1
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Ben-Amotz D. Interfacial chemical reactivity enhancement. J Chem Phys 2024; 160:084704. [PMID: 38391019 DOI: 10.1063/5.0186945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 01/16/2024] [Indexed: 02/24/2024] Open
Abstract
Interfacial enhancements of chemical reaction equilibria and rates in liquid droplets are predicted using a combined theoretical and experimental analysis strategy. Self-consistent solutions of reaction and adsorption equilibria indicate that interfacial reactivity enhancement is driven primarily by the adsorption free energy of the product (or activated complex). Reactant surface activity has a smaller indirect influence on reactivity due to compensating reactant interfacial concentration and adsorption free energy changes, as well as adsorption-induced depletion of the droplet core. Experimental air-water interfacial adsorption free energies and critical micelle concentration correlations provide quantitative surface activity estimates as a function of molecular structure, predicting an increase in interfacial reactivity with increasing product size and decreasing product polarity, aromaticity, and charge (but less so for anions than cations). Reactions with small, neutral, or charged products are predicted to have little reactivity enhancement at an air-water interface unless the product is rendered sufficiently surface active by, for example, interactions with interfacial water dangling OH groups, charge transfer, or voltage fluctuations.
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Affiliation(s)
- Dor Ben-Amotz
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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2
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Hashikawa Y, Sadai S, Ikemoto Y, Murata Y. Open-[60]fullerenols with water adsorbed both inside and outside. Chem Commun (Camb) 2024; 60:1261-1264. [PMID: 38180526 DOI: 10.1039/d3cc05542f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
The water affinity on [60]fullerenols was found to be governed by surface electrostatic potential while water aggregation is initiated by the hydroxy groups attached on the carbon surface. The molecular water adsorption at the internal sphere caused a significnat inhibition of water adsorption at the external carbon surface.
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Affiliation(s)
- Yoshifumi Hashikawa
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Shumpei Sadai
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yuka Ikemoto
- Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo 679-5198, Japan
| | - Yasujiro Murata
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
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3
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Raciti D, Cockayne E, Vinson J, Schwarz K, Hight Walker AR, Moffat TP. SHINERS Study of Chloride Order-Disorder Phase Transition and Solvation of Cu(100). J Am Chem Soc 2024; 146:1588-1602. [PMID: 38170994 DOI: 10.1021/jacs.3c11812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) are used to probe Cl- adsorption and the order-disorder phase transition associated with the c(2 × 2) Cl- adlayer on Cu(100) in acid media. A two-component ν(Cu-Cl) vibrational band centered near 260 ± 1 cm-1 is used to track the potential dependence of Cl- adsorption. The potential dependence of the dominant 260 cm-1 component tracks the coverage of the fluctional c(2 × 2) Cl- phase on terraces in good agreement with the normalized intensity of the c(2 × 2) superstructure rods in prior surface X-ray diffraction (SXRD) studies. As the c(2 × 2) Cl- coverage approaches saturation, a second ν(Cu-Cl) component mode emerges between 290 and 300 cm-1 that coincides with the onset and stiffening of step faceting where Cl- occupies the threefold hollow sites to stabilize the metal kink saturated Cu <100> step edge. The formation of the c(2 × 2) Cl- adlayer is accompanied by the strengthening of ν(O-H) stretching modes in the adjacent non-hydrogen-bonded water at 3600 cm-1 and an increase in hydronium concentration evident in the flanking H2O modes at 3100 cm-1. The polarization of the water molecules and enrichment of hydronium arise from the combination of Cl- anionic character and lateral templating provided by the c(2 × 2) adlayer, consistent with SXRD studies. At negative potentials, Cl- desorption occurs followed by development of a sulfate νs(S═O) band. Below -1.1 V vs Hg/HgSO4, a new 200 cm-1 mode emerges congruent with hydride formation and surface reconstruction reported in electrochemical scanning tunneling microscopy studies.
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Affiliation(s)
- David Raciti
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Eric Cockayne
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - John Vinson
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Kathleen Schwarz
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Angela R Hight Walker
- Physical Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Thomas P Moffat
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
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4
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Mouhat F, Peria M, Morresi T, Vuilleumier R, Saitta AM, Casula M. Thermal dependence of the hydrated proton and optimal proton transfer in the protonated water hexamer. Nat Commun 2023; 14:6930. [PMID: 37903819 PMCID: PMC10616126 DOI: 10.1038/s41467-023-42366-4] [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: 12/12/2022] [Accepted: 09/25/2023] [Indexed: 11/01/2023] Open
Abstract
Water is a key ingredient for life and plays a central role as solvent in many biochemical reactions. However, the intrinsically quantum nature of the hydrogen nucleus, revealing itself in a large variety of physical manifestations, including proton transfer, gives rise to unexpected phenomena whose description is still elusive. Here we study, by a combination of state-of-the-art quantum Monte Carlo methods and path-integral molecular dynamics, the structure and hydrogen-bond dynamics of the protonated water hexamer, the fundamental unit for the hydrated proton. We report a remarkably low thermal expansion of the hydrogen bond from zero temperature up to 300 K, owing to the presence of short-Zundel configurations, characterised by proton delocalisation and favoured by the synergy of nuclear quantum effects and thermal activation. The hydrogen bond strength progressively weakens above 300 K, when localised Eigen-like configurations become relevant. Our analysis, supported by the instanton statistics of shuttling protons, reveals that the near-room-temperature range from 250 K to 300 K is optimal for proton transfer in the protonated water hexamer.
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Affiliation(s)
- Félix Mouhat
- Saint Gobain Research Paris, 39, Quai Lucien Lefranc, 93300, Aubervilliers, France
| | - Matteo Peria
- IMPMC, Sorbonne Université, CNRS, MNHN, UMR 7590, 4 Place Jussieu, 75252, Paris, France
| | - Tommaso Morresi
- ECT*-Fondazione Bruno Kessler*, 286 Strada delle Tabarelle, 38123, Trento, Italy
| | - Rodolphe Vuilleumier
- PASTEUR, Département de Chimie, École normale supérieure, PSL Research University, Sorbonne Université, CNRS, 24 Rue Lhomond, 75005, Paris, France
| | - Antonino Marco Saitta
- IMPMC, Sorbonne Université, CNRS, MNHN, UMR 7590, 4 Place Jussieu, 75252, Paris, France
| | - Michele Casula
- IMPMC, Sorbonne Université, CNRS, MNHN, UMR 7590, 4 Place Jussieu, 75252, Paris, France.
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5
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Wang Y, Chen Z, Yang Y. Calculating Vibrational Excited State Absorptions with Excited State Constrained Minimized Energy Surfaces. J Phys Chem A 2023. [PMID: 37335973 DOI: 10.1021/acs.jpca.3c01420] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
The modeling and interpretation of vibrational spectra are crucial for studying reaction dynamics using vibrational spectroscopy. Most prior theoretical developments focused on describing fundamental vibrational transitions while fewer developments focused on vibrational excited state absorptions. In this study, we present a new method that uses excited state constrained minimized energy surfaces (CMESs) to describe vibrational excited state absorptions. The excited state CMESs are obtained similarly to the previous ground state CMES development in our group but with additional wave function orthogonality constraints. Using a series of model systems, including the harmonic oscillator, Morse potential, double-well potential, quartic potential, and two-dimensional anharmonic potential, we demonstrate that this new procedure provides good estimations of the transition frequencies for vibrational excited state absorptions. These results are significantly better than those obtained from harmonic approximations using conventional potential energy surfaces, demonstrating the promise of excited state CMES-based methods for calculating vibrational excited state absorptions in real systems.
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Affiliation(s)
- Yiwen Wang
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin─Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Zehua Chen
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin─Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Yang Yang
- Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin─Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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6
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Wise PK, Slipchenko LV, Ben-Amotz D. Ion-Size Dependent Adsorption Crossover on the Surface of a Water Droplet. J Phys Chem B 2023; 127:4658-4665. [PMID: 37186591 DOI: 10.1021/acs.jpcb.3c01797] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The adsorption of ionic and neutral spherical solutes on the surface of a liquid water droplet are investigated using molecular dynamics simulations and theoretical analyses. The results reveal a crossover in the sign of the adsorption free energy as a function of ion size, with ions larger than iodide predicted to be increasingly surface active. Adsorption free energies are decomposed into competing energetic and entropic contributions arising from direct solute-water interaction energy and its fluctuations. The entropically driven surface activity of large ions is predicted to increase with ion size, while small ions are typically driven away from the interface by a more delicate balance of energetic and entropic contributions, with a nonmonotonic ion size dependence linked to the ion's hydration-shell structure and stability. The physical interpretation of the results is illuminated by comparisons with dielectric linear response and cavity formation predictions and implications to interfacial acidity and enhanced chemical reactivity are discussed.
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Affiliation(s)
- Patrick K Wise
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Lyudmila V Slipchenko
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Dor Ben-Amotz
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
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7
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Brünig FN, Hillmann P, Kim WK, Daldrop JO, Netz RR. Proton-transfer spectroscopy beyond the normal-mode scenario. J Chem Phys 2022; 157:174116. [DOI: 10.1063/5.0116686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A stochastic theory is developed to predict the spectral signature of proton-transfer processes and is applied to infrared spectra computed from ab initio molecular-dynamics simulations of a single [Formula: see text] cation. By constraining the oxygen atoms to a fixed distance, this system serves as a tunable model for general proton-transfer processes with variable barrier height. Three spectral contributions at distinct frequencies are identified and analytically predicted: the quasi-harmonic motion around the most probable configuration, amenable to normal-mode analysis, the contribution due to transfer paths when the proton moves over the barrier, and a shoulder for low frequencies stemming from the stochastic transfer-waiting-time distribution; the latter two contributions are not captured by normal-mode analysis but exclusively reported on the proton-transfer kinetics. In accordance with reaction rate theory, the transfer-waiting-contribution frequency depends inversely exponentially on the barrier height, whereas the transfer-path-contribution frequency is rather insensitive to the barrier height.
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Affiliation(s)
- Florian N. Brünig
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Paul Hillmann
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Won Kyu Kim
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul 02455, Republic of Korea
| | - Jan O. Daldrop
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Roland R. Netz
- Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany
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8
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Tran B, Milner ST, Janik MJ. Kinetics of Acid-Catalyzed Dehydration of Alcohols in Mixed Solvent Modeled by Multiscale DFT/MD. ACS Catal 2022. [DOI: 10.1021/acscatal.2c03978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bolton Tran
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania16802, United States
| | - Scott T. Milner
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania16802, United States
| | - Michael J. Janik
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania16802, United States
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9
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Tran B, Cai Y, Janik MJ, Milner ST. Hydrogen Bond Thermodynamics in Aqueous Acid Solutions: A Combined DFT and Classical Force-Field Approach. J Phys Chem A 2022; 126:7382-7398. [PMID: 36190836 DOI: 10.1021/acs.jpca.2c04124] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The thermodynamics of hydrogen bonds in aqueous and acidic solutions significantly impacts the kinetics and thermodynamics of acid reaction chemistry. We utilize in this work a multiscale approach, combining density functional theory (DFT) with classical molecular dynamics (MD) to model hydrogen bond thermodynamics in an acidic solution. Using thermodynamic cycles, we split the solution phase free energy into its gas phase counterpart plus solvation free energies. We validate this DFT/MD approach by calculating the aqueous phase hydrogen bond free energy between two water molecules (H2O-···-H2O), the free energy to transform an H3O+ cation into an H5O2+ cation, and the hydrogen bond free energy of protonated water clusters (H3O+-···-H2O and H5O2+-···-H2O). The computed equilibrium hydrogen bond free energy of H2O-···-H2O is remarkably accurate, especially considering the large individual contributions to the thermodynamic cycle. Turning to cations, we find the ion to be more stable than H3O+ by roughly 1-2 kBT. This small free energy difference allows for thermal fluctuation between the two idealized motifs, consistent with spectroscopic and simulation studies. Lastly, hydrogen bonding free energies between either H+ cation and H2O in solution were found to be stronger than between two H2O, though much less so than in vacuum because of dielectric screening in solution. Altogether, our results suggest the DFT/MD approach is promising for application in modeling hydrogen bonding and proton transfer thermodynamics in condensed phases.
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Affiliation(s)
- Bolton Tran
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania16801, United States
| | - Yusheng Cai
- Department of Chemical & Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
| | - Michael J Janik
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania16801, United States
| | - Scott T Milner
- Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania16801, United States
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10
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You X, Baiz CR. Importance of Hydrogen Bonding in Crowded Environments: A Physical Chemistry Perspective. J Phys Chem A 2022; 126:5881-5889. [PMID: 35968816 DOI: 10.1021/acs.jpca.2c03803] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cells are heterogeneous on every length and time scale; cytosol contains thousands of proteins, lipids, nucleic acids, and small molecules, and molecular interactions within this crowded environment determine the structure, dynamics, and stability of biomolecules. For decades, the effects of crowding at the atomistic scale have been overlooked in favor of more tractable models largely based on thermodynamics. Crowding can affect the conformations and stability of biomolecules by modulating water structure and dynamics within the cell, and these effects are nonlocal and environment dependent. Thus, characterizing water's hydrogen-bond (H-bond) networks is a critical step toward a complete microscopic crowding model. This perspective provides an overview of molecular crowding and describes recent time-resolved spectroscopy approaches investigating H-bond networks and dynamics in crowded or otherwise complex aqueous environments. Ultrafast spectroscopy combined with atomistic simulations has emerged as a powerful combination for studying H-bond structure and dynamics in heterogeneous multicomponent systems. We discuss the ongoing challenges toward developing a complete atomistic description of macromolecular crowding from an experimental as well as a theoretical perspective.
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Affiliation(s)
- Xiao You
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 19104, United States
| | - Carlos R Baiz
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 19104, United States
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11
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Brünig FN, Rammler M, Adams EM, Havenith M, Netz RR. Spectral signatures of excess-proton waiting and transfer-path dynamics in aqueous hydrochloric acid solutions. Nat Commun 2022; 13:4210. [PMID: 35864099 PMCID: PMC9304333 DOI: 10.1038/s41467-022-31700-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 06/22/2022] [Indexed: 11/23/2022] Open
Abstract
The theoretical basis for linking spectral signatures of hydrated excess protons with microscopic proton-transfer mechanisms has so far relied on normal-mode analysis. We introduce trajectory-decomposition techniques to analyze the excess-proton dynamics in ab initio molecular-dynamics simulations of aqueous hydrochloric-acid solutions beyond the normal-mode scenario. We show that the actual proton transfer between two water molecules involves for relatively large water-water separations crossing of a free-energy barrier and thus is not a normal mode, rather it is characterized by two non-vibrational time scales: Firstly, the broadly distributed waiting time for transfer to occur with a mean value of 200–300 fs, which leads to a broad and weak shoulder in the absorption spectrum around 100 cm−1, consistent with our experimental THz spectra. Secondly, the mean duration of a transfer event of about 14 fs, which produces a rather well-defined spectral contribution around 1200 cm−1 and agrees in location and width with previous experimental mid-infrared spectra. The spectroscopic signatures of excess protons in HCl solutions are studied by ab initio simulations and THz experiments. Two contributions beyond the normal-mode scenario are identified that reflect proton-waiting and proton-transfer processes.
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Affiliation(s)
- Florian N Brünig
- Freie Universität Berlin, Department of Physics, 14195, Berlin, Germany
| | - Manuel Rammler
- Freie Universität Berlin, Department of Physics, 14195, Berlin, Germany
| | - Ellen M Adams
- Ruhr-Universität Bochum, Department of Physical Chemistry II, 44780, Bochum, Germany
| | - Martina Havenith
- Ruhr-Universität Bochum, Department of Physical Chemistry II, 44780, Bochum, Germany
| | - Roland R Netz
- Freie Universität Berlin, Department of Physics, 14195, Berlin, Germany.
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12
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Ikemoto Y, Harada Y, Tanaka M, Nishimura SN, Murakami D, Kurahashi N, Moriwaki T, Yamazoe K, Washizu H, Ishii Y, Torii H. Infrared Spectra and Hydrogen-Bond Configurations of Water Molecules at the Interface of Water-Insoluble Polymers under Humidified Conditions. J Phys Chem B 2022; 126:4143-4151. [PMID: 35639685 PMCID: PMC9189834 DOI: 10.1021/acs.jpcb.2c01702] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Elucidating the state of interfacial water, especially the hydrogen-bond configurations, is considered to be key for a better understanding of the functions of polymers that are exhibited in the presence of water. Here, an analysis in this direction is conducted for two water-insoluble biocompatible polymers, poly(2-methoxyethyl acrylate) and cyclic(poly(2-methoxyethyl acrylate)), and a non-biocompatible polymer, poly(n-butyl acrylate), by measuring their IR spectra under humidified conditions and by carrying out theoretical calculations on model complex systems. It is found that the OH stretching bands of water are decomposed into four components, and while the higher-frequency components (with peaks at ∼3610 and ∼3540 cm-1) behave in parallel with the C═O and C-O-C stretching and CH deformation bands of the polymers, the lower-frequency components (with peaks at ∼3430 and ∼3260 cm-1) become pronounced to a greater extent with increasing humidity. From the theoretical calculations, it is shown that the OH stretching frequency that is distributed from ∼3650 to ∼3200 cm-1 is correlated to the hydrogen-bond configurations and is mainly controlled by the electric field that is sensed by the vibrating H atom. By combining these observed and calculated results, the configurations of water at the interface of the polymers are discussed.
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Affiliation(s)
- Yuka Ikemoto
- Spectroscopy Division, Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Yoshihisa Harada
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.,Synchrotron Radiation Research Organization, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Masaru Tanaka
- Institute for Material Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.,Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Shin-Nosuke Nishimura
- Institute for Material Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Daiki Murakami
- Institute for Material Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.,Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Naoya Kurahashi
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.,Synchrotron Radiation Research Organization, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Taro Moriwaki
- Spectroscopy Division, Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Kosuke Yamazoe
- Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.,Synchrotron Radiation Research Organization, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Hitoshi Washizu
- Graduate School of Information Science, University of Hyogo, 7-1-28 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Yoshiki Ishii
- Graduate School of Information Science, University of Hyogo, 7-1-28 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Hajime Torii
- Department of Applied Chemistry and Biochemical Engineering, Faculty of Engineering, and Department of Optoelectronics and Nanostructure Science, Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan
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13
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Mattio E, Caleyron A, Miguirditchian M, Lines AM, Bryan SA, Lackey HE, Rodriguez-Ruiz I, Lamadie F. Microfluidic In-Situ Spectrophotometric Approaches to Tackle Actinides Analysis in Multiple Oxidation States. APPLIED SPECTROSCOPY 2022; 76:580-589. [PMID: 35108115 DOI: 10.1177/00037028211063916] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The study and development of present and future processes for the treatment/recycling of spent nuclear fuels require many steps, from design in the laboratory to setting up on an industrial scale. In all of these steps, analysis and instrumentation are key points. For scientific reasons (small-scale studies, control of phenomena, etc.) but also with regard to minimizing costs, risks, and waste, such developments are increasingly carried out on milli- or microfluidic devices. The logic is the same for the chemical analyses associated with their follow-up and interpretation. Due to this, over the last few years, opto-microfluidic analysis devices adapted to the monitoring of different processes (dissolution, liquid-liquid extraction, precipitation, etc.) have been increasingly designed and developed. In this work, we prove that photonic lab-on-a-chip (PhLoC) technology is fully suitable for all actinides concentration monitoring along the plutonium uranium refining extraction (plutonium, uranium, reduction, extraction, or Purex) process. Several PhLoC microfluidic platforms were specifically designed and used in different nuclear research and development (R&D) laboratories, to tackle actinides analysis in multiple oxidation states even in mixtures. The detection limits reached (tens of µmol·L-1) are fully compliant with on-line process monitoring, whereas a range of analyzable concentrations of three orders of magnitude can be covered with less than 150 µL of analyte. Finally, this work confirms the possibility and the potential of coupling Raman and ultraviolet-visible (UV-Vis) spectroscopies at the microfluidic scale, opening the perspective of measuring very complex mixtures.
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Affiliation(s)
- Elodie Mattio
- CEA, DES, ISEC, DMRC, 27053Univ Montpellier, Marcoule, France
| | - Audrey Caleyron
- CEA, DES, ISEC, DMRC, 27053Univ Montpellier, Marcoule, France
| | | | - Amanda M Lines
- 6865Pacific Northwest National Laboratory, Richland, WA, USA
| | - Samuel A Bryan
- 6865Pacific Northwest National Laboratory, Richland, WA, USA
| | - Hope E Lackey
- 6865Pacific Northwest National Laboratory, Richland, WA, USA
| | | | - Fabrice Lamadie
- CEA, DES, ISEC, DMRC, 27053Univ Montpellier, Marcoule, France
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14
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Lupi L, Bracco B, Sassi P, Corezzi S, Morresi A, Fioretto D, Comez L, Paolantoni M. Hydration Dynamics of Model Peptides with Different Hydrophobic Character. Life (Basel) 2022; 12:life12040572. [PMID: 35455063 PMCID: PMC9031890 DOI: 10.3390/life12040572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 04/06/2022] [Accepted: 04/08/2022] [Indexed: 11/16/2022] Open
Abstract
The multi-scale dynamics of aqueous solutions of the hydrophilic peptide N-acetyl-glycine-methylamide (NAGMA) have been investigated through extended frequency-range depolarized light scattering (EDLS), which enables the broad-band detection of collective polarizability anisotropy fluctuations. The results have been compared to those obtained for N-acetyl-leucinemethylamide (NALMA), an amphiphilic peptide which shares with NAGMA the same polar backbone, but also contains an apolar group. Our study indicates that the two model peptides induce similar effects on the fast translational dynamics of surrounding water. Both systems slow down the mobility of solvating water molecules by a factor 6–8, with respect to the bulk. Moreover, the two peptides cause a comparable far-reaching spatial perturbation extending to more than two hydration layers in diluted conditions. The observed concentration dependence of the hydration number is explained considering the random superposition of different hydration shells, while no indication of solute aggregation phenomena has been found. The results indicate that the effect on the dynamics of water solvating the amphiphilic peptide is dominated by the hydrophilic backbone. The minor impact of the hydrophobic moiety on hydration features is consistent with structural findings derived by Fourier transform infrared (FTIR) measurements, performed in attenuated total reflectance (ATR) configuration. Additionally, we give evidence that, for both systems, the relaxation mode in the GHz frequency range probed by EDLS is related to solute rotational dynamics. The rotation of NALMA occurs at higher timescales, with respect to the rotation of NAGMA; both processes are significantly slower than the structural dynamics of hydration water, suggesting that solute and solvent motions are uncoupled. Finally, our results do not indicate the presence of super-slow water (relaxation times in the order of tens of picoseconds) around the peptides investigated.
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Affiliation(s)
- Laura Lupi
- Dipartimento di Matematica e Fisica, Università Roma Tre, 00146 Rome, Italy;
| | - Brenda Bracco
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy; (B.B.); (P.S.); (A.M.)
| | - Paola Sassi
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy; (B.B.); (P.S.); (A.M.)
| | - Silvia Corezzi
- Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06123 Perugia, Italy; (S.C.); (D.F.)
| | - Assunta Morresi
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy; (B.B.); (P.S.); (A.M.)
| | - Daniele Fioretto
- Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06123 Perugia, Italy; (S.C.); (D.F.)
- IOM-CNR c/o Department of Physics and Geology, Università degli Studi di Perugia, 060123 Perugia, Italy
| | - Lucia Comez
- IOM-CNR c/o Department of Physics and Geology, Università degli Studi di Perugia, 060123 Perugia, Italy
- Correspondence: (L.C.); (M.P.)
| | - Marco Paolantoni
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy; (B.B.); (P.S.); (A.M.)
- Correspondence: (L.C.); (M.P.)
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15
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Zhang X, Zhou S, Leonik FM, Wang L, Kuroda DG. Quantum mechanical effects in acid–base chemistry. Chem Sci 2022; 13:6998-7006. [PMID: 35774178 PMCID: PMC9200130 DOI: 10.1039/d2sc01784a] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 05/17/2022] [Indexed: 01/04/2023] Open
Abstract
Acid–base chemistry has immense importance for explaining and predicting the chemical products formed by an acid and a base when mixed together. However, the traditional chemistry theories used to describe acid–base reactions do not take into account the effect arising from the quantum mechanical nature of the acidic hydrogen shuttling potential and its dependence on the acid base distance. Here, infrared and NMR spectroscopies, in combination with first principles simulations, are performed to demonstrate that quantum mechanical effects, including electronic and nuclear quantum effects, play an essential role in defining the acid–base chemistry when 1-methylimidazole and acetic acid are mixed together. In particular, it is observed that the acid and the base interact to form a complex containing a strong hydrogen bond, in which the acidic hydrogen atom is neither close to the acid nor to the base, but delocalized between them. In addition, the delocalization of the acidic hydrogen atom in the complex leads to characteristic IR and NMR signatures. The presence of a hydrogen delocalized state in this simple system challenges the conventional knowledge of acid–base chemistry and opens up new avenues for designing materials in which specific properties produced by the hydrogen delocalized state can be harvested. Acid-based theories do not consider the quantum mechanical nature of the acidic hydrogen shuttling potential. Here, it is demonstrated that this particularity is needed to explain the formation acid-base complex with a delocalized acidic hydrogen.![]()
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Affiliation(s)
- Xiaoliu Zhang
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Shengmin Zhou
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Fedra M. Leonik
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Lu Wang
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Daniel G. Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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16
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Silverstein TP. The Proton in Biochemistry: Impacts on Bioenergetics, Biophysical Chemistry, and Bioorganic Chemistry. Front Mol Biosci 2021; 8:764099. [PMID: 34901158 PMCID: PMC8661011 DOI: 10.3389/fmolb.2021.764099] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/11/2021] [Indexed: 11/13/2022] Open
Abstract
The proton is the smallest atomic particle, and in aqueous solution it is the smallest hydrated ion, having only two waters in its first hydration shell. In this article we survey key aspects of the proton in chemistry and biochemistry, starting with the definitions of pH and pK a and their application inside biological cells. This includes an exploration of pH in nanoscale spaces, distinguishing between bulk and interfacial phases. We survey the Eigen and Zundel models of the structure of the hydrated proton, and how these can be used to explain: a) the behavior of protons at the water-hydrophobic interface, and b) the extraordinarily high mobility of protons in bulk water via Grotthuss hopping, and inside proteins via proton wires. Lastly, we survey key aspects of the effect of proton concentration and proton transfer on biochemical reactions including ligand binding and enzyme catalysis, as well as pH effects on biochemical thermodynamics, including the Chemiosmotic Theory. We find, for example, that the spontaneity of ATP hydrolysis at pH ≥ 7 is not due to any inherent property of ATP (or ADP or phosphate), but rather to the low concentration of H+. Additionally, we show that acidification due to fermentation does not derive from the organic acid waste products, but rather from the proton produced by ATP hydrolysis.
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Affiliation(s)
- Todd P Silverstein
- Chemistry Department (emeritus), Willamette University, Salem, OR, United States
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17
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Cui X, Tang M, Wang M, Zhu T. Water as a probe for pH measurement in individual particles using micro-Raman spectroscopy. Anal Chim Acta 2021; 1186:339089. [PMID: 34756261 DOI: 10.1016/j.aca.2021.339089] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 09/16/2021] [Accepted: 09/20/2021] [Indexed: 10/20/2022]
Abstract
Atmospheric aerosol acidity impacts numerous physicochemical processes, but the determination of particle pH remains a significant challenge due to the nonconservative nature of the H+ concentration ([H+]). Traditional measurements have difficulty in describing the practical state of an aerosol because they comprise chemical components or hypotheses that change the nature of the particles. In this work, we present a direct pH measurement that uses water as a general probe to detect [H+] in individual particles by micro-Raman spectroscopy. Containing the vibrational bands of ions and water influenced by ions, the spectra of hydrated ion were decomposed from the solution spectra as standard spectra by multivariate curve resolution analysis. Meanwhile, ratios of hydrated ions were calculated between the Raman spectra and standard spectra to evaluate concentration profiles of each ion. It demonstrated that good quantitative models between the ratio and concentration for all ions including H+ can be built with correlation coefficients (R2) higher than 0.95 for the solutions. The method was further applied to individual particle pH measurement. The pH value of sulfate aerosol particles was calculated, and the standard error was 0.09 using pH values calculated from the [HSO4-]/[SO42-] as a reference. Furthermore, the applicability of the method was proven by detecting the pH value of chloride particles. Therefore, utilizing water, the most common substance, as the spectroscopic probe to measure [H+] without restriction of the ion system, this method has potential to measure the pH value of atmospheric particles with various compounds, although more work needs to be done to improve the sensitivity of the method.
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Affiliation(s)
- Xiaoyu Cui
- BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
| | - Mingjin Tang
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
| | - Mingjin Wang
- BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
| | - Tong Zhu
- BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
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18
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Calio PB, Li C, Voth GA. Resolving the Structural Debate for the Hydrated Excess Proton in Water. J Am Chem Soc 2021; 143:18672-18683. [PMID: 34723507 DOI: 10.1021/jacs.1c08552] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
It has long been proposed that the hydrated excess proton in water (aka the solvated "hydronium" cation) likely has two limiting forms, that of the Eigen cation (H9O4+) and that of the Zundel cation (H5O2+). There has been debate over which of these two is the more dominant species and/or whether intermediate (or "distorted") structures between these two limits are the more realistic representation. Spectroscopy experiments have recently provided further results regarding the excess proton. These experiments show that the hydrated proton has an anisotropy reorientation time scale on the order of 1-2 ps. This time scale has been suggested to possibly contradict the picture of the more rapid "special pair dance" phenomenon for the hydrated excess proton, which is a signature of a distorted Eigen cation. The special pair dance was predicted from prior computational studies in which the hydrated central core hydronium structure continually switches (O-H···O)* special pair hydrogen-bond partners with the closest three water molecules, yielding on average a distorted Eigen cation with three equivalent and dynamically exchanging distortions. Through state-of-art simulations it is shown here that anisotropy reorientation time scales of the same magnitude are obtained that also include structural reorientations associated with the special pair dance, leading to a reinterpretation of the experimental results. These results and additional analyses point to a distorted and dynamic Eigen cation as the most prevalent hydrated proton species in aqueous acid solutions of dilute to moderate concentration, as opposed to a stabilized or a distorted (but not "dancing") Zundel cation.
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Affiliation(s)
- Paul B Calio
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Chenghan Li
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
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19
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Hanson MD, Readnour JA, Hassanali AA, Corcelli SA. Coupled Local-Mode Approach for the Calculation of Vibrational Spectra: Application to Protonated Water Clusters. J Phys Chem Lett 2021; 12:9226-9232. [PMID: 34529914 DOI: 10.1021/acs.jpclett.1c02254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Spectroscopic studies of protonated water clusters (PWCs) have yielded enormous insights into the fundamental nature of the hydrated proton. Here, we introduce a new coupled local-mode (CLM) approach to calculate PWC OH stretch vibrational spectra. The CLM method combines a sampling of representative configurations from density functional theory (DFT)-based ab initio molecular dynamics (AIMD) simulations with DFT calculations of local-mode vibrational frequencies and couplings. Calculations of inhomogeneous OH stretch vibrational spectra for H+(H2O)4 and H+(H2O)21 agree well with experiment and higher-level calculations, and decompositions of the calculated spectra in terms of the coupled modes aids in the interpretation of the spectra. This observation is consistent with the idea that capturing anharmonicity and coupling is as important to accuracy as the underlying level of electronic structure theory. The CLM calculations can easily discern the configuration that dominates the experimental measurement for H+(H2O)5, which can adopt several low-energy conformations.
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Affiliation(s)
- Matthew D Hanson
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Janel A Readnour
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Ali A Hassanali
- Condensed Matter and Statistical Physics, International Centre for Theoretical Physics, Strada Costiera, 11 I - 34151 Trieste, Italy
| | - Steven A Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
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20
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Corezzi S, Bracco B, Sassi P, Paolantoni M, Comez L. Protein Hydration in a Bioprotecting Mixture. Life (Basel) 2021; 11:life11100995. [PMID: 34685367 PMCID: PMC8537178 DOI: 10.3390/life11100995] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/10/2021] [Accepted: 09/18/2021] [Indexed: 11/16/2022] Open
Abstract
We combined broad-band depolarized light scattering and infrared spectroscopies to study the properties of hydration water in a lysozyme-trehalose aqueous solution, where trehalose is present above the concentration threshold (30% in weight) relevant for biopreservation. The joint use of the two different techniques, which were sensitive to inter-and intra-molecular degrees of freedom, shed new light on the molecular mechanism underlying the interaction between the three species in the mixture. Thanks to the comparison with the binary solution cases, we were able to show that, under the investigated conditions, the protein, through preferential hydration, remains strongly hydrated even in the ternary mixture. This supported the water entrapment scenario, for which a certain amount of water between protein and sugar protects the biomolecule from damage caused by external agents.
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Affiliation(s)
- Silvia Corezzi
- Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06123 Perugia, Italy;
| | - Brenda Bracco
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy; (B.B.); (P.S.)
| | - Paola Sassi
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy; (B.B.); (P.S.)
| | - Marco Paolantoni
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy; (B.B.); (P.S.)
- Correspondence: (M.P.); (L.C.)
| | - Lucia Comez
- CNR-IOM at Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06123 Perugia, Italy
- Correspondence: (M.P.); (L.C.)
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21
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Biswas B, Singh PC. Signature of the surface hydrated proton and associated restructuring of water at model membrane interfaces: a vibrational sum frequency generation study. Phys Chem Chem Phys 2021; 23:14764-14769. [PMID: 34196339 DOI: 10.1039/d1cp01486b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrated proton at membrane interfaces plays an important role in the bioenergetic process of almost all organisms. Herein, the signature of the hydrated proton at membrane interfaces has been investigated by measuring the vibrational sum frequency generated (VSFG) spectra of negatively charged and zwitterionic lipids in the presence of different concentrations of acids. The addition of acids decreases the intensity of the OH stretch of the VSFG signal of water present at the negatively charged and zwitterionic lipids along with the enhanced intensity of the broad VSFG signal in the range of 2500-2800 cm-1. The enhanced intensity of the broad continuum observed in the range of 2500-2800 cm-1 has been assigned to the signature of the hydrated proton at the lipid interfaces. The decrease in the VSFG signal of the OH stretch of water along with the appearance of the broad signal suggests that the hydrated proton exists in the vicinity of the lipid interfaces and restructures the interaction between the interfacial water molecules.
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Affiliation(s)
- Biswajit Biswas
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India.
| | - Prashant Chandra Singh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India.
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22
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Arntsen C, Chen C, Calio PB, Li C, Voth GA. The hopping mechanism of the hydrated excess proton and its contribution to proton diffusion in water. J Chem Phys 2021; 154:194506. [PMID: 34240917 DOI: 10.1063/5.0040758] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In this work, a series of analyses are performed on ab initio molecular dynamics simulations of a hydrated excess proton in water to quantify the relative occurrence of concerted hopping events and "rattling" events and thus to further elucidate the hopping mechanism of proton transport in water. Contrary to results reported in certain earlier papers, the new analysis finds that concerted hopping events do occur in all simulations but that the majority of events are the product of proton rattling, where the excess proton will rattle between two or more waters. The results are consistent with the proposed "special-pair dance" model of the hydrated excess proton wherein the acceptor water molecule for the proton transfer will quickly change (resonate between three equivalent special pairs) until a decisive proton hop occurs. To remove the misleading effect of simple rattling, a filter was applied to the trajectory such that hopping events that were followed by back hops to the original water are not counted. A steep reduction in the number of multiple hopping events is found when the filter is applied, suggesting that many multiple hopping events that occur in the unfiltered trajectory are largely the product of rattling, contrary to prior suggestions. Comparing the continuous correlation function of the filtered and unfiltered trajectories, we find agreement with experimental values for the proton hopping time and Eigen-Zundel interconversion time, respectively.
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Affiliation(s)
- Christopher Arntsen
- Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA
| | - Chen Chen
- Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Paul B Calio
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Chenghan Li
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
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23
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de Oliveira DM, Bredt AJ, Miller TC, Corcelli SA, Ben-Amotz D. Spectroscopic and Structural Characterization of Water-Shared Ion-Pairs in Aqueous Sodium and Lithium Hydroxide. J Phys Chem B 2021; 125:1439-1446. [PMID: 33512171 DOI: 10.1021/acs.jpcb.0c10564] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Aria J. Bredt
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Tierney C. Miller
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Steven A. Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Dor Ben-Amotz
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
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24
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Cassone G. Nuclear Quantum Effects Largely Influence Molecular Dissociation and Proton Transfer in Liquid Water under an Electric Field. J Phys Chem Lett 2020; 11:8983-8988. [PMID: 33035059 DOI: 10.1021/acs.jpclett.0c02581] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Proton transfer in liquid water controls acid-base chemistry, crucial enzyme reactions, and the functioning of fuel cells. Externally applied static electric fields in water are capable of dissociating molecules and transferring protons across the H-bond network. However, the impact of nuclear quantum effects (NQEs) on these fundamental field-induced phenomena has not yet been reported. By comparing state-of-the-art ab initio molecular dynamics (AIMD) and path integral AIMD simulations of water under electric fields, I show that quantum delocalization of the proton lowers the molecular ionization threshold to approximately one-third. Moreover, also the water behavior as a protonic semiconductor is considerably modified by the inclusion of NQEs. In fact, when the quantum nature of the nuclei is taken into account, the proton conductivity is ∼50% larger. This work proves that NQEs sizably affect the protolysis phenomenon and proton transfer in room-temperature liquid water.
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Affiliation(s)
- Giuseppe Cassone
- Institute for Chemical-Physical Processes, National Research Council, Viale F. Stagno d'Alcontres 37, 98158 Messina, Italy
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25
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Calio PB, Li C, Voth GA. Molecular Origins of the Barriers to Proton Transport in Acidic Aqueous Solutions. J Phys Chem B 2020; 124:8868-8876. [PMID: 32924490 DOI: 10.1021/acs.jpcb.0c06223] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The self-consistent iterative multistate empirical valence bond (SCI-MS-EVB) method is used to analyze the structure, thermodynamics, and dynamics of hydrochloric acid solutions. The reorientation time scales of irreversible proton transport are elucidated by simulating 0.43, 0.85, 1.68, and 3.26 M HCl solutions at 270, 285, 300, 315, and 330 K. The results indicate increased counterion pairing with increasing concentration, which manifests itself via a reduced hydronium oxygen-chloride (O*-Cl) structuring in the radial distribution functions. Increasing ionic concentration also reduces the diffusion of the hydrated excess protons, principally by reducing the contribution of the Grotthuss proton hopping (shuttling) mechanism to the overall diffusion process. In agreement with prior experimental findings, a decrease in the activation energy of reorientation time scales was also observed, which is explicitly explained by using activated rate theory and an energy-entropy decomposition of the state-averaged radial distribution functions. These results provide atomistic verification of suggestions from recent two-dimensional infrared spectroscopy experiments that chloride anions (as opposed to hydrated excess protons) create entropic barriers to proton transport.
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Affiliation(s)
- Paul B Calio
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Chenghan Li
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
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26
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Carpenter WB, Yu Q, Hack JH, Dereka B, Bowman JM, Tokmakoff A. Decoding the 2D IR spectrum of the aqueous proton with high-level VSCF/VCI calculations. J Chem Phys 2020; 153:124506. [PMID: 33003749 DOI: 10.1063/5.0020279] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The aqueous proton is a common and long-studied species in chemistry, yet there is currently intense interest devoted to understanding its hydration structure and transport dynamics. Typically described in terms of two limiting structures observed in gas-phase clusters, the Zundel H5O2 + and Eigen H9O4 + ions, the aqueous structure is less clear due to the heterogeneity of hydrogen bonding environments and room-temperature structural fluctuations in water. The linear infrared (IR) spectrum, which reports on structural configurations, is challenging to interpret because it appears as a continuum of absorption, and the underlying vibrational modes are strongly anharmonically coupled to each other. Recent two-dimensional IR (2D IR) experiments presented strong evidence for asymmetric Zundel-like motifs in solution, but true structure-spectrum correlations are missing and complicated by the anharmonicity of the system. In this study, we employ high-level vibrational self-consistent field/virtual state configuration interaction calculations to demonstrate that the 2D IR spectrum reports on a broad distribution of geometric configurations of the aqueous proton. We find that the diagonal 2D IR spectrum around 1200 cm-1 is dominated by the proton stretch vibrations of Zundel-like and intermediate geometries, broadened by the heterogeneity of aqueous configurations. There is a wide distribution of multidimensional potential shapes for the proton stretching vibration with varying degrees of potential asymmetry and confinement. Finally, we find specific cross peak patterns due to aqueous Zundel-like species. These studies provide clarity on highly debated spectral assignments and stringent spectroscopic benchmarks for future simulations.
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Affiliation(s)
- William B Carpenter
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Qi Yu
- Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA
| | - John H Hack
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Bogdan Dereka
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Joel M Bowman
- Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
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27
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Cota R, van Dam EP, Woutersen S, Bakker HJ. Slowing Down of the Molecular Reorientation of Water in Concentrated Alkaline Solutions. J Phys Chem B 2020; 124:8309-8316. [PMID: 32841025 PMCID: PMC7520889 DOI: 10.1021/acs.jpcb.0c03614] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It is generally accepted that the hydroxide ion (OH-) is a strong hydrogen bond acceptor and that its anomalously high diffusion constant in water results from a Grotthuss-like structural diffusion mechanism. However, the spatial extent over which OH- ions influence the dynamics of the hydrogen-bond network of water remained largely unclear. Here, we measure the ultrafast dynamics of OH groups of HDO molecules interacting with the deuterated hydroxide ion OD-. For solutions with OD- concentrations up to 4 M, we find that HDO molecules that are not directly interacting with the ions have a reorientation time constant of ∼2.7 ps, similar to that of pure liquid water. When the concentration of OD- ions is increased, the reorientation time constant increases, indicating a strong slowing down of the structural dynamics of the solution.
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Affiliation(s)
- Roberto Cota
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands.,AMOLF, Science Park 104, 1098 XG Amsterdam, Netherlands
| | | | - Sander Woutersen
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
| | - Huib J Bakker
- AMOLF, Science Park 104, 1098 XG Amsterdam, Netherlands
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28
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Malm C, Prädel LA, Marekha BA, Grechko M, Hunger J. Composition-Dependent Hydrogen-Bonding Motifs and Dynamics in Brønsted Acid-Base Mixtures. J Phys Chem B 2020; 124:7229-7238. [PMID: 32701282 PMCID: PMC7443859 DOI: 10.1021/acs.jpcb.0c04714] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
In
recent years the interaction of organophosphates and imines,
which is at the core of Brønsted acid organocatalysis, has been
established to be based on strong ionic hydrogen bonds. Yet, besides
the formation of homodimers consisting of two acid molecules and heterodimers
consisting of one acid and one base, also multimeric molecular aggregates
are formed in solution. These multimeric aggregates consist of one
base and several acid molecules. The details of the intermolecular
bonding in such aggregates, however, have remained elusive. To characterize
composition-dependent bonding and bonding dynamics in these aggregates,
we use linear and nonlinear infrared (IR) spectroscopy at varying
molar ratios of diphenyl phosphoric acid and quinaldine. We identify
the individual aggregate species, giving rise to the structured, strong,
and very broad infrared absorptions, which span more than 1000 cm–1. Linear infrared spectra and density functional theory
calculations of the proton transfer potential show that doubly ionic
intermolecular hydrogen bonds between the acid and the base lead to
absorptions which peak at ∼2040 cm–1. The
contribution of singly ionic hydrogen bonds between an acid anion
and an acid molecule is observed at higher frequencies. As common
to such strong hydrogen bonds, ultrafast IR spectroscopy reveals rapid,
∼ 100 fs, dissipation of energy from the proton transfer coordinate.
Yet, the full dissipation of the excess energy occurs on a ∼0.8–1.1
ps time scale, which becomes longer when multimers dominate. Our results
thus demonstrate the coupling and collectivity of the hydrogen bonds
within these complexes, which enable efficient energy transfer.
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Affiliation(s)
- Christian Malm
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Leon A Prädel
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Bogdan A Marekha
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Maksim Grechko
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Johannes Hunger
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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29
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Sofronov O, Bakker HJ. Slow Proton Transfer in Nanoconfined Water. ACS CENTRAL SCIENCE 2020; 6:1150-1158. [PMID: 32724849 PMCID: PMC7379388 DOI: 10.1021/acscentsci.0c00340] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Indexed: 06/11/2023]
Abstract
The transport of protons in nanoconfined environments, such as in nanochannels of biological or artificial proton conductive membranes, is essential to chemistry, biology, and nanotechnology. In water, proton diffusion occurs by hopping of protons between water molecules. This process involves the rearrangement of many hydrogen bonds and as such can be strongly affected by nanoconfinement. We study the vibrational and structural dynamics of hydrated protons in water nanodroplets stabilized by a cationic surfactant using polarization-resolved femtosecond infrared transient absorption spectroscopy. We determine the time scale of proton hopping in the center of the water nanodroplets from the dynamics of the anisotropy of the transient absorption signals. We find that in small nanodroplets with a diameter <4 nm, proton hopping is more than 10 times slower than in bulk water. Even in relatively large nanodroplets with a diameter of ∼7 nm, we find that the rate of proton hopping is slowed by ∼4 times compared with bulk water.
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30
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Cracchiolo OM, Geremia DK, Corcelli SA, Serrano AL. Hydrogen Bond Exchange and Ca2+ Binding of Aqueous N-Methylacetamide Revealed by 2DIR Spectroscopy. J Phys Chem B 2020; 124:6947-6954. [DOI: 10.1021/acs.jpcb.0c02444] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Olivia M. Cracchiolo
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Danielle K. Geremia
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Steven A. Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Arnaldo L. Serrano
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
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31
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Li C, Swanson JMJ. Understanding and Tracking the Excess Proton in Ab Initio Simulations; Insights from IR Spectra. J Phys Chem B 2020; 124:5696-5708. [PMID: 32515957 PMCID: PMC7448536 DOI: 10.1021/acs.jpcb.0c03615] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Proton transport in aqueous media is ubiquitously important in chemical and biological processes. Although ab initio molecular dynamics (AIMD) simulations have made great progress in characterizing proton transport, there has been a long-standing challenge in defining and tracking the excess proton, or more properly, the center of excess charge (CEC) created when a hydrogen nucleus distorts the electron distributions of water molecules in a delocalized and highly dynamic nature. Yet, defining (and biasing) such a CEC is essential when combining AIMD with enhanced sampling methods to calculate the relevant macroscopic properties via free-energy landscapes, which is the standard practice for most processes of interest. Several CEC formulas have been proposed and used, but none have yet been systematically tested or rigorously derived. In this paper, we show that the CEC can be used as a computational tool to disentangle IR features of the solvated excess proton from its surrounding solvent, and in turn, how correlating the features in the excess charge spectrum with the behavior of CEC in simulations enables a systematic evaluation of various CEC definitions. We present a new definition of CEC and show how it overcomes the limitations of those currently available both from a spectroscopic point of view and from a practical perspective of performance in enhanced sampling simulations.
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Affiliation(s)
- Chenghan Li
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Jessica M. J. Swanson
- Department of Chemistry, Biological Chemistry Program, and Center for Cell and Genome Science, The University of Utah, Salt Lake City, Utah 84112, United States
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32
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Roy S, Schenter GK, Napoli JA, Baer MD, Markland TE, Mundy CJ. Resolving Heterogeneous Dynamics of Excess Protons in Aqueous Solution with Rate Theory. J Phys Chem B 2020; 124:5665-5675. [DOI: 10.1021/acs.jpcb.0c02649] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Santanu Roy
- Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37830, United States
| | - Gregory K. Schenter
- Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99352, United States
| | - Joseph A. Napoli
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305, United States
| | - Marcel D. Baer
- Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99352, United States
| | - Thomas E. Markland
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305, United States
| | - Christopher J. Mundy
- Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, Washington 99352, United States
- Affiliate Professor, Department of Chemical Engineering, University of Washington, Seattle, United States
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33
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Tyrode E, Sengupta S, Sthoer A. Identifying Eigen-like hydrated protons at negatively charged interfaces. Nat Commun 2020; 11:493. [PMID: 31980619 PMCID: PMC6981112 DOI: 10.1038/s41467-020-14370-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 01/06/2020] [Indexed: 11/24/2022] Open
Abstract
Despite the importance of the hydrogen ion in a wide range of biological, chemical, and physical processes, its molecular structure in solution remains lively debated. Progress has been primarily hampered by the extreme diffuse nature of the vibrational signatures of hydrated protons in bulk solution. Using the inherently surface-specific vibrational sum frequency spectroscopy technique, we show that at selected negatively charged interfaces, a resolved spectral feature directly linked to the H3O+ core in an Eigen-like species can be readily identified in a biologically compatible pH range. Centered at ~2540 cm−1, the band is seen to shift to ~1875 cm−1 when forming D3O+ upon isotopic substitution. The results offer the possibility of tracking and understanding from a molecular perspective the behavior of hydrated protons at charged interfaces. Hydrated protons are always present in aqueous solution, but their molecular structure remains under debate. Here the authors use vibrational sum frequency spectroscopy to show that at negatively charged liquid–vapor interfaces, protons adopt a specific configuration characteristic of Eigen-like species.
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Affiliation(s)
- Eric Tyrode
- Department of Chemistry, KTH Royal Institute of Technology, SE-10044, Stockholm, Sweden.
| | - Sanghamitra Sengupta
- Department of Chemistry, KTH Royal Institute of Technology, SE-10044, Stockholm, Sweden
| | - Adrien Sthoer
- Department of Chemistry, KTH Royal Institute of Technology, SE-10044, Stockholm, Sweden
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34
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Das S, Imoto S, Sun S, Nagata Y, Backus EHG, Bonn M. Nature of Excess Hydrated Proton at the Water-Air Interface. J Am Chem Soc 2020; 142:945-952. [PMID: 31867949 PMCID: PMC6966913 DOI: 10.1021/jacs.9b10807] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Indexed: 01/02/2023]
Abstract
Understanding the interfacial molecular structure of acidic aqueous solutions is important in the context of, e.g., atmospheric chemistry, biophysics, and electrochemistry. The hydration of the interfacial proton is necessarily different from that in the bulk, given the lower effective density of water at the interface, but has not yet been elucidated. Here, using surface-specific vibrational spectroscopy, we probe the response of interfacial protons at the water-air interface and reveal the interfacial proton continuum. Combined with spectral calculations based on ab initio molecular dynamics simulations, the proton at the water-air interface is shown to be well-hydrated, despite the limited availability of hydration water, with both Eigen and Zundel structures coexisting at the interface. Notwithstanding the interfacial hydrated proton exhibiting bulk-like structures, a substantial interfacial stabilization by -1.3 ± 0.2 kcal/mol is observed experimentally, in good agreement with our free energy calculations. The surface propensity of the proton can be attributed to the interaction between the hydrated proton and its counterion.
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Affiliation(s)
- Sudipta Das
- Department
for Molecular Spectroscopy, Max Planck Institute
for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Sho Imoto
- Department
for Molecular Spectroscopy, Max Planck Institute
for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Shumei Sun
- Department
for Molecular Spectroscopy, Max Planck Institute
for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Department
of Physical Chemistry, University of Vienna, Währinger Strasse 42, 1090 Vienna, Austria
| | - Yuki Nagata
- Department
for Molecular Spectroscopy, Max Planck Institute
for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Ellen H. G. Backus
- Department
for Molecular Spectroscopy, Max Planck Institute
for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Department
of Physical Chemistry, University of Vienna, Währinger Strasse 42, 1090 Vienna, Austria
| | - Mischa Bonn
- Department
for Molecular Spectroscopy, Max Planck Institute
for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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35
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Multistate Reactive Molecular Dynamics Simulations of Proton Diffusion in Water Clusters and in the Bulk. J Phys Chem B 2019; 123:9846-9861. [PMID: 31647873 DOI: 10.1021/acs.jpcb.9b03258] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The molecular mechanics with proton transfer (MMPT) force field is combined with multistate adiabatic reactive molecular dynamics (MS-ARMD) to describe proton transport in the condensed phase. Parametrization for small protonated water clusters based on electronic structure calculations at the MP2/6-311+G(2d,2p) level of theory and refinement by comparing with infrared spectra for a protonated water tetramer yields a force field which faithfully describes the minimum energy structures of small protonated water clusters. In protonated water clusters up to (H2O)100H+, the proton hopping rate is around 100 hops/ns. This rate converges for 21 ≤ n ≤ 31, and no further speedup in bulk water is found. This indicates that bulklike behavior requires the solvation of a Zundel motif by ∼25 water molecules, which corresponds to the second solvation sphere. For smaller cluster sizes, the number of available states (i.e., the number of proton acceptors) is too small and slows down proton-transfer rates. The cluster simulations confirm that the excess proton is typically located on the surface. The free-energy surface as a function of the weights of the two lowest states and a configurational parameter suggests that the "special pair" plays a central role in rapid proton transport. The barriers between this minimum-energy structure and the Zundel and Eigen minima are sufficiently low (∼1 kcal/mol, consistent with recent experiments and commensurate with a hopping rate of ∼100/ns or 1 every 10 ps), leading to a highly dynamic environment. These findings are also consistent with recent experiments which find that Zundel-type hydration geometries are prevalent in bulk water.
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36
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Baumler SM, Hartt V WH, Allen HC. Hydration of ferric chloride and nitrate in aqueous solutions: water-mediated ion pairing revealed by Raman spectroscopy. Phys Chem Chem Phys 2019; 21:19172-19180. [PMID: 31433403 DOI: 10.1039/c9cp01392j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Iron is the most abundant transition metal in the earth's crust and is important for the proper functioning of many technological and natural processes. Despite the importance, a complete microscopic understanding of the hydration of ferric ions and water mediated ion pairing has not been realized. Hydrated Fe(iii) is difficult to study due to the process of complexation to the anion and hydrolysis of the hydrating water molecules leading to a heterogeneous solution with diverse speciation. Here, ferric chloride and nitrate aqueous solutions are studied using polarized Raman spectroscopy as a function of concentration and referenced to their respective sodium salt or mineral acid. Perturbed water spectra (PWS) were generated using multivariate curve resolution-alternating least squares (MCR-ALS) to show the residual spectral response uniquely attributable to the hydration of ferric speciation. The hydrogen bonding network associated with the hydrating water molecules in ferric chloride solutions are found to be more similar to hydrochloric acid solutions, whereas in ferric nitrate solutions, the network behaves more similar to sodium nitrate, despite increased acidity. Thus, in the FeNO3 and FeCl3 solutions, ion pairing and coordination, respectively, are significantly influencing the hydration spectra signature. These results further reveal concentration dependent changes to the hydrogen bonding network, hydrating water symmetry, and changes to the relative abundance of solvent shared ion pairs that are governed primarily by the ferric salt identity.
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Affiliation(s)
- Stephen M Baumler
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
| | - William H Hartt V
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
| | - Heather C Allen
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
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37
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Wexler AD, Fuchs EC, Woisetschläger J, Vitiello G. Electrically induced liquid-liquid phase transition in water at room temperature. Phys Chem Chem Phys 2019; 21:18541-18550. [PMID: 31397450 DOI: 10.1039/c9cp03192h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In this work we expand on findings previously reported [Wexler et al., Phys. Chem. Chem. Phys., 2016, 18, 16281] on the experimental observation of a phase transition in a hydrogen bonded liquid manifesting in long range dipole-dipole interactions. The studied system, liquid water stressed by an electric field, exhibits collective oscillations brought about through spontaneous breakdown of symmetry. Raman spectroscopy identifies the primary excitation of the emergent phase as transverse optically active phonon-like sidebands that appear on the hydrogen bonded asymmetric stretch mode. The phase transition is observed throughout the entire volume of liquid. The system also exhibits a self-similarity relation between the scattered Raman intensity and the electric field strength which further supports the conclusion that collective behavior persists against thermal disruption. The experimental findings are discussed in terms of a quantum field theory for macroscopic quantum systems.
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Affiliation(s)
- Adam D Wexler
- Arie Zwijnenburg Laboratory for Advanced Microscopy and Optical Metrology, Wetsus - European Center of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA Leeuwarden, The Netherlands.
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38
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Yu Q, Carpenter WB, Lewis NHC, Tokmakoff A, Bowman JM. High-Level VSCF/VCI Calculations Decode the Vibrational Spectrum of the Aqueous Proton. J Phys Chem B 2019; 123:7214-7224. [PMID: 31361141 DOI: 10.1021/acs.jpcb.9b05723] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The hydrated excess proton is a common species in aqueous chemistry, which complexes with water in a variety of structures. The infrared spectrum of the aqueous proton is particularly sensitive to this array of structures, which manifests as continuous IR absorption from 1000 to 3000 cm-1 known as the "proton continuum". Because of the extreme breadth of the continuum and strong anharmonicity of the involved vibrational modes, this spectrum has eluded straightforward interpretation and simulation. Using protonated water hexamer clusters from reactive molecular dynamics trajectories, and focusing on their central H+(H2O)2 structures' spectral contribution, we reproduce the linear IR spectrum of the aqueous proton with a high-level local monomer quantum method and highly accurate many-body potential energy surface. The accuracy of this approach is first verified in the vibrational spectra of the two isomers of the protonated water hexamer in the gas phase. We then apply this approach to 800 H+(H2O)6 clusters, also written as [H+(H2O)2](H2O)4, drawn from multistate empirical valence bond simulations of the bulk liquid to calculate the infrared spectrum of the aqueous proton complex. Incorporation of anharmonic effects to the vibrational potential and quantum mechanical treatment of the proton produces a better agreement to the infrared spectrum compared to that of the double-harmonic approximation. We assess the correlation of the proton stretching mode with different atomistic coordinates, finding the best correlation with ⟨ROH⟩, the expectation value of the proton-oxygen distance ROH. We also decompose the IR spectrum based on normal mode vibrations and ⟨ROH⟩ to provide insight on how different frequency regions in the continuum report on different configurations, vibrational modes, and mode couplings.
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Affiliation(s)
- Qi Yu
- Department of Chemistry and Cherry L. Emerson Center for Scientific Computation , Emory University , Atlanta , Georgia 30322 , United States
| | - William B Carpenter
- Department of Chemistry, James Frank Institute, and Institute for Biophysical Dynamics , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Nicholas H C Lewis
- Department of Chemistry, James Frank Institute, and Institute for Biophysical Dynamics , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Andrei Tokmakoff
- Department of Chemistry, James Frank Institute, and Institute for Biophysical Dynamics , The University of Chicago , Chicago , Illinois 60637 , United States
| | - Joel M Bowman
- Department of Chemistry and Cherry L. Emerson Center for Scientific Computation , Emory University , Atlanta , Georgia 30322 , United States
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39
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Egan CK, Paesani F. Assessing Many-Body Effects of Water Self-Ions. II: H3O+(H2O)n Clusters. J Chem Theory Comput 2019; 15:4816-4833. [DOI: 10.1021/acs.jctc.9b00418] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Colin K. Egan
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
| | - Francesco Paesani
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States
- Materials Science and Engineering, University of California San Diego, La Jolla, California 92093, United States
- San Diego Supercomputer Center, University of California San Diego, La Jolla, California 92093, United States
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40
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Yuan R, Napoli JA, Yan C, Marsalek O, Markland TE, Fayer MD. Tracking Aqueous Proton Transfer by Two-Dimensional Infrared Spectroscopy and ab Initio Molecular Dynamics Simulations. ACS CENTRAL SCIENCE 2019; 5:1269-1277. [PMID: 31403075 PMCID: PMC6661862 DOI: 10.1021/acscentsci.9b00447] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Indexed: 05/26/2023]
Abstract
Proton transfer in water is ubiquitous and a critical elementary event that, via proton hopping between water molecules, enables protons to diffuse much faster than other ions. The problem of the anomalous nature of proton transport in water was first identified by Grotthuss over 200 years ago. In spite of a vast amount of modern research effort, there are still many unanswered questions about proton transport in water. An experimental determination of the proton hopping time has remained elusive due to its ultrafast nature and the lack of direct experimental observables. Here, we use two-dimensional infrared spectroscopy to extract the chemical exchange rates between hydronium and water in acid solutions using a vibrational probe, methyl thiocyanate. Ab initio molecular dynamics (AIMD) simulations demonstrate that the chemical exchange is dominated by proton hopping. The observed experimental and simulated acid concentration dependence then allow us to extrapolate the measured single step proton hopping time to the dilute limit, which, within error, gives the same value as inferred from measurements of the proton mobility and NMR line width analysis. In addition to obtaining the proton hopping time in the dilute limit from direct measurements and AIMD simulations, the results indicate that proton hopping in dilute acid solutions is induced by the concerted multi-water molecule hydrogen bond rearrangement that occurs in pure water. This proposition on the dynamics that drive proton hopping is confirmed by a combination of experimental results from the literature.
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Affiliation(s)
- Rongfeng Yuan
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Joseph A. Napoli
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Chang Yan
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Ondrej Marsalek
- Charles
University, Faculty of Mathematics and Physics, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - Thomas E. Markland
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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41
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Carpenter WB, Lewis NHC, Fournier JA, Tokmakoff A. Entropic barriers in the kinetics of aqueous proton transfer. J Chem Phys 2019; 151:034501. [PMID: 31325917 DOI: 10.1063/1.5108907] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Aqueous proton transport is uniquely rapid among aqueous processes, mediated by fluctuating hydrogen bond reorganization in liquid water. In a process known as Grotthuss diffusion, the excess charge diffuses primarily by sequential proton transfers between water molecules rather than standard Brownian motion, which explains the anomalously high electrical conductivity of acidic solutions. Employing ultrafast IR spectroscopy, we use the orientational anisotropy decay of the bending vibrations of the hydrated proton complex to study the picosecond aqueous proton transfer kinetics as a function of temperature, concentration, and counterion. We find that the orientational anisotropy decay exhibits Arrhenius behavior, with an apparent activation energy of 2.4 kcal/mol in 1M and 2M HCl. Interestingly, acidic solutions at high concentration with longer proton transfer time scales display corresponding decreases in activation energy. We interpret this counterintuitive trend by considering the entropic and enthalpic contributions to the activation free energy for proton transfer. Halide counteranions at high concentrations impose entropic barriers to proton transfer in the form of constraints on the solution's collective H-bond fluctuations and obstruction of potential proton transfer pathways. The corresponding proton transfer barrier decreases due to weaker water-halide H-bonds in close proximity to the excess proton, but the entropic effects dominate and result in a net reduction in the proton transfer rate. We estimate the activation free energy for proton transfer as ∼1.0 kcal/mol at 280 K.
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Affiliation(s)
- William B Carpenter
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Nicholas H C Lewis
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Joseph A Fournier
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA
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42
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Abstract
Hydration-shell vibrational spectroscopy provides an experimental window into solute-induced water structure changes that mediate aqueous folding, binding, and self-assembly. Decomposition of measured Raman and infrared (IR) spectra of aqueous solutions using multivariate curve resolution (MCR) and related methods may be used to obtain solute-correlated spectra revealing solute-induced perturbations of water structure, such as changes in water hydrogen-bond strength, tetrahedral order, and the presence of dangling (non-hydrogen-bonded) OH groups. More generally, vibrational-MCR may be applied to both aqueous and nonaqueous solutions, including multicomponent mixtures, to quantify solvent-mediated interactions between oily, polar, and ionic solutes, in both dilute and crowded fluids. Combining vibrational-MCR with emerging theoretical modeling strategies promises synergetic advances in the predictive understanding of multiscale self-assembly processes of both biological and technological interest.
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Affiliation(s)
- Dor Ben-Amotz
- Department of Chemistry , Purdue University , West Lafayette , Indiana 47907 , United States
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43
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Fischer SA, Gunlycke D. Analysis of Correlated Dynamics in the Grotthuss Mechanism of Proton Diffusion. J Phys Chem B 2019; 123:5536-5544. [DOI: 10.1021/acs.jpcb.9b02610] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Sean A. Fischer
- Chemistry Division, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Daniel Gunlycke
- Chemistry Division, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States
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44
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Kananenka AA, Hestand NJ, Skinner JL. OH-Stretch Raman Multivariate Curve Resolution Spectroscopy of HOD/H2O Mixtures. J Phys Chem B 2019; 123:5139-5146. [DOI: 10.1021/acs.jpcb.9b02686] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alexei A. Kananenka
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
| | - Nicholas J. Hestand
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
| | - J. L. Skinner
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
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45
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Kundu A, Dahms F, Fingerhut BP, Nibbering ETJ, Pines E, Elsaesser T. Hydrated Excess Protons in Acetonitrile/Water Mixtures: Solvation Species and Ultrafast Proton Motions. J Phys Chem Lett 2019; 10:2287-2294. [PMID: 30999753 DOI: 10.1021/acs.jpclett.9b00756] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The solvation structure of protons in aqueous media is highly relevant to electric properties and to proton transport in liquids and membranes. At ambient temperature, polar liquids display structural fluctuations on femto- to picosecond time scales with a direct impact on proton solvation. We use two-dimensional infrared (2D-IR) spectroscopy to follow proton dynamics in acetonitrile/water mixtures with the Zundel cation H5O2+ prepared in neat acetonitrile as a benchmark. The 2D-IR spectra of the proton transfer mode of H5O2+ demonstrate stochastic large-amplitude motions in the double-minimum proton potential, driven by fluctuating electric fields. In all cases, the excess proton is embedded in a water dimer, forming an H5O2+ complex as the major solvation species. This observation is rationalized by quantum mechanics/molecular mechanics molecular dynamics simulations including up to four water molecules embedded in acetonitrile. The Zundel motif interacts with its closest water neighbor in an H7O3+ unit without persistent proton localization.
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Affiliation(s)
- Achintya Kundu
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie , Berlin 12489 , Germany
| | - Fabian Dahms
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie , Berlin 12489 , Germany
| | - Benjamin P Fingerhut
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie , Berlin 12489 , Germany
| | - Erik T J Nibbering
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie , Berlin 12489 , Germany
| | - Ehud Pines
- Department of Chemistry , Ben Gurion University of the Negev , Beer-Sheva 84105 , Israel
| | - Thomas Elsaesser
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie , Berlin 12489 , Germany
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46
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Drexler CI, Miller TC, Rogers BA, Li YC, Daly CA, Yang T, Corcelli SA, Cremer PS. Counter Cations Affect Transport in Aqueous Hydroxide Solutions with Ion Specificity. J Am Chem Soc 2019; 141:6930-6936. [DOI: 10.1021/jacs.8b13458] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
| | - Tierney C. Miller
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | | | | | - Clyde A. Daly
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | | | - Steven A. Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
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Lewis NHC, Fournier JA, Carpenter WB, Tokmakoff A. Direct Observation of Ion Pairing in Aqueous Nitric Acid Using 2D Infrared Spectroscopy. J Phys Chem B 2018; 123:225-238. [DOI: 10.1021/acs.jpcb.8b10019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Nicholas H. C. Lewis
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Joseph A. Fournier
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - William B. Carpenter
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
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Sengupta S, Moberg DR, Paesani F, Tyrode E. Neat Water-Vapor Interface: Proton Continuum and the Nonresonant Background. J Phys Chem Lett 2018; 9:6744-6749. [PMID: 30407831 DOI: 10.1021/acs.jpclett.8b03069] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Whether the surface of neat water is "acidic" or "basic" remains an active and controversial field of research. Most of the experimental evidence supporting the preferential adsorption of H3O+ ions stems from nonlinear optical spectroscopy methods typically carried out at extreme pH conditions (pH < 1). Here, we use vibrational sum frequency spectroscopy (VSFS) to target the "proton continuum", an unexplored frequency range characteristic of hydrated protons and hydroxide ions. The VSFS spectra of neat water show a broad and nonzero signal intensity between 1700 and 3000 cm-1 in the three different polarization combinations examined. By comparing the SF response of water with that from dilute HCl and NaOH aqueous solutions, we conclude the intensity does not originate from either adsorbed H3O+ or OH- ions. Contributions from the nonresonant background are then critically considered by comparing the experimental results with many-body molecular dynamics (MB-MD) simulated spectra.
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Affiliation(s)
- Sanghamitra Sengupta
- Department of Chemistry , KTH Royal Institute of Technology , SE-10044 Stockholm , Sweden
| | | | | | - Eric Tyrode
- Department of Chemistry , KTH Royal Institute of Technology , SE-10044 Stockholm , Sweden
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Kundu A, Dahms F, Fingerhut BP, Nibbering ET, Pines E, Elsaesser T. Ultrafast vibrational relaxation and energy dissipation of hydrated excess protons in polar solvents. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2018.10.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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50
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Sofronov OO, Bakker HJ. Energy Relaxation and Structural Dynamics of Protons in Water/DMSO Mixtures. J Phys Chem B 2018; 122:10005-10013. [PMID: 30351147 PMCID: PMC6216113 DOI: 10.1021/acs.jpcb.8b06938] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
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We
investigate the structure and dynamics of proton solvation structures
in mixed water/dimethyl sulfoxide (DMSO) solvents using two-color
mid-infrared femtosecond pump–probe spectroscopy. At a water
fraction below 20%, protons are mainly solvated as (DMSO-H)+ and (DMSO-H)+-H2O structures. We find that
excitation of the OH-stretch vibration of the proton in (DMSO-H)+-H2O structures leads to an ultrafast contraction
of the hydrogen bond between (DMSO-H)+ and H2O. This excited state relaxes rapidly with T1 = 95 ± 10 fs and leads in part to a strong local heating
effect and in part to predissociation of the protonated cluster into
(DMSO-H)+ and water monomers.
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Affiliation(s)
| | - Huib J Bakker
- AMOLF , Science Park 104 , 1098 XG Amsterdam , The Netherlands
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