Principle in Understanding and Designing Enzymes. J Chem Theory Comput 2024; 20:1783-1795. [PMID: 38410913 PMCID: PMC10938506 DOI: 10.1021/acs.jctc.3c01395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/14/2024] [Accepted: 02/14/2024] [Indexed: 02/28/2024]
Abstract
Enzyme design faces challenges related to the implementation of the basic principles that govern the catalytic activity in natural enzymes. In this work, we revisit basic electrostatic concepts that have been shown to explain the origin of enzymatic efficiency like preorganization and reorganization. Using magnitudes such as the electrostatic potential and the electric field generated by the protein, we explain how these concepts work in different enzymes and how they can be used to rationalize the consequences of point mutations. We also discuss examples of protein design in which electrostatic effects have been implemented. For the near future, molecular simulations, coupled with the use of machine learning methods, can be used to implement electrostatics as a guiding principle for enzyme designs.
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Affiliation(s)
| | - Katarzyna Świderek
- Biocomp
group, Institute of Advanced Materials (INAM), Universitat Jaume I, 12071 Castellón Spain
| | - Joan Bertran
- Departament
de Química, Universitat Autònoma
de Barcelona, 08193 Bellaterra, Spain
| | - Vicent Moliner
- Biocomp
group, Institute of Advanced Materials (INAM), Universitat Jaume I, 12071 Castellón Spain
| | - Iñaki Tuñón
- Departament
de Química Física, Universitat
de València, 46100 Burjassot, Spain
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10
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Hou J, Xu B, Lu Q. Influence of electric double layer rigidity on CO adsorption and electroreduction rate. Nat Commun 2024; 15:1926. [PMID: 38431637 PMCID: PMC10908862 DOI: 10.1038/s41467-024-46318-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 02/21/2024] [Indexed: 03/05/2024] Open
Abstract
Understanding the structure of the electric double layer (EDL) is critical for designing efficient electrocatalytic processes. However, the interplay between reactant adsorbates and the concentrated ionic species within the EDL remains an aspect that has yet to be fully explored. In the present study, we employ electrochemical CO reduction on Cu as a model reaction to reveal the significant impact of EDL structure on CO adsorption. By altering the sequence of applying negative potential and elevating CO pressure, we discern two distinct EDL structures with varying cation density and CO coverage. Our findings demonstrate that the EDL comprising densely packed cations substantially hinders CO adsorption on the Cu as opposed to the EDL containing less compact cations. These two different EDL structures remained stable over the course of our experiments, despite their identical initial and final conditions, suggesting an insurmountable kinetic barrier present in between. Moreover, we show that the size and identity of cations play decisive roles in determining the properties of the EDL in CO electroreduction on Cu. This study presents a refined adaptation of the classical Gouy-Chapman-Stern model and highlights its catalytic importance, which bridges the mechanistic gap between the EDL structure and cathodic reactions.
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Affiliation(s)
- Jiajie Hou
- State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, 100084, Beijing, China
| | - Bingjun Xu
- College of Chemistry and Molecular Engineering, Peking University, 100871, Beijing, China.
| | - Qi Lu
- State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, 100084, Beijing, China.
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11
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Blain-Hartung M, Johannes von Sass G, Plaickner J, Katz S, Tu Hoang O, Andrea Mroginski M, Esser N, Budisa N, Forest KT, Hildebrandt P. On the Role of a Conserved Tryptophan in the Chromophore Pocket of Cyanobacteriochrome. J Mol Biol 2024; 436:168227. [PMID: 37544357 DOI: 10.1016/j.jmb.2023.168227] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 07/26/2023] [Accepted: 07/31/2023] [Indexed: 08/08/2023]
Abstract
The cyanobacteriochrome Slr1393 can be photoconverted between a red (Pr) and green absorbing form (Pg). The recently determined crystal structures of both states suggest a major movement of Trp496 from a stacking interaction with ring D of the phycocyanobilin (PCB) chromophore in Pr to a position outside the chromophore pocket in Pg. Here, we investigated the role of this amino acid during photoconversion in solution using engineered protein variants in which Trp496 was substituted by natural and non-natural amino acids. These variants and the native protein were studied by various spectroscopic techniques (UV-vis absorption, fluorescence, IR, NIR and UV resonance Raman) complemented by theoretical approaches. Trp496 is shown to affect the electronic transition of PCB and to be essential for the thermal equilibrium between Pr and an intermediate state O600. However, Trp496 is not required to stabilize the tilted orientation of ring D in Pr, and does not play a role in the secondary structure changes of Slr1393 during the Pr/Pg transition. The present results confirm the re-orientation of Trp496 upon Pr → Pg conversion, but do not provide evidence of a major change in the microenvironment of this residue. Structural models indicate the penetration of water molecules into the chromophore pocket in both Pr and Pg states and thus water-Trp contacts, which can readily account for the subtle spectral changes between Pr and Pg. Thus, we conclude that reorientation of Trp496 during the Pr-to-Pg photoconversion in solution is not associated with a major change in the dielectric environment in the two states.
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Affiliation(s)
- Matthew Blain-Hartung
- Technische Universität Berlin, Institut für Chemie, Sekr. PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Georg Johannes von Sass
- Technische Universität Berlin, Institut für Chemie, Sekr. CL1, Müller-Breslau-Str.10, D-10623 Berlin, Germany
| | - Julian Plaickner
- Technische Universität Berlin, Institut für Festkörperphysik, Sekr. EW 6-1, Hardenbergstraße 36, 10623 Berlin, Germany
| | - Sagie Katz
- Technische Universität Berlin, Institut für Chemie, Sekr. PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Oanh Tu Hoang
- Technische Universität Berlin, Institut für Chemie, Sekr. PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Maria Andrea Mroginski
- Technische Universität Berlin, Institut für Chemie, Sekr. PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Norbert Esser
- Technische Universität Berlin, Institut für Festkörperphysik, Sekr. EW 6-1, Hardenbergstraße 36, 10623 Berlin, Germany; Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V, Schwarzschildstraße 8, 12489 Berlin, Germany
| | - Nediljko Budisa
- Technische Universität Berlin, Institut für Chemie, Sekr. CL1, Müller-Breslau-Str.10, D-10623 Berlin, Germany; Department of Chemistry, University of Manitoba, 144 Dysart Rd, 360 Parker Building, R3T 2N2 Winnipeg, Manitoba, Canada
| | - Katrina T Forest
- University of Wisconsin-Madison, Department of Bacteriology, 1550 Linden Dr., Madison, WI 53706, USA
| | - Peter Hildebrandt
- Technische Universität Berlin, Institut für Chemie, Sekr. PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany.
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12
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Migliore A, Messina A. Controlling the charge-transfer dynamics of two-level systems around avoided crossings. J Chem Phys 2024; 160:084112. [PMID: 38415830 DOI: 10.1063/5.0188749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Accepted: 02/01/2024] [Indexed: 02/29/2024] Open
Abstract
Two-level quantum systems are fundamental physical models that continue to attract growing interest due to their crucial role as a building block of quantum technologies. The exact analytical solution of the dynamics of these systems is central to control theory and its applications, such as that to quantum computing. In this study, we reconsider the two-state charge transfer problem by extending and using a methodology developed to study (pseudo)spin systems in quantum electrodynamics contexts. This approach allows us to build a time evolution operator for the charge transfer system and to show new opportunities for the coherent control of the system dynamics, with a particular emphasis on the critical dynamic region around the transition state coordinate, where the avoided crossing of the energy levels occurs. We identify and propose possible experimental implementations of a class of rotations of the charge donor (or acceptor) that endow the electronic coupling matrix element with a time-dependent phase that can be employed to realize controllable coherent dynamics of the system across the avoided level crossing. The analogy of these rotations to reference frame rotations in generalized semiclassical Rabi models is discussed. We also show that the physical rotations in the charge-transfer systems can be performed so as to implement quantum gates relevant to quantum computing. From an exquisitely physical-mathematical viewpoint, our approach brings to light situations in which the time-dependent state of the system can be obtained without resorting to the special functions appearing in the Landau-Zener approach.
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Affiliation(s)
- Agostino Migliore
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Antonino Messina
- Dipartimento di Matematica e Informatica, Università degli Studi di Palermo, Via Archirafi, 34, I-90123 Palermo, Italy
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13
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Banerji LC, Jang H, Gardner AM, Cowan AJ. Studying the cation dependence of CO 2 reduction intermediates at Cu by in situ VSFG spectroscopy. Chem Sci 2024; 15:2889-2897. [PMID: 38404396 PMCID: PMC10882457 DOI: 10.1039/d3sc05295h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 01/16/2024] [Indexed: 02/27/2024] Open
Abstract
The nature of the electrolyte cation is known to have a significant impact on electrochemical reduction of CO2 at catalyst|electrolyte interfaces. An understanding of the underlying mechanism responsible for catalytic enhancement as the alkali metal cation group is descended is key to guide catalyst development. Here, we use in situ vibrational sum frequency generation (VSFG) spectroscopy to monitor changes in the binding modes of the CO intermediate at the electrochemical interface of a polycrystalline Cu electrode during CO2 reduction as the electrolyte cation is varied. A CObridge mode is observed only when using Cs+, a cation that is known to facilitate CO2 reduction on Cu, supporting the proposed involvement of CObridge sites in CO coupling mechanisms during CO2 reduction. Ex situ measurements show that the cation dependent CObridge modes correlate with morphological changes of the Cu surface.
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Affiliation(s)
- Liam C Banerji
- Department of Chemistry, Stephenson Institute for Renewable Energy, University of Liverpool Liverpool UK
| | - Hansaem Jang
- Department of Chemistry, Stephenson Institute for Renewable Energy, University of Liverpool Liverpool UK
| | - Adrian M Gardner
- Department of Chemistry, Stephenson Institute for Renewable Energy, University of Liverpool Liverpool UK
- Early Career Laser Laboratory, University of Liverpool Liverpool UK
| | - Alexander J Cowan
- Department of Chemistry, Stephenson Institute for Renewable Energy, University of Liverpool Liverpool UK
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14
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Li R, Yoc-Bautista MG, Weng S, Cai Z, Zhao B, Cronin SB. Voltage-Induced Inversion of Band Bending and Photovoltages at Semiconductor/Liquid Interfaces. ACS APPLIED MATERIALS & INTERFACES 2024; 16:9355-9361. [PMID: 38319802 DOI: 10.1021/acsami.3c14116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
At semiconductor/liquid interfaces, the surface potential and photovoltages are produced by a combination of band bending and quasi-Fermi-level splitting at the semiconductor surface, which are usually treated in a qualitative fashion. As such, it is important to develop quantitative metrics for the band energies and photovoltaics at these interfaces. Here, we present a spectroscopic method for monitoring the photovoltages produced at semiconductor/liquid junctions. The surface reporter molecule mercaptobenzonitrile (MBN) is functionalized on the photoelectrode surface (p-type silicon) and is measured using in situ surface-enhanced Raman scattering (SERS) spectroscopy with a water immersion lens under electrochemical working conditions. In particular, the vibrational frequency of the C≡N stretch mode (ωCN) around 2225 cm-1 is sensitive to the local electric field in solution at the electrode/electrolyte interface via the vibrational Stark effect. Over the applied potential range from -0.8 to 0.6 V vs Ag/AgCl, we observe ωCN to increase from 2220 to 2229 cm-1 (at low laser power). As the incident laser power is increased from 83.5 μW to 13.3 mW, we observe additional shifts of ΔωCN = ±1 cm-1, corresponding to photovoltages produced at the semiconductor/liquid interface ΔV = ±0.2 V. Based on Mott-Schottky measurements, the flat band potential (FBP) occurs at -0.39 V vs Ag/AgCl. For applied potentials above the FBP, we observe ΔωCN > 0 (i.e., blue-shifts ∼1 cm-1) corresponding to positive photovoltages, whereas for applied potentials below the flat band potential, we observe ΔωCN < 0 (i.e., red-shifts ∼1 cm-1) corresponding to negative photovoltages. These spectroscopic observations reveal voltage-induced changes in the band bending at the semiconductor/liquid junction that, thus far, have been difficult to measure.
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15
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Puro RL, Gray TP, Kapfunde TA, Richter-Addo GB, Raschke MB. Vibrational Coupling Infrared Nanocrystallography. NANO LETTERS 2024; 24:1909-1915. [PMID: 38315708 DOI: 10.1021/acs.nanolett.3c03958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Coupling between molecular vibrations leads to collective vibrational states with spectral features sensitive to local molecular order. This provides spectroscopic access to the low-frequency intermolecular energy landscape. In its nanospectroscopic implementation, this technique of vibrational coupling nanocrystallography (VCNC) offers information on molecular disorder and domain formation with nanometer spatial resolution. However, deriving local molecular order relies on prior knowledge of the transition dipole magnitude and crystal structure of the underlying ordered phase. Here we develop a quantitative model for VCNC by relating nano-FTIR collective vibrational spectra to the molecular crystal structure from X-ray crystallography. We experimentally validate our approach at the example of a metal organic porphyrin complex with a carbonyl ligand as the probe vibration. This framework establishes VCNC as a powerful tool for measuring low-energy molecular interactions, wave function delocalization, nanoscale disorder, and domain formation in a wide range of molecular systems.
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Affiliation(s)
- Richard L Puro
- Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309, United States
| | - Thomas P Gray
- Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309, United States
| | - Tsitsi A Kapfunde
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - George B Richter-Addo
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Markus B Raschke
- Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309, United States
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16
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Sumner E, Pižl M, McQuaid KT, Hartl F. Nitrile Substituents at the Conjugated Dipyridophenazine Moiety as Infrared Redox Markers in Electrochemically Reduced Heteroleptic Ru(II) Polypyridyl Complexes. Inorg Chem 2024; 63:2460-2469. [PMID: 38262043 PMCID: PMC10848246 DOI: 10.1021/acs.inorgchem.3c03484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 01/05/2024] [Accepted: 01/09/2024] [Indexed: 01/25/2024]
Abstract
Ruthenium(II) complexes [Ru(tap)2(NN)]2+ (tap = 1,4,5,8-tetraazaphenanthrene, NN = 11-cyano-dipyrido[3,2-a:2',3'-c]phenazine (11-CN-dppz) and 11,12-dicyano-dipyrido[3,2-a:2',3'-c]phenazine (11,12-CN-dppz)) feature the C≡N groups as infrared (IR)-active redox markers. They were studied by cyclic voltammetry, UV-vis, and IR spectroelectrochemistry (SEC), and density functional theory calculations to assign the four 1e- reduction waves R1-R4 observed in dichloromethane. Generally, the NN ligands are reduced first (R1). For [Ru(tap)2(11,12-CN-dppz)]2+, R1 is sufficiently separated from R2 and delocalized over both tap ligands. Accordingly, IR SEC conducted at R1 shows a large red shift of the νs,as(C≡N) modes by -18/-28 cm-1, accompanied by a 4-fold enhancement of the νs(C≡N) intensity, comparably with reference data for free 11,12-CN-dppz. The first tap-based reduction of spin-doublet [Ru(tap)2(11,12-CN-dppz)]+ to spin-triplet [Ru(tap)2(11,12-CN-dppz)] at R2 decreased ν(C≡N) by merely -2 cm-1, while the intensity enhancement reached an overall factor of 8. Comparably, a red shift of ν(C≡N) by -27 cm-1 resulted from the 1e- reduction of [Ru(tap)2(11-CN-dppz)]2+ at R1 (poorly resolved from R2), and the intensity enhancement was roughly 3-fold. Concomitant 1e- reductions of the tap ligands (R2 and R3) caused only minor ν(C≡N) shifts of -3 cm-1 and increased the absorbance by overall factors of 6.5 and 8, respectively.
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Affiliation(s)
- Elizabeth Sumner
- Department
of Chemistry, University of Reading, Whiteknights, Reading RG6 6DX, U.K.
| | - Martin Pižl
- Department
of Chemistry, University of Reading, Whiteknights, Reading RG6 6DX, U.K.
- Department
of Inorganic Chemistry, University of Chemistry
and Technology Prague, Technická 5, Prague 6 166 28, Czech Republic
| | - Kane T. McQuaid
- Department
of Chemistry, University of Reading, Whiteknights, Reading RG6 6DX, U.K.
| | - František Hartl
- Department
of Chemistry, University of Reading, Whiteknights, Reading RG6 6DX, U.K.
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17
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Pathak B, Kesari S, Patwari GN. Enticing a Proton using Single Ammonia Molecule as Bait. J Phys Chem B 2024; 128:1022-1028. [PMID: 38240575 DOI: 10.1021/acs.jpcb.3c06761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
In microhydrated acid-solvent clusters, deprotonation of an acid is assisted by a critical number of solvent molecules and a solvent electric field. Born-Oppenheimer molecular dynamics simulations reveal that trifluoroacetic acid undergoes spontaneous proton transfer in water clusters, with the critical number being five. Acetic acid and phenol, on the other hand, do not dissociate even in the presence of a large number of water molecules (in excess of 40). The addition of a single ammonia molecule to the water cluster, which interacts directly with the protic group, lowers the critical number of solvent water molecules required for proton transfer to three and seven in the case of acetic acid and phenol, respectively. The population of the undissociated and the proton-transferred structures get dispersed to form separate islands on the electric field versus the O-H distance representation with the cusp representing the critical values. The critical electric fields for the spontaneous proton transfer are around 254, 237, and 318 MV cm-1 for trifluoroacetic acid, acetic acid, and phenol, respectively. In the case of phenol, the free energy profiles suggest that proton transfer to the ammonia moiety embedded in water promotes proton transfer efficiently due to the higher basicity of ammonia and enhanced hydrogen bonding network of solvent water, vis-à-vis phenol-ammonia clusters.
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Affiliation(s)
- Bijaya Pathak
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Shaivi Kesari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - G Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
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18
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He H, Yin J, Li M, Dessai CVP, Yi M, Teng X, Zhang M, Li Y, Du Z, Xu B, Cheng JX. Mapping enzyme activity in living systems by real-time mid-infrared photothermal imaging of nitrile chameleons. Nat Methods 2024; 21:342-352. [PMID: 38191931 PMCID: PMC11165695 DOI: 10.1038/s41592-023-02137-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 11/17/2023] [Indexed: 01/10/2024]
Abstract
Simultaneous spatial mapping of the activity of multiple enzymes in a living system can elucidate their functions in health and disease. However, methods based on monitoring fluorescent substrates are limited. Here, we report the development of nitrile (C≡N)-tagged enzyme activity reporters, named nitrile chameleons, for the peak shift between substrate and product. To image these reporters in real time, we developed a laser-scanning mid-infrared photothermal imaging system capable of imaging the enzymatic substrates and products at a resolution of 300 nm. We show that when combined, these tools can map the activity distribution of different enzymes and measure their relative catalytic efficiency in living systems such as cancer cells, Caenorhabditis elegans, and brain tissues, and can be used to directly visualize caspase-phosphatase interactions during apoptosis. Our method is generally applicable to a broad category of enzymes and will enable new analyses of enzymes in their native context.
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Affiliation(s)
- Hongjian He
- Department of Electrical and Computer Engineering, Boston University, Boston, MA, USA
- Photonics Center, Boston University, Boston, MA, USA
| | - Jiaze Yin
- Department of Electrical and Computer Engineering, Boston University, Boston, MA, USA
- Photonics Center, Boston University, Boston, MA, USA
| | - Mingsheng Li
- Department of Electrical and Computer Engineering, Boston University, Boston, MA, USA
- Photonics Center, Boston University, Boston, MA, USA
| | - Chinmayee Vallabh Prabhu Dessai
- Photonics Center, Boston University, Boston, MA, USA
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Meihui Yi
- Department of Chemistry, Brandeis University, Waltham, MA, USA
| | - Xinyan Teng
- Photonics Center, Boston University, Boston, MA, USA
- Department of Chemistry, Boston University, Boston, MA, USA
| | - Meng Zhang
- Photonics Center, Boston University, Boston, MA, USA
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Yueming Li
- Photonics Center, Boston University, Boston, MA, USA
- Department of Mechanical Engineering, Boston University, Boston, MA, USA
| | - Zhiyi Du
- Photonics Center, Boston University, Boston, MA, USA
- Department of Chemistry, Boston University, Boston, MA, USA
| | - Bing Xu
- Department of Chemistry, Brandeis University, Waltham, MA, USA
| | - Ji-Xin Cheng
- Department of Electrical and Computer Engineering, Boston University, Boston, MA, USA.
- Photonics Center, Boston University, Boston, MA, USA.
- Department of Biomedical Engineering, Boston University, Boston, MA, USA.
- Department of Chemistry, Boston University, Boston, MA, USA.
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19
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Yang YX, Yang XH, Huang ML, Wu LW, Liu Z, Cheng J, Huang YF. In Situ Spectroscopic Elucidation of the Electrochemical Potential Drop at Polyelectrolytes/Au Interfaces. J Phys Chem Lett 2024; 15:701-706. [PMID: 38214464 DOI: 10.1021/acs.jpclett.3c03111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
Polyelectrolytes have been widely applied in electrochemical devices. Understanding the polyelectrolyte/electrode interfaces is pivotal for polyelectrolyte-based applications. Here, we measured the electrochemical potential drop and the local activity of the mobile ion of H+ or OH- at the polyelectrolytes/Au interfaces by in situ electrochemical surface-enhanced Raman spectroscopy and voltammetry in three-electrode cells. We found that the potential dependences of the electrochemical potential drop in polyelectrolytes were smaller than that in conventional electrolyte solutions. The interfacial activity of H+ or OH- was much lower than that of bulk polyelectrolytes. The potential-dependent molecular dynamics simulations showed that the mobility of ionomers of polyelectrolytes in an electrostatic field was limited by a polymer matrix. These results suggested a characteristically thicker compact layer in the electrical double layer of a polyelectrolyte/electrode interface due to the accumulation of mobile H+ or OH- with a thicker hydration layer and immobile ionomers.
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Affiliation(s)
- Yun-Xiao Yang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, P. R. China
| | - Xiao-Hui Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Mo-Li Huang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, P. R. China
| | - Li-Wen Wu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, P. R. China
| | - Zhi Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, P. R. China
- Center for Transformative Science, ShanghaiTech University, Shanghai 201210, P. R. China
| | - Jun Cheng
- State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361005, P. R. China
| | - Yi-Fan Huang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, P. R. China
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20
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Zhou L, Feng RR, Zhang W, Gai F. Triple-Bond Vibrations: Emerging Applications in Energy and Biological Sciences. J Phys Chem Lett 2024; 15:187-200. [PMID: 38156972 DOI: 10.1021/acs.jpclett.3c02619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Triple bonds, such as that formed between two carbon atoms (i.e., C≡C) or that formed between one carbon atom and one nitrogen atom (i.e., C≡N), afford unique chemical bonding and hence vibrational characteristics. As such, they are not only frequently used to construct molecules with tailored chemical and/or physical properties but also employed as vibrational probes to provide site-specific chemical and/or physical information at the molecular level. Herein, we offer our perspective on the emerging applications of various triple-bond vibrations in energy and biological sciences with a focus on C≡C and C≡N triple bonds.
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Affiliation(s)
- Liang Zhou
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Ran-Ran Feng
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wenkai Zhang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Feng Gai
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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21
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Jermusek FA, Webb LJ. Electrostatic Impact of Brefeldin A on Thiocyanate Probes Surrounding the Interface of Arf1-BFA-ARNO4M, a Protein-Drug-Protein Complex. Biochemistry 2024; 63:27-41. [PMID: 38078826 DOI: 10.1021/acs.biochem.3c00366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Protein-protein interactions regulate many cellular processes, making them ideal drug candidates. Design of such drugs, however, is hindered by a lack of understanding of the factors that contribute to the interaction specificity. Specific protein-protein complexes possess both structural and electrostatic complementarity, and while structural complementarity of protein complexes has been extensively investigated, fundamental understanding of the complicated networks of electrostatic interactions at these interfaces is lacking, thus hindering the rational design of orthosterically binding small molecules. To better understand the electrostatic interactions at protein interfaces and how a small molecule could contribute to and fit within that environment, we used a model protein-drug-protein system, Arf1-BFA-ARNO4M, to investigate how small molecule brefeldin A (BFA) perturbs the Arf1-ARNO4M interface. By using nitrile probe labeled Arf1 sites and measuring vibrational Stark effects as well as temperature dependent infrared shifts, we measured changes in the electric field and hydrogen bonding at this interface upon BFA binding. At all five probe locations of Arf1, we found that the vibrational shifts resulting from BFA binding corroborate trends found in Poisson-Boltzmann calculations of surface potentials of Arf1-ARNO4M and Arf1-BFA-ARNO4M, where BFA contributes negative electrostatic potential to the protein interface. The data also corroborate previous hypotheses about the mechanism of interfacial binding and confirm that alternating patches of hydrophobic and polar interactions lead to BFA binding specificity. These findings demonstrate the impact of BFA on this protein-protein interface and have implications for the design of other interfacial drug candidates.
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Affiliation(s)
- Frank A Jermusek
- Interdisciplinary Life Sciences Graduate Program, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Lauren J Webb
- Department of Chemistry and Interdisciplinary Life Sciences Graduate Program, The University of Texas at Austin, Austin, Texas 78712, United States
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22
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Jiang Y, Ding N, Shao Q, Stull SL, Cheng Z, Yang ZJ. Substrate Positioning Dynamics Involves a Non-Electrostatic Component to Mediate Catalysis. J Phys Chem Lett 2023; 14:11480-11489. [PMID: 38085952 PMCID: PMC11211065 DOI: 10.1021/acs.jpclett.3c02444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Substrate positioning dynamics (SPD) orients the substrate in the active site, thereby influencing catalytic efficiency. However, it remains unknown whether SPD effects originate primarily from electrostatic perturbation inside the enzyme or can independently mediate catalysis with a significant non-electrostatic component. In this work, we investigated how the non-electrostatic component of SPD affects transition state (TS) stabilization. Using high-throughput enzyme modeling, we selected Kemp eliminase variants with similar electrostatics inside the enzyme but significantly different SPD. The kinetic parameters of these mutants were experimentally characterized. We observed a valley-shaped, two-segment linear correlation between the TS stabilization free energy (converted from kinetic parameters) and substrate positioning index (a metric to quantify SPD). The energy varies by approximately 2 kcal/mol. Favorable SPD was observed for the distal mutant R154W, increasing the proportion of reactive conformations and leading to the lowest activation free energy. These results indicate the substantial contribution of the non-electrostatic component of SPD to enzyme catalytic efficiency.
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Affiliation(s)
- Yaoyukun Jiang
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Ning Ding
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Qianzhen Shao
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Sebastian L. Stull
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Zihao Cheng
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Zhongyue J. Yang
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
- Data Science Institute, Vanderbilt University, Nashville, Tennessee 37235, United States
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States
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23
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Bodine M, Rozyyev V, Elam JW, Tokmakoff A, Lewis NHC. Vibrational Probe at the Electrochemical Interface: Dependence on Plasmon Coupling and Potential of the Lineshape in Two-Dimensional Infrared Spectroscopy. J Phys Chem Lett 2023:11092-11099. [PMID: 38051916 DOI: 10.1021/acs.jpclett.3c02987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Two-dimensional infrared spectroscopy of vibrational probes at an electrode surface shows promise for studying the structural dynamics at an active electrochemical interface. This interface is a complex environment where the solution structures in response to the applied potential. A strategy for achieving the necessary monolayer sensitivity is to use a plasmonically active electrode, which enhances the electromagnetic fields that produce the spectroscopic response. Here, we show how the coupling between the plasmon and the vibrations of the molecular monolayer impacts the FTIR and 2D IR spectroscopy, with an emphasis on the electrochemical potential difference spectra. We show how mixing between the vibrational and plasmonic states gives rise to the distortions that are observed in these measurements. This provides an important step toward 2D IR measurements of vibrational probes at the electrochemical interface as a tool for probing the structural dynamics in the double layer.
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Affiliation(s)
- Melissa Bodine
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Vepa Rozyyev
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
- Applied Materials Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Jeffrey W Elam
- Applied Materials Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Nicholas H C Lewis
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
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24
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Zheng C, Ji Z, Mathews II, Boxer SG. Enhanced active-site electric field accelerates enzyme catalysis. Nat Chem 2023; 15:1715-1721. [PMID: 37563323 PMCID: PMC10906027 DOI: 10.1038/s41557-023-01287-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 06/29/2023] [Indexed: 08/12/2023]
Abstract
The design and improvement of enzymes based on physical principles remain challenging. Here we demonstrate that the principle of electrostatic catalysis can be leveraged to substantially improve a natural enzyme's activity. We enhanced the active-site electric field in horse liver alcohol dehydrogenase by replacing the serine hydrogen-bond donor with threonine and replacing the catalytic Zn2+ with Co2+. Based on the electric field enhancement, we make a quantitative prediction of rate acceleration-50-fold faster than the wild-type enzyme-which was in close agreement with experimental measurements. The effects of the hydrogen bonding and metal coordination, two distinct chemical forces, are described by a unified physical quantity-electric field, which is quantitative, and shown here to be additive and predictive. These results suggest a new design paradigm for both biological and non-biological catalysts.
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Affiliation(s)
- Chu Zheng
- Department of Chemistry, Stanford University, Stanford, CA, USA
| | - Zhe Ji
- Department of Chemistry, Stanford University, Stanford, CA, USA
| | | | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, CA, USA.
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25
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Baserga F, Storm J, Schlesinger R, Heberle J, Stripp ST. The catalytic reaction of cytochrome c oxidase probed by in situ gas titrations and FTIR difference spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:149000. [PMID: 37516233 DOI: 10.1016/j.bbabio.2023.149000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 06/22/2023] [Accepted: 07/24/2023] [Indexed: 07/31/2023]
Abstract
Cytochrome c oxidase (CcO) is a transmembrane heme‑copper metalloenzyme that catalyzes the reduction of O2 to H2O at the reducing end of the respiratory electron transport chain. To understand this reaction, we followed the conversion of CcO from Rhodobacter sphaeroides between several active-ready and carbon monoxide-inhibited states via attenuated total reflection Fourier-transform infrared (ATR FTIR) difference spectroscopy. Utilizing a novel gas titration setup, we prepared the mixed-valence, CO-inhibited R2CO state as well as the fully-reduced R4 and R4CO states and induced the "active ready" oxidized state OH. These experiments are performed in the dark yielding FTIR difference spectra exclusively triggered by exposure to O2, the natural substrate of CcO. Our data demonstrate that the presence of CO at heme a3 does not impair the catalytic oxidation of CcO when the cycle starts from the fully-reduced states. Interestingly, when starting from the R2CO state, the release of the CO ligand upon purging with inert gas yield a product that is indistinguishable from photolysis-induced states. The observed changes at heme a3 in the catalytic binuclear center (BNC) result from the loss of CO and are unrelated to electronic excitation upon illumination. Based on our experiments, we re-evaluate the assignment of marker bands that appear in time-resolved photolysis and perfusion-induced experiments on CcO.
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Affiliation(s)
- Federico Baserga
- Freie Universität Berlin, Experimental Molecular Biophysics, Arnimallee 14, D-14195 Berlin, Germany
| | - Julian Storm
- Freie Universität Berlin, Genetic Biophysics, Arnimallee 14, D-14195 Berlin, Germany
| | - Ramona Schlesinger
- Freie Universität Berlin, Genetic Biophysics, Arnimallee 14, D-14195 Berlin, Germany
| | - Joachim Heberle
- Freie Universität Berlin, Experimental Molecular Biophysics, Arnimallee 14, D-14195 Berlin, Germany
| | - Sven T Stripp
- Freie Universität Berlin, Experimental Molecular Biophysics, Arnimallee 14, D-14195 Berlin, Germany; Technische Universität Berlin, Division of Physical Chemistry, Strasse des 17. Juni 115, D-10623 Berlin, Germany.
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26
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Lake WR, Meng J, Dawlaty JM, Lian T, Hammes-Schiffer S. Electro-inductive Effect Dominates Vibrational Frequency Shifts of Conjugated Probes on Gold Electrodes. J Am Chem Soc 2023; 145:22548-22554. [PMID: 37795975 DOI: 10.1021/jacs.3c07489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
Interfacial electric fields play a critical role in electrocatalysis and are often characterized by using vibrational probes attached to an electrode surface. Understanding the physical principles dictating the impact of the applied electrode potential on the vibrational probe frequency is important. Herein, a comparative study is performed for two molecular probes attached to a gold electrode. Both probes contain a nitrile (CN) group, but 4-mercaptobenzonitrile (4-MBN) exhibits continuous conjugation from the electrode through the nitrile group, whereas this conjugation is interrupted for 2-(4-mercaptophenyl)acetonitrile (4-MPCN). Periodic density functional theory calculations predict that the CN vibrational frequency shift of the 4-MBN system is dominated by induction, which is a through-bond polarization effect, leading to a strong potential dependence that does not depend significantly on the orientation of the CN bond relative to the surface. In contrast, the CN vibrational frequency shift of the 4-MPCN system is influenced less by induction and more by through-space electric field effects, leading to a weaker potential dependence and a greater orientation dependence. These theoretical predictions were confirmed by surface-enhanced Raman spectroscopy experiments. Balancing through-bond and through-space electrostatic effects may assist in the fundamental understanding and design of electrocatalytic systems.
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Affiliation(s)
- William R Lake
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Jinhui Meng
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Jahan M Dawlaty
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Tianquan Lian
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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27
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Sarhangi SM, Matyushov DV. Comment on "Applicability of perturbed matrix method for charge transfer studies at bio/metallic interfaces: a case of azurin" by O. Kontkanen, D. Biriukov and Z. Futera, Phys. Chem. Chem. Phys., 2023, 25, 12479. Phys Chem Chem Phys 2023; 25:26923-26928. [PMID: 37782532 DOI: 10.1039/d3cp03178k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
Polarizability is a fundamental property of all molecular systems describing the deformation of the molecular electronic density in response to an applied electric field. The question of whether polarizability of the active site needs to be included in theories of enzymatic activity remains open. Hybrid quantum mechanical/molecular mechanical calculations are hampered by difficulties faced by many quantum-chemistry algorithms to provide sufficiently accurate estimates of the anisotropic second-rank tensor of molecular polarizability. In this Comment, we provide general theoretical arguments for the values of polarizability of the quantum region or a molecule which have to be reproduced by electronic structure calculations.
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Affiliation(s)
- Setare Mostajabi Sarhangi
- School of Molecular Sciences and Department of Physics, Arizona State University, PO Box 871504, Tempe, Arizona 85287-1504, USA.
| | - Dmitry V Matyushov
- School of Molecular Sciences and Department of Physics, Arizona State University, PO Box 871504, Tempe, Arizona 85287-1504, USA.
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28
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Stitch M, Avagliano D, Graczyk D, Clark IP, González L, Towrie M, Quinn SJ. Good Vibrations Report on the DNA Quadruplex Binding of an Excited State Amplified Ruthenium Polypyridyl IR Probe. J Am Chem Soc 2023; 145:21344-21360. [PMID: 37736878 PMCID: PMC10557146 DOI: 10.1021/jacs.3c06099] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Indexed: 09/23/2023]
Abstract
The nitrile containing Ru(II)polypyridyl complex [Ru(phen)2(11,12-dCN-dppz)]2+ (1) is shown to act as a sensitive infrared probe of G-quadruplex (G4) structures. UV-visible absorption spectroscopy reveals enantiomer sensitive binding for the hybrid htel(K) and antiparallel htel(Na) G4s formed by the human telomer sequence d[AG3(TTAG3)3]. Time-resolved infrared (TRIR) of 1 upon 400 nm excitation indicates dominant interactions with the guanine bases in the case of Λ-1/htel(K), Δ-1/htel(K), and Λ-1/htel(Na) binding, whereas Δ-1/htel(Na) binding is associated with interactions with thymine and adenine bases in the loop. The intense nitrile transient at 2232 cm-1 undergoes a linear shift to lower frequency as the solution hydrogen bonding environment decreases in DMSO/water mixtures. This shift is used as a sensitive reporter of the nitrile environment within the binding pocket. The lifetime of 1 in D2O (ca. 100 ps) is found to increase upon DNA binding, and monitoring of the nitrile and ligand transients as well as the diagnostic DNA bleach bands shows that this increase is related to greater protection from the solvent environment. Molecular dynamics simulations together with binding energy calculations identify the most favorable binding site for each system, which are in excellent agreement with the observed TRIR solution study. This study shows the power of combining the environmental sensitivity of an infrared (IR) probe in its excited state with the TRIR DNA "site effect" to gain important information about the binding site of photoactive agents and points to the potential of such amplified IR probes as sensitive reporters of biological environments.
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Affiliation(s)
- Mark Stitch
- School
of Chemistry, University College Dublin, Dublin, D04 V1W8, Ireland
| | - Davide Avagliano
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 19, 1090 Vienna, Austria
- Department
of Chemistry, Chemical Physics Theory Group, University of Toronto, 80 St. George St., Toronto, Ontario M5S 3H6, Canada
| | - Daniel Graczyk
- School
of Chemistry, University College Dublin, Dublin, D04 V1W8, Ireland
| | - Ian P. Clark
- Central
Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Leticia González
- Institute
of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 19, 1090 Vienna, Austria
- Vienna
Research Platform on Accelerating Photoreaction Discovery, University of Vienna, Währingerstr. 19, 1090 Vienna, Austria
| | - Michael Towrie
- Central
Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, U.K.
| | - Susan J Quinn
- School
of Chemistry, University College Dublin, Dublin, D04 V1W8, Ireland
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29
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Iwahara J, Pettitt BM, Yu B. Direct measurements of biomolecular electrostatics through experiments. Curr Opin Struct Biol 2023; 82:102680. [PMID: 37573815 PMCID: PMC10947535 DOI: 10.1016/j.sbi.2023.102680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 07/19/2023] [Accepted: 07/19/2023] [Indexed: 08/15/2023]
Abstract
Biomolecular electrostatics has been a subject of computational investigations based on 3D structures. This situation is changing because emerging experimental tools allow us to quantitatively investigate biomolecular electrostatics without any use of structure information. Now, electrostatic potentials around biomolecules can directly be measured for many residues simultaneously by nuclear magnetic resonance (NMR) spectroscopy. This NMR method can be used to study electrostatic aspects of various processes, including macromolecular association and liquid-liquid phase separation. Applications to structurally flexible biomolecules such as intrinsically disordered proteins are particularly useful. The new tools also facilitate examination of theoretical models and methods for biomolecular electrostatics.
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Affiliation(s)
- Junji Iwahara
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA.
| | - B Montgomery Pettitt
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Binhan Yu
- Department of Biochemistry & Molecular Biology, Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
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30
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Menachekanian S, Mora Perez C, Pennathur AK, Voegtle MJ, Blauth D, Prezhdo OV, Dawlaty JM. Phenol as a Tethering Group to Gold Surfaces: Stark Response and Comparison to Benzenethiol. J Phys Chem Lett 2023; 14:8353-8359. [PMID: 37702751 PMCID: PMC10518863 DOI: 10.1021/acs.jpclett.3c02058] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 09/07/2023] [Indexed: 09/14/2023]
Abstract
Understanding the adsorption of organic molecules on metals is important in numerous areas of surface science, including electrocatalysis, electrosynthesis, and biosensing. While thiols are commonly used to tether organic molecules on metals, it is desirable to broaden the range of anchoring groups. In this study, we use a combined spectroelectrochemical and computational approach to demonstrate the adsorption of 4-cyanophenols (CPs) on polycrystalline gold. Using the nitrile stretching vibration as a marker, we confirm the adsorption of CP on the gold electrode and compare our results with those obtained for the thiol counterpart, 4-mercaptobenzonitirle (MBN). Our results reveal that CP adsorbs on the gold electrode via the OH linker, as evidenced by the similarity in the direction and magnitude of the nitrite Stark shifts for CP and MBN. This finding paves the way for exploring new approaches to modify electrode surfaces for controlled reactivity. Furthermore, it highlights adsorption on metals as an important step in the electroreactivity of phenols.
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Affiliation(s)
- Sevan Menachekanian
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Carlos Mora Perez
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
- Theoretical
Physics and Chemistry of Materials, Los
Alamos National Laboratory, Los
Alamos, New Mexico 87545, United States
- Center
for Nonlinear Studies, Los Alamos National
Laboratory, Los Alamos, New Mexico 87545, United States
| | - Anuj K. Pennathur
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Mattew J. Voegtle
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Drew Blauth
- Department
of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Oleg V. Prezhdo
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Jahan M. Dawlaty
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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31
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Gopakumar K, Shaik S, Ramanan R. Two-Way Catalysis in a Diels-Alder Reaction Limits Inhibition Induced by an External Electric Field. Angew Chem Int Ed Engl 2023; 62:e202307579. [PMID: 37530131 DOI: 10.1002/anie.202307579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 07/18/2023] [Accepted: 08/01/2023] [Indexed: 08/03/2023]
Abstract
Oriented external electric fields (EEFs) act as catalysts that can induce selectivity in chemical reactions. The responses of the Diels-Alder (DA) reaction between butadiene and ethylene (BDE-DA) as well as cyclopentadiene and ethylene (CPDE-DA) towards EEF stimuli are investigated here using density functional theory (B3LYP) calculations. EEF is a vector that catalyzes the reaction in one direction while inhibiting it in the opposite direction. Here we report that the inhibitive direction becomes rate-enhancing after some increase in the EEF. The EEF value that brings about the maximum possible inhibition for the reaction is defined as the electrostatic resistance point (ERP). The possibility of both normal and inverse electron-demand DA reactions causes catalytic activity in both directions of the EEF starting at a unique ERP value. The C5 substituents of cyclopentadiene control the ERP values depending upon the resistance power that the functional group provides against the EEF. The endo and exo diastereomeric transition states of the DA reaction have distinct ERP values and the difference (ΔERP) provides the through-space electrostatic contribution to the stereoselectivity on a relative scale. Thus, the ERP values can be used as a gauge for the electrostatic interactions between substituent groups and external stimuli.
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Affiliation(s)
- Karthik Gopakumar
- Department of Chemistry, National Institute of Technology, Rourkela, Rourkela, Odisha, 769008, India
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, 9190407, Jerusalem, Israel
| | - Rajeev Ramanan
- Department of Chemistry, National Institute of Technology, Rourkela, Rourkela, Odisha, 769008, India
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32
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Shao Q, Jiang Y, Yang ZJ. EnzyHTP Computational Directed Evolution with Adaptive Resource Allocation. J Chem Inf Model 2023; 63:5650-5659. [PMID: 37611241 PMCID: PMC11211066 DOI: 10.1021/acs.jcim.3c00618] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Directed evolution facilitates enzyme engineering via iterative rounds of mutagenesis. Despite the wide applications of high-throughput screening, building "smart libraries" to effectively identify beneficial variants remains a major challenge in the community. Here, we developed a new computational directed evolution protocol based on EnzyHTP, a software that we have previously reported to automate enzyme modeling. To enhance the throughput efficiency, we implemented an adaptive resource allocation strategy that dynamically allocates different types of computing resources (e.g., GPU/CPU) based on the specific need of an enzyme modeling subtask in the workflow. We implemented the strategy as a Python library and tested the library using fluoroacetate dehalogenase as a model enzyme. The results show that compared to fixed resource allocation where both CPU and GPU are on-call for use during the entire workflow, applying adaptive resource allocation can save 87% CPU hours and 14% GPU hours. Furthermore, we constructed a computational directed evolution protocol under the framework of adaptive resource allocation. The workflow was tested against two rounds of mutational screening in the directed evolution experiments of Kemp eliminase (KE07) with a total of 184 mutants. Using folding stability and electrostatic stabilization energy as computational readout, we identified all four experimentally observed target variants. Enabled by the workflow, the entire computation task (i.e., 18.4 μs MD and 18,400 QM single-point calculations) completes in 3 days of wall-clock time using ∼30 GPUs and ∼1000 CPUs.
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Affiliation(s)
- Qianzhen Shao
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Yaoyukun Jiang
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Zhongyue J. Yang
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
- Data Science Institute, Vanderbilt University, Nashville, Tennessee 37235, United States
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States
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33
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Cassone G, Saija F, Sponer J, Shaik S. The Reactivity-Enhancing Role of Water Clusters in Ammonia Aqueous Solutions. J Phys Chem Lett 2023; 14:7808-7813. [PMID: 37623433 PMCID: PMC10494223 DOI: 10.1021/acs.jpclett.3c01810] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 08/22/2023] [Indexed: 08/26/2023]
Abstract
Among the many prototypical acid-base systems, ammonia aqueous solutions hold a privileged place, owing to their omnipresence in various planets and their universal solvent character. Although the theoretical optimal water-ammonia molar ratio to form NH4+ and OH- ion pairs is 50:50, our ab initio molecular dynamics simulations show that the tendency of forming these ionic species is inversely (directly) proportional to the amount of ammonia (water) in ammonia aqueous solutions, up to a water-ammonia molar ratio of ∼75:25. Here we prove that the reactivity of these liquid mixtures is rooted in peculiar microscopic patterns emerging at the H-bonding scale, where the highly orchestrated motion of 5 solvating molecules modulates proton transfer events through local electric fields. This study demonstrates that the reaction of water with NH3 is catalyzed by a small cluster of water molecules, in which an H atom possesses a high local electric field, much like the effect observed in catalysis by water droplets [ PNAS 2023, 120, e2301206120].
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Affiliation(s)
- Giuseppe Cassone
- Institute
for Physical-Chemical Processes, Italian
National Research Council (CNR-IPCF), Viale Stagno d’Alcontres 37, 98158 Messina, Italy
| | - Franz Saija
- Institute
for Physical-Chemical Processes, Italian
National Research Council (CNR-IPCF), Viale Stagno d’Alcontres 37, 98158 Messina, Italy
| | - Jiri Sponer
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, 61265 Brno, Czechia
| | - Sason Shaik
- Institute
of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel
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34
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Yang Y, Liu J, Feng RR, Zhang W, Gai F. C≡N Stretching Frequency as a Convenient Reporter of Charge Separation in Molecular Systems. J Phys Chem B 2023; 127:6999-7003. [PMID: 37525395 DOI: 10.1021/acs.jpcb.3c02707] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Previously, several studies have shown that, for a set of structurally related nitrile compounds, there could be a linear relationship between the total charge on the nitrile group (qCN) and its stretching frequency (νCN). However, it is unclear whether the corresponding frequency and charge properties of structurally different nitrile compounds can be described by a single linear νCN-qCN relationship. Herein, we compute the qCN magnitudes of a large number of nitrile-containing molecules whose νCN values cover a spectral range of ca. 200 cm-1 and are measured under different experimental conditions. Our results reveal that νCN indeed exhibits a linear dependence on qCN, with a slope of 637 ± 30 cm-1/charge. Because the nitrile moiety is a commonly used building block in electronic donor-acceptor (D-A) molecular systems, we believe that this linear relationship will find utility in a wide range of applications where such D-A constructs are used, such as in organic photovoltaic assemblies. In addition, we apply this linear relationship to characterize the degree of charge transfer upon photoexcitation of two indole derivatives, 5-cyanoindole and 6-cyanoindole, and are able to show that in both cases, the fluorescence emission arises from a charge-transfer or La state.
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Affiliation(s)
- Yuyao Yang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Jingsong Liu
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Ran-Ran Feng
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wenkai Zhang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Feng Gai
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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35
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Chen C, Henderson JN, Ruchkin DA, Kirsh JM, Baranov MS, Bogdanov AM, Mills JH, Boxer SG, Fang C. Structural Characterization of Fluorescent Proteins Using Tunable Femtosecond Stimulated Raman Spectroscopy. Int J Mol Sci 2023; 24:11991. [PMID: 37569365 PMCID: PMC10418586 DOI: 10.3390/ijms241511991] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/19/2023] [Accepted: 07/24/2023] [Indexed: 08/13/2023] Open
Abstract
The versatile functions of fluorescent proteins (FPs) as fluorescence biomarkers depend on their intrinsic chromophores interacting with the protein environment. Besides X-ray crystallography, vibrational spectroscopy represents a highly valuable tool for characterizing the chromophore structure and revealing the roles of chromophore-environment interactions. In this work, we aim to benchmark the ground-state vibrational signatures of a series of FPs with emission colors spanning from green, yellow, orange, to red, as well as the solvated model chromophores for some of these FPs, using wavelength-tunable femtosecond stimulated Raman spectroscopy (FSRS) in conjunction with quantum calculations. We systematically analyzed and discussed four factors underlying the vibrational properties of FP chromophores: sidechain structure, conjugation structure, chromophore conformation, and the protein environment. A prominent bond-stretching mode characteristic of the quinoidal resonance structure is found to be conserved in most FPs and model chromophores investigated, which can be used as a vibrational marker to interpret chromophore-environment interactions and structural effects on the electronic properties of the chromophore. The fundamental insights gained for these light-sensing units (e.g., protein active sites) substantiate the unique and powerful capability of wavelength-tunable FSRS in delineating FP chromophore properties with high sensitivity and resolution in solution and protein matrices. The comprehensive characterization for various FPs across a colorful palette could also serve as a solid foundation for future spectroscopic studies and the rational engineering of FPs with diverse and improved functions.
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Affiliation(s)
- Cheng Chen
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA;
| | - J. Nathan Henderson
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA; (J.N.H.); (J.H.M.)
| | - Dmitry A. Ruchkin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ulitsa Miklukho-Maklaya, 16/10, 117997 Moscow, Russia; (D.A.R.); (M.S.B.); (A.M.B.)
| | - Jacob M. Kirsh
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; (J.M.K.); (S.G.B.)
| | - Mikhail S. Baranov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ulitsa Miklukho-Maklaya, 16/10, 117997 Moscow, Russia; (D.A.R.); (M.S.B.); (A.M.B.)
- Laboratory of Medicinal Substances Chemistry, Institute of Translational Medicine, Pirogov Russian National Research Medical University, Ostrovitianov 1, 117997 Moscow, Russia
| | - Alexey M. Bogdanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ulitsa Miklukho-Maklaya, 16/10, 117997 Moscow, Russia; (D.A.R.); (M.S.B.); (A.M.B.)
| | - Jeremy H. Mills
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA; (J.N.H.); (J.H.M.)
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Steven G. Boxer
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; (J.M.K.); (S.G.B.)
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA;
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36
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Lin YC, Ren P, Webb LJ. AMOEBA Force Field Predicts Accurate Hydrogen Bond Counts of Nitriles in SNase by Revealing Water-Protein Interaction in Vibrational Absorption Frequencies. J Phys Chem B 2023; 127:5609-5619. [PMID: 37339399 PMCID: PMC10851345 DOI: 10.1021/acs.jpcb.3c02060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023]
Abstract
Precisely quantifying the magnitude and direction of electric fields in proteins has long been an outstanding challenge in understanding biological functions. Nitrile vibrational Stark effect probes have been shown to be minimally disruptive to the protein structure and can be better direct reporters of local electrostatic field in the native state of a protein than other measures such as pKa shifts of titratable residues. However, interpretations of the connection between measured vibrational energy and electric field rely on the accurate molecular understanding of interactions of the nitrile group and its environment, particularly from hydrogen bonding. In this work, we compared the extent of hydrogen bonding calculated in two common force fields, the fixed charge force field Amber03 and polarizable force field AMOEBA, at 10 locations of cyanocysteine (CNC) in staphylococcal nuclease (SNase) against the experimental nitrile absorption frequency in terms of full width at half-maximum (FWHM) and frequency temperature line slope (FTLS). We observed that the number of hydrogen bonds correlated well in AMOEBA trajectories with respect to both the FWHM (r = 0.88) and the FTLS (r = -0.85), whereas the correlation of Amber03 trajectories was less reliable because the Amber03 force field predicted more hydrogen bonds in some mutants. Moreover, we demonstrated that contributions from the interactions between CNC and nearby water molecules were significant in AMOEBA trajectories but were not predicted by Amber03. We conclude that although the nitrile absorption peak shape could be qualitatively predicted by the fixed charge Amber03 force field, the detailed electrostatic environment measured by the nitrile probe in terms of the extent of hydrogen bonding could only be accurately observed in the AMOEBA trajectories, where the permanent dipole, quadrupole, and dipole-induced-dipole polarizable interactions were all taken into account. The significance of this finding to the goal of accurately predicting electric fields in complex biomolecular environments is discussed.
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Affiliation(s)
- Yu-Chun Lin
- Department of Chemistry, Texas Materials Institute, and Interdisciplinary Life Sciences Program, The University of Texas at Austin, 105 E 24th St. STOP A5300, Austin, TX, 78712, USA
| | - Pengyu Ren
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Lauren J. Webb
- Department of Chemistry, Texas Materials Institute, and Interdisciplinary Life Sciences Program, The University of Texas at Austin, 105 E 24th St. STOP A5300, Austin, TX, 78712, USA
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37
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Hildebrandt P. Vibrational Spectroscopy of Phytochromes. Biomolecules 2023; 13:1007. [PMID: 37371587 DOI: 10.3390/biom13061007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 06/12/2023] [Accepted: 06/14/2023] [Indexed: 06/29/2023] Open
Abstract
Phytochromes are biological photoswitches that translate light into physiological functions. Spectroscopic techniques are essential tools for molecular research into these photoreceptors. This review is directed at summarizing how resonance Raman and IR spectroscopy contributed to an understanding of the structure, dynamics, and reaction mechanism of phytochromes, outlining the substantial experimental and theoretical challenges and describing the strategies to master them. It is shown that the potential of the various vibrational spectroscopic techniques can be most efficiently exploited using integral approaches via a combination of theoretical methods as well as other experimental techniques.
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Affiliation(s)
- Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin, Sekr. PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany
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38
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Nguyen HM, Morgan HWT, Chantarojsiri T, Kerr TA, Yang JY, Alexandrova AN, Léonard NG. Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes. J Phys Chem A 2023. [PMID: 37316977 DOI: 10.1021/acs.jpca.3c00827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N'-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ε) (acetonitrile, ε = 37.5; N,N-dimethylformamide, ε = 36.7; and dichloromethane, ε = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N'-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field.
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Affiliation(s)
- Hien M Nguyen
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
| | - Harry W T Morgan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Teera Chantarojsiri
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Tyler A Kerr
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
| | - Jenny Y Yang
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
| | - Anastassia N Alexandrova
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Nadia G Léonard
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
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39
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Conti Nibali V, Maiti S, Saija F, Heyden M, Cassone G. Electric-field induced entropic effects in liquid water. J Chem Phys 2023; 158:2889002. [PMID: 37154276 DOI: 10.1063/5.0139460] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 03/13/2023] [Indexed: 05/10/2023] Open
Abstract
Externally applied electric fields in liquid water can induce a plethora of effects with wide implications in electrochemistry and hydrogen-based technologies. Although some effort has been made to elucidate the thermodynamics associated with the application of electric fields in aqueous systems, to the best of our knowledge, field-induced effects on the total and local entropy of bulk water have never been presented so far. Here, we report on classical TIP4P/2005 and ab initio molecular dynamics simulations measuring entropic contributions carried by diverse field intensities in liquid water at room temperature. We find that strong fields are capable of aligning large fractions of molecular dipoles. Nevertheless, the order-maker action of the field leads to quite modest entropy reductions in classical simulations. Albeit more significant variations are recorded during first-principles simulations, the associated entropy modifications are small compared to the entropy change involved in the freezing phenomenon, even at intense fields slightly beneath the molecular dissociation threshold. This finding further corroborates the idea that electrofreezing (i.e., the electric-field-induced crystallization) cannot take place in bulk water at room temperature. In addition, here, we propose a molecular-dynamics-based analysis (3D-2PT) that spatially resolves the local entropy and the number density of bulk water under an electric field, which enables us to map their field-induced changes in the environment of reference H2O molecules. By returning detailed spatial maps of the local order, the proposed approach is capable of establishing a link between entropic and structural modifications with atomistic resolution.
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Affiliation(s)
- Valeria Conti Nibali
- Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University of Messina, 98166 Messina, Italy
- Institute for Chemical-Physical Processes, National Research Council of Italy (IPCF-CNR), 98158 Messina, Italy
| | - Sthitadhi Maiti
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA
| | - Franz Saija
- Institute for Chemical-Physical Processes, National Research Council of Italy (IPCF-CNR), 98158 Messina, Italy
| | - Matthias Heyden
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA
| | - Giuseppe Cassone
- Institute for Chemical-Physical Processes, National Research Council of Italy (IPCF-CNR), 98158 Messina, Italy
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40
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Yan S, Ji X, Peng W, Wang B. Evaluating the Transition State Stabilization/Destabilization Effects of the Electric Fields from Scaffold Residues by a QM/MM Approach. J Phys Chem B 2023; 127:4245-4253. [PMID: 37155960 DOI: 10.1021/acs.jpcb.3c01054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The protein scaffolds of enzymes not only provide structural support for the catalytic center but also exert preorganized electric fields for electrostatic catalysis. In recent years, uniform oriented external electric fields (OEEFs) have been widely applied to enzymatic reactions to mimic the electrostatic effects of the environment. However, the electric fields exerted by individual residues in proteins may be quite heterogeneous across the active site, with varying directions and strengths at different positions of the active site. Here, we propose a QM/MM-based approach to evaluate the effects of the electric fields exerted by individual residues in the protein scaffold. In particular, the heterogeneity of the residue electric fields and the effect of the native protein environment can be properly accounted for by this QM/MM approach. A case study of the O-O heterolysis reaction in the catalytic cycle of TyrH shows that (1) for scaffold residues that are relatively far from the active site, the heterogeneity of the residue electric field in the active site is not very significant and the electrostatic stabilization/destabilization due to each residue can be well approximated with the interaction energy between a uniform electric field and the QM region dipole; (2) for scaffold residues near the active site, the residue electric fields can be highly heterogeneous along the breaking O-O bond. In such a case, approximating the residue electric fields as uniform fields may misrepresent the overall electrostatic effect of the residue. The present QM/MM approach can be applied to evaluate the residues' electrostatic impact on enzymatic reactions, which also can be useful in computational optimization of electric fields to boost the enzyme catalysis.
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Affiliation(s)
- Shengheng Yan
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
| | - Xinwei Ji
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
| | - Wei Peng
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China
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41
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Shi L, Min W. Vibrational Solvatochromism Study of the C-H···O Improper Hydrogen Bond. J Phys Chem B 2023; 127:3798-3805. [PMID: 37122158 DOI: 10.1021/acs.jpcb.2c08119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The improper C-H···O hydrogen bond is an important weak interaction, with broad implications for protein and nucleic acid structure, molecular recognition, enzyme catalysis, and drug interaction. Despite its wide identification in crystal structures, the general existence of C-H···O hydrogen bonds remains elusive especially for natural C-H groups in bulk aqueous solutions at room temperature. Vibrational spectroscopy is a promising methodology to tackle this challenge, as formation of C-H···O hydrogen bonds usually causes shifts of the C-H stretch frequency. Yet, prior observations are inconclusive, as they are all based on a simple blue-shift in aqueous solution and cannot distinguish if it is an effect caused by solvent reorganization or a specific hydrogen-bonding interaction. In this work, we used vibrational solvatochromism as a calibration of the solvent reorganization effect and identified a specific H-bonding interaction. We performed vibrational solvatochromism study of C-H(D) of multiple alcohol molecules including the CH mode of CD3CH(OH)CD3 and the CD3 modes of CD3OH, CD3CH2OH, and CD3CH(OH)CD3 in a series of solvents. We found an abnormal blue-shift of the Raman frequency of the C-H and C-D bonds at both the Cα and Cβ positions of alcohols in water, which lies in an opposite direction to the expected trend due to vibrational solvatochromism. This experimental evidence supports that the improper C-H···O hydrogen bonds might generally exist between nonpolarized C-H and water in liquid solutions at room temperature.
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Affiliation(s)
- Lixue Shi
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Wei Min
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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42
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Wei RJ, Khaniya U, Mao J, Liu J, Batista VS, Gunner MR. Tools for analyzing protonation states and for tracing proton transfer pathways with examples from the Rb. sphaeroides photosynthetic reaction centers. PHOTOSYNTHESIS RESEARCH 2023; 156:101-112. [PMID: 36307598 DOI: 10.1007/s11120-022-00973-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 10/03/2022] [Indexed: 06/16/2023]
Abstract
Protons participate in many reactions. In proteins, protons need paths to move in and out of buried active sites. The vectorial movement of protons coupled to electron transfer reactions establishes the transmembrane electrochemical gradient used for many reactions, including ATP synthesis. Protons move through hydrogen bonded chains of waters and hydroxy side chains via the Grotthuss mechanism and by proton binding and release from acidic and basic residues. MCCE analysis shows that proteins exist in a large number of protonation states. Knowledge of the equilibrium ensemble can provide a rational basis for setting protonation states in simulations that fix them, such as molecular dynamics (MD). The proton path into the QB site in the bacterial reaction centers (RCs) of Rb. sphaeroides is analyzed by MD to provide an example of the benefits of using protonation states found by the MCCE program. A tangled web of side chains and waters link the cytoplasm to QB. MCCE analysis of snapshots from multiple trajectories shows that changing the input protonation state of a residue in MD biases the trajectory shifting the proton affinity of that residue. However, the proton affinity of some residues is more sensitive to the input structure. The proton transfer networks derived from different trajectories are quite robust. There are some changes in connectivity that are largely restricted to the specific residues whose protonation state is changed. Trajectories with QB•- are compared with earlier results obtained with QB [Wei et. al Photosynthesis Research volume 152, pages153-165 (2022)] showing only modest changes. While introducing new methods the study highlights the difficulty of establishing the connections between protein conformation.
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Affiliation(s)
- Rongmei Judy Wei
- Ph.D. Program in Chemistry, The Graduate Center, City University of New York, New York, NY, 10016, USA
- Department of Physics, City College of New York, New York, NY, 10031, USA
| | - Umesh Khaniya
- Department of Physics, City College of New York, New York, NY, 10031, USA
- Ph.D. Program in Physics, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Junjun Mao
- Department of Physics, City College of New York, New York, NY, 10031, USA
| | - Jinchan Liu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, 06520, USA
| | - Victor S Batista
- Department of Chemistry, Yale University, New Haven, CT, 06520, USA
| | - M R Gunner
- Ph.D. Program in Chemistry, The Graduate Center, City University of New York, New York, NY, 10016, USA.
- Department of Physics, City College of New York, New York, NY, 10031, USA.
- Ph.D. Program in Physics, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
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43
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Maitra A, Das P, Thompson BC, Dawlaty JM. Distinguishing between the Electrostatic Effects and Explicit Ion Interactions in a Stark Probe. J Phys Chem B 2023; 127:2511-2520. [PMID: 36917012 DOI: 10.1021/acs.jpcb.2c08030] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
Abstract
Vibrational Stark probes are incisive tools for measuring local electric fields in a wide range of chemical environments. The interpretation of the frequency shift often gets complicated due to the specific interactions of the probe, such as hydrogen bonding and Lewis bonding. Therefore, it is important to distinguish between the pure electrostatic response and the response due to such specific interactions. Here we report a molecular system that is sensitive to both the Stark effect from a single ion and the explicit Lewis bonding of ions with the probe. The molecule consists of a crown ether with an appended benzonitrile. The crown captures cations of various charges, and the electric field from the ions is sensed by the benzonitrile probe. Additionally, the lone pair of the benzonitrile can engage in Lewis interactions with some of the ions by donating partial charge density to the ions. Our system exhibits both of these effects and therefore is a suitable test bed for distinguishing between the pure electrostatic and the Lewis interactions. Our computational results show that the electrostatic influence of the ion is operative at large distances, while the Lewis interaction becomes important only within distances that permit orbital overlap. Our results may be useful for using the nitrile probe for measuring electrostatic and coordination effects in complex ionic environments such as the electrode-electrolyte interfaces.
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Affiliation(s)
- Anwesha Maitra
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Pratyusha Das
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Barry C Thompson
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Jahan M Dawlaty
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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44
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Garrett P, Shirley JC, Baiz CR. Forced Interactions: Ionic Polymers at Charged Surfactant Interfaces. J Phys Chem B 2023; 127:2829-2836. [PMID: 36926899 DOI: 10.1021/acs.jpcb.2c08636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
Characterizing electrostatic interactions at heterogeneous interfaces is critical for developing a fundamental description of the dynamic processes at charged interfaces. Water-in-oil reverse micelles (RMs) offer a high degree of tunability across composition, polarity, and temperature, making them ideal systems for studying interactions at heterogeneous liquid-liquid interfaces. In the present study, we use a combination of ultrafast two-dimensional infrared spectroscopy and molecular dynamics (MD) simulations to determine the picosecond interfacial dynamics in RMs containing binary compositions of sorbitan monostearate and anionic or cationic cosurfactants, which are used to tune the ratio of charged to nonionic surfactants at the interface. The positively charged polyethylenimine (PEI) polymer is encapsulated within the RMs, and the carbonyl stretching mode of sorbitan monostearate reports on the interfacial hydrogen-bond populations and dynamics. The results show that hydrogen-bond populations are altered through the inclusion of both negatively and positively charged cosurfactants. Charged surfactants increase interfacial water penetration into the surfactant layer, and the surface localization of polymers decreases water penetration. Local hydrogen-bond dynamics undergo a slowdown with the inclusion of charged surfactants, and the encapsulation of polymers results in similar effects, irrespective of the charge.
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Affiliation(s)
- Paul Garrett
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Joseph C Shirley
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Carlos R Baiz
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
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45
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Datar A, Wright C, Matthews DA. Theoretical Investigation of the X-ray Stark Effect in Small Molecules. J Phys Chem A 2023; 127:1576-1587. [PMID: 36787229 DOI: 10.1021/acs.jpca.2c08311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
We have studied the Stark effect in the soft x-ray region for various small molecules by calculating the field-dependent x-ray absorption spectra. This effect is explained in terms of the response of molecular orbitals (core and valence), the molecular dipole moment, and the molecular geometry to the applied electric field. A number of consistent trends are observed linking the computed shifts in absorption energies and intensities with specific features of the molecular electronic structure. We find that both the virtual molecular orbitals (valence and/or Rydberg) as well as the core orbitals contribute to observed trends in a complementary fashion. This initial study highlights the potential impact of x-ray Stark spectroscopy as a tool to study electronic structure and environmental perturbations at a submolecular scale.
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Affiliation(s)
- Avdhoot Datar
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
| | - Catherine Wright
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
| | - Devin A Matthews
- Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States
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46
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Chen S, Xiao YH, Qin M, Zhou G, Dong R, Devasenathipathy R, Wu DY, Yang L. Quantification of the Real Plasmonic Field Transverse Distribution in a Nanocavity Using the Vibrational Stark Effect. J Phys Chem Lett 2023; 14:1708-1713. [PMID: 36757268 DOI: 10.1021/acs.jpclett.2c03818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Quantifying the real plasmonic field strength experimentally has been long pursued in expanding the applications related to plasmonic enhancement. However, it is still an enormous challenge to determine the inhomogeneous plasmonic field distribution. Here, self-assembled monolayers (SAMs) of 4-mercaptobenzonitrile (MBN) are sandwiched as a gap spacer in a nanoparticle-on-mirror (NPoM) structure, effectively forming ultrahigh field enhancement to observe Stark shifts of the chemical bond. Transverse position-dependent Stark shifts of ν(C═C) and ν(C≡N) in the individual nanocavity measured by surface-enhanced Raman scattering (SERS) experiment combined with the Stark tuning rate by density functional theory (DFT) simulation accurately revealed the inhomogeneous plasmonic field transverse distribution and quantified the transverse plasmonic field strength up to ∼1.9 × 109 V/m, which matches the value predicted by finite element method (FEM) simulation. This work deepens the insight into plasmon-based technologies and will coordinate high-resolution techniques such as tip-enhanced Raman spectroscopy (TESR) to reveal the real plasmonic field distribution.
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Affiliation(s)
- Siyu Chen
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
- University of Science & Technology of China, Hefei 230026, Anhui, China
| | - Yuan-Hui Xiao
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
| | - Miao Qin
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
| | - Guoliang Zhou
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
- University of Science & Technology of China, Hefei 230026, Anhui, China
| | - Ronglu Dong
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
| | - Rajkumar Devasenathipathy
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
| | - De-Yin Wu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
| | - Liangbao Yang
- Institute of Health and Medical Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, China
- University of Science & Technology of China, Hefei 230026, Anhui, China
- Department of Pharmacy, Hefei Cancer Hospital, Chinese Academy of Sciences, Hefei 230031, Anhui, China
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47
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Aldossary A, Gimferrer M, Mao Y, Hao H, Das AK, Salvador P, Head-Gordon T, Head-Gordon M. Force Decomposition Analysis: A Method to Decompose Intermolecular Forces into Physically Relevant Component Contributions. J Phys Chem A 2023; 127:1760-1774. [PMID: 36753558 DOI: 10.1021/acs.jpca.2c08061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Computational quantum chemistry can be more than just numerical experiments when methods are specifically adapted to investigate chemical concepts. One important example is the development of energy decomposition analysis (EDA) to reveal the physical driving forces behind intermolecular interactions. In EDA, typically the interaction energy from a good-quality density functional theory (DFT) calculation is decomposed into multiple additive components that unveil permanent and induced electrostatics, Pauli repulsion, dispersion, and charge-transfer contributions to noncovalent interactions. Herein, we formulate, implement, and investigate decomposing the forces associated with intermolecular interactions into the same components. The resulting force decomposition analysis (FDA) is potentially useful as a complement to the EDA to understand chemistry, while also providing far more information than an EDA for data analysis purposes such as training physics-based force fields. We apply the FDA based on absolutely localized molecular orbitals (ALMOs) to analyze interactions of water with sodium and chloride ions as well as in the water dimer. We also analyze the forces responsible for geometric changes in carbon dioxide upon adsorption onto (and activation by) gold and silver anions. We also investigate how the force components of an EDA-based force field for water clusters, namely MB-UCB, compare to those from force decomposition analysis.
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Affiliation(s)
- Abdulrahman Aldossary
- Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley California 94720, United States
| | - Martí Gimferrer
- Institut de Química Computacional i Catàlsi and Departament de Química, Universitat de Girona, 17003 Girona, Catalonia Spain
| | - Yuezhi Mao
- Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182, United States
| | - Hongxia Hao
- Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley California 94720, United States
| | - Akshaya K Das
- Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley California 94720, United States
| | - Pedro Salvador
- Institut de Química Computacional i Catàlsi and Departament de Química, Universitat de Girona, 17003 Girona, Catalonia Spain
| | - Teresa Head-Gordon
- Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley California 94720, United States
| | - Martin Head-Gordon
- Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley California 94720, United States
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48
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Islam A, Kikuchi Y, Iimori T. Electroabsorption and Stark Fluorescence Spectroscopies of Thioflavin T. J Phys Chem A 2023; 127:1436-1444. [PMID: 36740807 DOI: 10.1021/acs.jpca.2c07794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Thioflavin T (ThT) is a typical fluorescent marker for detecting the formation of amyloid fibrils, because its fluorescence intensity increases by more than 2 orders of magnitude upon complexation with the fibrils. Strong electrostatic fields on protein surfaces are known to be a significant factor in chemical reactions and biological functions. Therefore, ThT bound to amyloid fibrils must experience strong electric fields. This study employed electroabsorption and Stark fluorescence spectroscopies to clarify the effects of external electric fields on the photophysics of ThT. The absorption spectrum shows two bands ascribed to locally excited (LE) and charge transfer (CT) states. Coupling between the LE and CT states is enhanced in the presence of an external electric field, resulting in fluorescence quenching. The electric field strength of the amyloid fibril surface was inferred from the fluorescence quenching efficiency of ThT.
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Affiliation(s)
- Ahatashamul Islam
- Department of Sciences and Informatics, Muroran Institute of Technology, Mizumoto-cho 27-1, Muroran, Hokkaido050-8585, Japan
| | - Yudai Kikuchi
- Department of Sciences and Informatics, Muroran Institute of Technology, Mizumoto-cho 27-1, Muroran, Hokkaido050-8585, Japan
| | - Toshifumi Iimori
- Department of Sciences and Informatics, Muroran Institute of Technology, Mizumoto-cho 27-1, Muroran, Hokkaido050-8585, Japan
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49
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Wang D, Li W, Dong X, Li H, Hu L. TFRegNCI: Interpretable Noncovalent Interaction Correction Multimodal Based on Transformer Encoder Fusion. J Chem Inf Model 2023; 63:782-793. [PMID: 36652718 DOI: 10.1021/acs.jcim.2c01283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The interpretability is an important issue for end-to-end learning models. Motivated by computer vision algorithms, an interpretable noncovalent interaction (NCI) correction multimodal (TFRegNCI) is proposed for NCI prediction. TFRegNCI is based on RegNet feature extraction and a transformer encoder fusion strategy. RegNet is a network design paradigm that mainly focuses on local features. Meanwhile, the Vision Transformer is also leveraged for feature extraction, because it can capture global features better than RegNet while lowering the computational cost. Using a transformer encoder as the fusion strategy rather than multilayer perceptron can enhance model performance, due to its emphasis on important features with less parameters. Therefore, the proposed TFRegNCI achieved high accurate prediction (mean absolute error of ∼0.1 kcal/mol) comparing with the coupled cluster single double (triple) (CCSD(T)) benchmark. To further improve the model efficiency, TFRegNCI applies two-dimensional (2D) inputs transformed from three-dimensional (3D) electron density cubes, which saves time (30%), while the model accuracy remains. To improve model interpretability, a visualization module, Gradient-weighted Regression Activation Mapping (Grad-RAM) has been embedded. Grad-RAM is promoted from the classification algorithm, Gradient-weighted Class Activation Mapping, to perform feature visualization for the regression task. With Grad-RAM, the visual location map for features in deep learning models can be displayed. The feature map visualizations suggest that the 2D model has the similar performance as the 3D model, because of equally effective feature extractions from electron density. Moreover, the valid feature region on the location map by the 3D model is consistent with the NCIPLOT NCI isosurface. It is confirmed that the model does extract significant features related to the NCI interaction. The interpretable analyses are carried out through molecular orbital contribution on effective features. Thereby, the proposed model is likely to be a promising tool to reveal some essential information on NCIs, with regard to the level of electronic theory.
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Affiliation(s)
- Donghan Wang
- School of Information Science and Technology, Northeast Normal University, Changchun130117, China
| | - Wenze Li
- College of Computer and Information Engineering, Henan Normal University, Henan, Xinxiang453007, China
| | - Xu Dong
- School of Information Science and Technology, Northeast Normal University, Changchun130117, China
| | - Hongzhi Li
- School of Information Science and Technology, Northeast Normal University, Changchun130117, China
| | - LiHong Hu
- School of Information Science and Technology, Northeast Normal University, Changchun130117, China
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50
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Fica-Contreras SM, Charnay AP, Pan J, Fayer MD. Rethinking Vibrational Stark Spectroscopy: Peak Shifts, Line Widths, and the Role of Non-Stark Solvent Coupling. J Phys Chem B 2023; 127:717-731. [PMID: 36629314 DOI: 10.1021/acs.jpcb.2c06071] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A vibration's transition frequency is partly determined by the first-order Stark effect, which accounts for the electric field experienced by the mode. Using ultrafast infrared pump-probe and FT-IR spectroscopies, we characterized both the 0 → 1 and 1 → 2 vibrational transitions' field-dependent peak positions and line widths of the CN stretching mode of benzonitrile (BZN) and phenyl selenocyanate (PhSeCN) in ten solvents. We present a theoretical model that decomposes the observed line width into a field-dependent Stark contribution and a field-independent non-Stark solvent coupling contribution (NSC). The model demonstrates that the field-dependent peak position is independent of the line width, even when the NSC dominates the latter. Experiments show that when the Stark tuning rate is large compared to the NSC (PhSeCN), the line width has a field dependence, albeit with major NSC-induced excursions from linearity. When the Stark tuning rate is small relative to the NSC (BZN), the line width is field-independent. BZN's line widths are substantially larger for the 1 → 2 transition, indicating a 1 → 2 transition enhancement of the NSC. Additionally, we examine, theoretically and experimentally, the difference in the 0 → 1 and 1 → 2 transitions' Stark tuning rates. Second-order perturbation theory combined with density functional theory explain the difference and show that the 1 → 2 transition's Stark tuning rate is ∼10% larger. The Stark tuning rate of PhSeCN is larger than BZN's for both transitions, consistent with the theoretical calculations. This study provides new insights into vibrational line shape components and a more general understanding of the vibrational response to external electric fields.
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Affiliation(s)
| | - Aaron P Charnay
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Junkun Pan
- Department of Chemistry, Stanford University, Stanford, California94305, United States
| | - Michael D Fayer
- Department of Chemistry, Stanford University, Stanford, California94305, United States
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