1
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Choudhury A, Santra S, Ghosh D. Understanding the Photoprocesses in Biological Systems: Need for Accurate Multireference Treatment. J Chem Theory Comput 2024; 20:4951-4964. [PMID: 38864715 DOI: 10.1021/acs.jctc.4c00027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2024]
Abstract
Light-matter interaction is crucial to life itself and revolves around many of the central processes in biology. The need for understanding these photochemical and photophysical processes cannot be overemphasized. Interaction of light with biological systems starts with the absorption of light and subsequent phenomena that occur in the excited states of the system. However, excited states are typically difficult to understand within the mean field approximation of quantum chemical methods. Therefore, suitable multireference methods and methodologies have been developed to understand these phenomena. In this Perspective, we will describe a few methods and methodologies suitable for these descriptions and discuss some persisting difficulties.
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Affiliation(s)
- Arpan Choudhury
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Supriyo Santra
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Debashree Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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2
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Di Prima D, Reinholdt P, Kongsted J. Color Tuning in Bovine Rhodopsin through Polarizable Embedding. J Phys Chem B 2024. [PMID: 38489248 DOI: 10.1021/acs.jpcb.3c07891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2024]
Abstract
Bovine rhodopsin is among the most studied proteins in the rhodopsin family. Its primary activation mechanism is the photoisomerization of 11-cis retinal, triggered by the absorption of a UV-visible photon. Different mutants of the same rhodopsin show different absorption wavelengths due to the influence of the specific amino acid residues forming the cavity in which the retinal chromophore is embedded, and rhodopsins activated at different wavelengths are, for example, exploited in the field of optogenetics. In this letter, we present a procedure for systematically investigating color tuning in models of bovine rhodopsin and a set of its mutants embedded in a membrane bilayer. Vertical excitation energy calculations were carried out with the polarizable embedding potential for describing the environment surrounding the chromophore. We show that polarizable embedding outperformed regular electrostatic embedding in determining both the vertical excitation energies and associated oscillator strengths of the systems studied.
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Affiliation(s)
- Duccio Di Prima
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M DK-5230, Denmark
| | - Peter Reinholdt
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M DK-5230, Denmark
| | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense M DK-5230, Denmark
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3
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Reboredo FA, Kent PRC, Krogel JT. Evaluation of the excitation spectra with diffusion Monte Carlo on an auxiliary bosonic ground state. J Chem Phys 2023; 159:114118. [PMID: 37724730 DOI: 10.1063/5.0155513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 08/29/2023] [Indexed: 09/21/2023] Open
Abstract
We aim to improve upon the variational Monte Carlo (VMC) approach for excitations replacing the Jastrow factor by an auxiliary bosonic (AB) ground state and multiplying it by a fermionic component factor. The instantaneous change in imaginary time of an arbitrary excitation in the original interacting fermionic system is obtained by measuring observables via the ground-state distribution of walkers of an AB system that is subject to an auxiliary effective potential. The effective potential is used to (i) drive the AB system's ground-state configuration space toward the configuration space of the excitations of the original fermionic system and (ii) subtract from a diffusion Monte Carlo (DMC) calculation contributions that can be included in conventional approximations, such as mean-field and configuration interaction (CI) methods. In this novel approach, the AB ground state is treated statistically in DMC, whereas the fermionic component of the original system is expanded in a basis. The excitation energies of the fermionic eigenstates are obtained by sampling a fermion-boson coupling term on the AB ground state. We show that this approach can take advantage of and correct for approximate eigenstates obtained via mean-field calculations or truncated interactions. We demonstrate that the AB ground-state factor incorporates the correlations missed by standard Jastrow factors, further reducing basis truncation errors. Relevant parts of the theory have been tested in soluble model systems and exhibit excellent agreement with exact analytical data and CI and VMC approaches. In particular, for limited basis set expansions and sufficient statistics, AB approaches outperform CI and VMC in terms of basis size for the same systems. The implementation of this method in current codes, despite being demanding, will be facilitated by reusing procedures already developed for calculating ground-state properties with DMC and excitations with VMC.
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Affiliation(s)
- Fernando A Reboredo
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Paul R C Kent
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Jaron T Krogel
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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4
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Raghavan B, Paulikat M, Ahmad K, Callea L, Rizzi A, Ippoliti E, Mandelli D, Bonati L, De Vivo M, Carloni P. Drug Design in the Exascale Era: A Perspective from Massively Parallel QM/MM Simulations. J Chem Inf Model 2023. [PMID: 37319347 DOI: 10.1021/acs.jcim.3c00557] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The initial phases of drug discovery - in silico drug design - could benefit from first principle Quantum Mechanics/Molecular Mechanics (QM/MM) molecular dynamics (MD) simulations in explicit solvent, yet many applications are currently limited by the short time scales that this approach can cover. Developing scalable first principle QM/MM MD interfaces fully exploiting current exascale machines - so far an unmet and crucial goal - will help overcome this problem, opening the way to the study of the thermodynamics and kinetics of ligand binding to protein with first principle accuracy. Here, taking two relevant case studies involving the interactions of ligands with rather large enzymes, we showcase the use of our recently developed massively scalable Multiscale Modeling in Computational Chemistry (MiMiC) QM/MM framework (currently using DFT to describe the QM region) to investigate reactions and ligand binding in enzymes of pharmacological relevance. We also demonstrate for the first time strong scaling of MiMiC-QM/MM MD simulations with parallel efficiency of ∼70% up to >80,000 cores. Thus, among many others, the MiMiC interface represents a promising candidate toward exascale applications by combining machine learning with statistical mechanics based algorithms tailored for exascale supercomputers.
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Affiliation(s)
- Bharath Raghavan
- Computational Biomedicine, Institute of Advanced Simulations IAS-5/Institute for Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
- Department of Physics, RWTH Aachen University, Aachen 52074, Germany
| | - Mirko Paulikat
- Computational Biomedicine, Institute of Advanced Simulations IAS-5/Institute for Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
| | - Katya Ahmad
- Computational Biomedicine, Institute of Advanced Simulations IAS-5/Institute for Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
| | - Lara Callea
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza 1, 20126 Milan, Italy
| | - Andrea Rizzi
- Computational Biomedicine, Institute of Advanced Simulations IAS-5/Institute for Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
- Atomistic Simulations, Italian Institute of Technology, Genova 16163, Italy
| | - Emiliano Ippoliti
- Computational Biomedicine, Institute of Advanced Simulations IAS-5/Institute for Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
| | - Davide Mandelli
- Computational Biomedicine, Institute of Advanced Simulations IAS-5/Institute for Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
| | - Laura Bonati
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza 1, 20126 Milan, Italy
| | - Marco De Vivo
- Molecular Modelling and Drug Discovery, Italian Institute of Technology, Genova 16163, Italy
| | - Paolo Carloni
- Computational Biomedicine, Institute of Advanced Simulations IAS-5/Institute for Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich 52428, Germany
- Department of Physics and Universitätsklinikum, RWTH Aachen University, Aachen 52074, Germany
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5
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Wan X, Zhang Z, Wang A, Su J, Zhou W, Robertson J, Peng Y, Zheng Y, Guo Y. Deep-learning-assisted theoretical insights into the compatibility of environment friendly insulation medium with metal surface of power equipment. J Colloid Interface Sci 2023; 648:317-326. [PMID: 37301156 DOI: 10.1016/j.jcis.2023.05.188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 05/05/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023]
Abstract
Exploring a new generation of eco-friendly gas insulation medium to replace greenhouse gas sulphur hexafluoride (SF6) in power industry is significant for reducing the greenhouse effect and building a low-carbon environment. The gas-solid compatibility of insulation gas with various electrical equipment is also of significance before practical applications. Herein, take a promising SF6 replacing gas trifluoromethyl sulfonyl fluoride (CF3SO2F) for example, one strategy to theoretically evaluate the gas-solid compatibility between insulation gas and the typical solid surfaces of common equipment was raised. Firstly, the active site where the CF3SO2F molecule is prone to interact with other compounds was identified. Secondly, the interaction strength and charge transfer between CF3SO2F and four typical solid surfaces of equipment were studied by first-principles calculations and further analysis was conducted, with SF6 as the control group. Then, the dynamic compatibility of CF3SO2F with solid surfaces was investigated by large-scale molecular dynamics simulations with the aid of deep learning. The results indicate that CF3SO2F has excellent compatibility similar to SF6, especially in the equipment whose contact surface is Cu, CuO, and Al2O3 due to their similar outermost orbital electronic structures. Besides, the dynamic compatibility with pure Al surfaces is poor. Finally, preliminary experimental verifications indicate the validity of the strategy.
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Affiliation(s)
- Xuhao Wan
- School of Electrical Engineering and Automation, Wuhan University, Wuhan, Hubei 430072, China; Department of Engineering, Cambridge University, Cambridge CB2 1PZ, United Kingdom
| | - Zhaofu Zhang
- The Institute of Technological Sciences, Wuhan University, Wuhan, Hubei 430072, China
| | - Anyang Wang
- School of Electrical Engineering and Automation, Wuhan University, Wuhan, Hubei 430072, China
| | - Jinhao Su
- School of Electrical Engineering and Automation, Wuhan University, Wuhan, Hubei 430072, China
| | - Wenjun Zhou
- School of Electrical Engineering and Automation, Wuhan University, Wuhan, Hubei 430072, China
| | - John Robertson
- Department of Engineering, Cambridge University, Cambridge CB2 1PZ, United Kingdom
| | - Yuan Peng
- China Electronics Technology Group Taiji Corporation, Beijing 100846, China
| | - Yu Zheng
- School of Electrical Engineering and Automation, Wuhan University, Wuhan, Hubei 430072, China.
| | - Yuzheng Guo
- School of Electrical Engineering and Automation, Wuhan University, Wuhan, Hubei 430072, China.
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6
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Otis L, Neuscamman E. A promising intersection of excited‐state‐specific methods from quantum chemistry and quantum Monte Carlo. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2023. [DOI: 10.1002/wcms.1659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Affiliation(s)
- Leon Otis
- Department of Physics University of California Berkeley Berkeley California USA
| | - Eric Neuscamman
- Department of Chemistry University of California Berkeley Berkeley California USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley California USA
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7
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Shepard S, Panadés-Barrueta RL, Moroni S, Scemama A, Filippi C. Double Excitation Energies from Quantum Monte Carlo Using State-Specific Energy Optimization. J Chem Theory Comput 2022; 18:6722-6731. [DOI: 10.1021/acs.jctc.2c00769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Stuart Shepard
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
| | | | - Saverio Moroni
- CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali and SISSA Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, I-34136 Trieste, Italy
| | - Anthony Scemama
- Laboratoire de Chimie et Physique Quantiques, Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Claudia Filippi
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands
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8
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Pedraza-González L, Barneschi L, Padula D, De Vico L, Olivucci M. Evolution of the Automatic Rhodopsin Modeling (ARM) Protocol. Top Curr Chem (Cham) 2022; 380:21. [PMID: 35291019 PMCID: PMC8924150 DOI: 10.1007/s41061-022-00374-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 01/29/2022] [Indexed: 10/27/2022]
Abstract
In recent years, photoactive proteins such as rhodopsins have become a common target for cutting-edge research in the field of optogenetics. Alongside wet-lab research, computational methods are also developing rapidly to provide the necessary tools to analyze and rationalize experimental results and, most of all, drive the design of novel systems. The Automatic Rhodopsin Modeling (ARM) protocol is focused on providing exactly the necessary computational tools to study rhodopsins, those being either natural or resulting from mutations. The code has evolved along the years to finally provide results that are reproducible by any user, accurate and reliable so as to replicate experimental trends. Furthermore, the code is efficient in terms of necessary computing resources and time, and scalable in terms of both number of concurrent calculations as well as features. In this review, we will show how the code underlying ARM achieved each of these properties.
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Affiliation(s)
- Laura Pedraza-González
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro 2, 53100, Siena, Italy. .,Department of Chemistry and Industrial Chemistry, University of Pisa, Via Moruzzi 13, 56124, Pisa, Italy.
| | - Leonardo Barneschi
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro 2, 53100, Siena, Italy
| | - Daniele Padula
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro 2, 53100, Siena, Italy
| | - Luca De Vico
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro 2, 53100, Siena, Italy.
| | - Massimo Olivucci
- Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro 2, 53100, Siena, Italy. .,Department of Chemistry, Bowling Green State University, Bowling Green, OH, 43403, USA.
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9
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Lu SY, Zuehlsdorff TJ, Hong H, Aguirre VP, Isborn CM, Shi L. The Influence of Electronic Polarization on Nonlinear Optical Spectroscopy. J Phys Chem B 2021; 125:12214-12227. [PMID: 34726915 DOI: 10.1021/acs.jpcb.1c05914] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The environment surrounding a chromophore can dramatically affect the energy absorption and relaxation process, as manifested in optical spectra. Simulations of nonlinear optical spectroscopy, such as two-dimensional electronic spectroscopy (2DES) and transient absorption (TA), will be influenced by the computational model of the environment. We here compare a fixed point charge molecular mechanics model and a quantum mechanical (QM) model of the environment in computed 2DES and TA spectra of Nile red in water and the chromophore of photoactive yellow protein (PYP) in water and protein environments. In addition to simulating these nonlinear optical spectra, we directly juxtapose the computed excitation energy correlation function to the dynamic Stokes shift function often used to analyze environment dynamics. Overall, we find that for the three systems studied here the mutual electronic polarization provided by the QM environment manifests in broader 2DES signals, as well as a larger reorganization energy and a larger static Stokes shift due to stronger coupling between the chromophore and the environment.
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Affiliation(s)
- Shao-Yu Lu
- Department of Chemistry and Biochemistry, University of California Merced, Merced, California 95343, United States
| | - Tim J Zuehlsdorff
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | - Hanbo Hong
- Department of Chemistry and Biochemistry, University of California Merced, Merced, California 95343, United States
| | - Vincent P Aguirre
- Department of Chemistry and Biochemistry, University of California Merced, Merced, California 95343, United States
| | - Christine M Isborn
- Department of Chemistry and Biochemistry, University of California Merced, Merced, California 95343, United States
| | - Liang Shi
- Department of Chemistry and Biochemistry, University of California Merced, Merced, California 95343, United States
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10
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Scholz L, Neugebauer J. Protein Response Effects on Cofactor Excitation Energies from First Principles: Augmenting Subsystem Time-Dependent Density-Functional Theory with Many-Body Expansion Techniques. J Chem Theory Comput 2021; 17:6105-6121. [PMID: 34524815 DOI: 10.1021/acs.jctc.1c00551] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We investigate the possibility of describing protein response effects on a chromophore excitation by means of subsystem time-dependent density-functional theory (sTDDFT) in combination with a many-body expansion (MBE) approach. While sTDDFT is in principle intrinsically able to include such contributions, addressing cofactor excitations in protein models or entire proteins with full environment-response treatments is currently out of reach. Taking different model structures of the green fluorescent protein (GFP) and bovine rhodopsin as examples, we demonstrate that an embedded-MBE approach based on sTDDFT in its simplest version leads to a good agreement of the predicted protein response effect already at second order. To reproduce reference response effects from nonsubsystem TDDFT calculations quantitatively (error ≤ 5%), however, a third- or even fourth-order MBE may be required. For the latter case, we explore a selective inclusion of fourth-order terms that drastically reduces the computational burden. In addition, we demonstrate how this sTDDFT-MBE treatment can be utilized as an analysis tool to identify residues with dominant response contributions. This, in turn, can be employed to arrive at smaller structural models for light-absorbing proteins, which still feature all of the main characteristics in terms of photoresponse properties.
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Affiliation(s)
- Linus Scholz
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Johannes Neugebauer
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
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11
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Adam S, Wiebeler C, Schapiro I. Structural Factors Determining the Absorption Spectrum of Channelrhodopsins: A Case Study of the Chimera C1C2. J Chem Theory Comput 2021; 17:6302-6313. [PMID: 34255519 DOI: 10.1021/acs.jctc.1c00160] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Channelrhodopsins are photosensitive proteins that trigger flagella motion in single-cell algae and have been successfully utilized in optogenetic applications. In optogenetics, light is used to activate neural cells in living organisms, which can be achieved by exploiting the ion channel signaling of channelrhodopsins. Tailoring channelrhodopsins for such applications includes the tuning of the absorption maximum. In order to establish rational design and to obtain a desired spectral shift, a basic understanding of the absorption spectrum is required. We have studied the chimera C1C2 as a representative of this protein family and the first member with an available crystal structure. For this purpose, we sampled the conformations of C1C2 using quantum mechanical/molecular mechanical molecular dynamics and subjected the resulting snapshots of the trajectory to excitation energy calculations using ADC(2) and simplified time-dependent density functional theory. In contrast to previous reports, we found that different hydrogen-bonding networks-involving the retinal protonated Schiff base, the putative counterions E162 and D292, and water molecules-had only a small impact on the absorption spectrum. However, in the case of deprotonated E162, increasing the distance to the Schiff base hydrogen-bonding partner led to a systematic blue shift. The β-ionone ring rotation was identified as another important contributor. Yet the most important factors were found to be the bond length alternation and bond order alternation that were linearly correlated to the absorption maximum by up to 62 and 82%, respectively. We ascribe this novel insight into the structural basis of the absorption spectrum to our enhanced protein setup that includes membrane embedding as well as long and extensive sampling.
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Affiliation(s)
- Suliman Adam
- Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Christian Wiebeler
- Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Igor Schapiro
- Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
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12
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Zuehlsdorff TJ, Shedge SV, Lu SY, Hong H, Aguirre VP, Shi L, Isborn CM. Vibronic and Environmental Effects in Simulations of Optical Spectroscopy. Annu Rev Phys Chem 2021; 72:165-188. [DOI: 10.1146/annurev-physchem-090419-051350] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Including both environmental and vibronic effects is important for accurate simulation of optical spectra, but combining these effects remains computationally challenging. We outline two approaches that consider both the explicit atomistic environment and the vibronic transitions. Both phenomena are responsible for spectral shapes in linear spectroscopy and the electronic evolution measured in nonlinear spectroscopy. The first approach utilizes snapshots of chromophore-environment configurations for which chromophore normal modes are determined. We outline various approximations for this static approach that assumes harmonic potentials and ignores dynamic system-environment coupling. The second approach obtains excitation energies for a series of time-correlated snapshots. This dynamic approach relies on the accurate truncation of the cumulant expansion but treats the dynamics of the chromophore and the environment on equal footing. Both approaches show significant potential for making strides toward more accurate optical spectroscopy simulations of complex condensed phase systems.
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Affiliation(s)
- Tim J. Zuehlsdorff
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Sapana V. Shedge
- Department of Chemistry and Chemical Biology, University of California, Merced, California 95343, USA
| | - Shao-Yu Lu
- Department of Chemistry and Chemical Biology, University of California, Merced, California 95343, USA
| | - Hanbo Hong
- Department of Chemistry and Chemical Biology, University of California, Merced, California 95343, USA
| | - Vincent P. Aguirre
- Department of Chemistry and Chemical Biology, University of California, Merced, California 95343, USA
| | - Liang Shi
- Department of Chemistry and Chemical Biology, University of California, Merced, California 95343, USA
| | - Christine M. Isborn
- Department of Chemistry and Chemical Biology, University of California, Merced, California 95343, USA
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13
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Shedge SV, Zuehlsdorff TJ, Khanna A, Conley S, Isborn CM. Explicit environmental and vibronic effects in simulations of linear and nonlinear optical spectroscopy. J Chem Phys 2021; 154:084116. [PMID: 33639769 DOI: 10.1063/5.0038196] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Accurately simulating the linear and nonlinear electronic spectra of condensed phase systems and accounting for all physical phenomena contributing to spectral line shapes presents a significant challenge. Vibronic transitions can be captured through a harmonic model generated from the normal modes of a chromophore, but it is challenging to also include the effects of specific chromophore-environment interactions within such a model. We work to overcome this limitation by combining approaches to account for both explicit environment interactions and vibronic couplings for simulating both linear and nonlinear optical spectra. We present and show results for three approaches of varying computational cost for combining ensemble sampling of chromophore-environment configurations with Franck-Condon line shapes for simulating linear spectra. We present two analogous approaches for nonlinear spectra. Simulated absorption spectra and two-dimensional electronic spectra (2DES) are presented for the Nile red chromophore in different solvent environments. Employing an average Franck-Condon or 2DES line shape appears to be a promising method for simulating linear and nonlinear spectroscopy for a chromophore in the condensed phase.
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Affiliation(s)
- Sapana V Shedge
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Tim J Zuehlsdorff
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Ajay Khanna
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Stacey Conley
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Christine M Isborn
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
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14
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Fernández-Alarcón A, Guevara-Vela JM, Casals-Sainz JL, Costales A, Francisco E, Martín Pendás Á, Rocha Rinza T. Photochemistry in Real Space: Batho- and Hypsochromism in the Water Dimer. Chemistry 2020; 26:17035-17045. [PMID: 32822523 DOI: 10.1002/chem.202002854] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Indexed: 11/09/2022]
Abstract
The development of chemical intuition in photochemistry faces several difficulties that result from the inadequacy of the one-particle picture, the Born-Oppenheimer approximation, and other basic ideas used to build models. It is shown herein how real-space approaches can be efficiently used to gain valuable insights in photochemistry through a simple example of red and blue shift effects: the double hypso- and bathochromic shifts in the low-lying valence excited states of (H2 O)2 . It is demonstrated that 1) the use of these techniques allows the perturbative language used in the theory of intermolecular interactions, even in the strongly interacting short-range regime, to be maintained; 2) one and only one molecule is photoexcited in each of the addressed excited states and 3) the electrostatic interaction between the in-the-cluster molecular dipoles provides a fairly intuitive rationalisation of the observed batho- and hypsochromism. The methods exploited and illustrated herein are able to maintain the individuality and properties of the interacting entities in a molecular aggregate, and thereby they allow chemical intuition in general states, at any geometry and using a broad variety of electronic structure methods to be kept and built.
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Affiliation(s)
- Alberto Fernández-Alarcón
- Institute of Chemistry, National Autonomous University of Mexico, 04510, Mexico City, Mexico.,Department of Analytical and Physical Chemistry, University of Oviedo, 33006, Oviedo, Spain
| | | | - José Luis Casals-Sainz
- Department of Analytical and Physical Chemistry, University of Oviedo, 33006, Oviedo, Spain
| | - Aurora Costales
- Department of Analytical and Physical Chemistry, University of Oviedo, 33006, Oviedo, Spain
| | - Evelio Francisco
- Department of Analytical and Physical Chemistry, University of Oviedo, 33006, Oviedo, Spain
| | - Ángel Martín Pendás
- Department of Analytical and Physical Chemistry, University of Oviedo, 33006, Oviedo, Spain
| | - Tomás Rocha Rinza
- Institute of Chemistry, National Autonomous University of Mexico, 04510, Mexico City, Mexico
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15
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Hernández-Rodríguez EW, Escorcia AM, van der Kamp MW, Montero-Alejo AL, Caballero J. Multi-scale simulation reveals that an amino acid substitution increases photosensitizing reaction inputs in Rhodopsins. J Comput Chem 2020; 41:2278-2295. [PMID: 32757375 DOI: 10.1002/jcc.26392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Revised: 06/27/2020] [Accepted: 07/04/2020] [Indexed: 11/11/2022]
Abstract
Evaluating the availability of molecular oxygen (O2 ) and energy of excited states in the retinal binding site of rhodopsin is a crucial challenging first step to understand photosensitizing reactions in wild-type (WT) and mutant rhodopsins by absorbing visible light. In the present work, energies of the ground and excited states related to 11-cis-retinal and the O2 accessibility to the β-ionone ring are evaluated inside WT and human M207R mutant rhodopsins. Putative O2 pathways within rhodopsins are identified by using molecular dynamics simulations, Voronoi-diagram analysis, and implicit ligand sampling while retinal energetic properties are investigated through density functional theory, and quantum mechanical/molecular mechanical methods. Here, the predictions reveal that an amino acid substitution can lead to enough energy and O2 accessibility in the core hosting retinal of mutant rhodopsins to favor the photosensitized singlet oxygen generation, which can be useful in understanding retinal degeneration mechanisms and in designing blue-lighting-absorbing proteic photosensitizers.
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Affiliation(s)
- Erix W Hernández-Rodríguez
- Laboratorio de Bioinformática y Química Computacional, Escuela de Química y Farmacia, Facultad de Medicina, Universidad Católica del Maule, Talca, Chile
| | - Andrés M Escorcia
- School of Biochemistry, University of Bristol, University Walk, Bristol, UK
| | | | - Ana L Montero-Alejo
- Departamento de Física, Facultad de Ciencias Naturales, Matemática y del Medio Ambiente (FCNMM), Universidad Tecnológica Metropolitana, Santiago, Chile
| | - Julio Caballero
- Departamento de Bioinformática, Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile
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16
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Zuehlsdorff TJ, Hong H, Shi L, Isborn CM. Nonlinear spectroscopy in the condensed phase: The role of Duschinsky rotations and third order cumulant contributions. J Chem Phys 2020; 153:044127. [PMID: 32752702 DOI: 10.1063/5.0013739] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
First-principles modeling of nonlinear optical spectra in the condensed phase is highly challenging because both environment and vibronic interactions can play a large role in determining spectral shapes and excited state dynamics. Here, we compute two dimensional electronic spectroscopy (2DES) signals based on a cumulant expansion of the energy gap fluctuation operator, with specific focus on analyzing mode mixing effects introduced by the Duschinsky rotation and the role of the third order term in the cumulant expansion for both model and realistic condensed phase systems. We show that for a harmonic model system, the third order cumulant correction captures effects introduced by a mismatch in curvatures of ground and excited state potential energy surfaces, as well as effects of mode mixing. We also demonstrate that 2DES signals can be accurately reconstructed from purely classical correlation functions using quantum correction factors. We then compute nonlinear optical spectra for the Nile red and methylene blue chromophores in solution, assessing the third order cumulant contribution for realistic systems. We show that the third order cumulant correction is strongly dependent on the treatment of the solvent environment, revealing the interplay between environmental polarization and the electronic-vibrational coupling.
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Affiliation(s)
- Tim J Zuehlsdorff
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Hanbo Hong
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Liang Shi
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Christine M Isborn
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
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17
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Cuzzocrea A, Scemama A, Briels WJ, Moroni S, Filippi C. Variational Principles in Quantum Monte Carlo: The Troubled Story of Variance Minimization. J Chem Theory Comput 2020; 16:4203-4212. [PMID: 32419451 PMCID: PMC7365558 DOI: 10.1021/acs.jctc.0c00147] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
![]()
We
investigate the use of different variational principles in quantum
Monte Carlo, namely, energy and variance minimization, prompted by
the interest in the robust and accurate estimation of electronic excited
states. For two prototypical, challenging molecules, we readily reach
the accuracy of the best available reference excitation energies using
energy minimization in a state-specific or state-average fashion for
states of different or equal symmetry, respectively. On the other
hand, in variance minimization, where the use of suitable functionals
is expected to target specific states regardless of the symmetry,
we encounter severe problems for a variety of wave functions: as the
variance converges, the energy drifts away from that of the selected
state. This unexpected behavior is sometimes observed even when the
target is the ground state and generally prevents the robust estimation
of total and excitation energies. We analyze this problem using a
very simple wave function and infer that the optimization finds little
or no barrier to escape from a local minimum or local plateau, eventually
converging to a lower-variance state instead of the target state.
For the increasingly complex systems becoming in reach of quantum
Monte Carlo simulations, variance minimization with current functionals
appears to be an impractical route.
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Affiliation(s)
- Alice Cuzzocrea
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Anthony Scemama
- Laboratoire de Chimie et Physique Quantiques, Université de Toulouse, CNRS, UPS, 118 route de Narbonne, 31062 Toulouse Cedex 09, France
| | - Wim J Briels
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Saverio Moroni
- CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali, Via Bonomea 265, I-34136 Trieste, Italy.,SISSA Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, I-34136 Trieste, Italy
| | - Claudia Filippi
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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18
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Li W. Residue-Residue Mutual Work Analysis of Retinal-Opsin Interaction in Rhodopsin: Implications for Protein-Ligand Binding. J Chem Theory Comput 2020; 16:1834-1842. [PMID: 31972074 DOI: 10.1021/acs.jctc.9b01035] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Energetic contributions at the single-residue level for retinal-opsin interactions in rhodopsin were studied by combining molecular dynamics simulations, transition path sampling, and a newly developed energy decomposition approach. The virtual work at an infinitesimal time interval was decomposed into the work components on one residue due to its interaction with another residue, which were then averaged over the transition path ensemble along a proposed reaction coordinate. Such residue-residue mutual work analysis on 62 residues within the active center of rhodopsin resulted in a very sparse interaction matrix, which is generally not symmetric but antisymmetric to some extent. Fourteen residues were identified to be major players in retinal relaxation along a plausible pathway from bathorhodopsin to the blue-shifted intermediate, which is in good agreement with an existing NMR study. Based on the matrix of mutual work, a comprehensive network was constructed to provide detailed insights into the chromophore-protein interaction from a viewpoint of energy flow.
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Affiliation(s)
- Wenjin Li
- Institute for Advanced Study, Shenzhen University, Shenzhen, China
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19
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Shao Y, Mei Y, Sundholm D, Kaila VRI. Benchmarking the Performance of Time-Dependent Density Functional Theory Methods on Biochromophores. J Chem Theory Comput 2020; 16:587-600. [PMID: 31815476 PMCID: PMC7391796 DOI: 10.1021/acs.jctc.9b00823] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Quantum chemical calculations are important for elucidating light-capturing mechanisms in photobiological systems. The time-dependent density functional theory (TDDFT) has become a popular methodology because of its balance between accuracy and computational scaling, despite its problems in describing, for example, charge transfer states. As a step toward systematically understanding the performance of TDDFT calculations on biomolecular systems, we study here 17 commonly used density functionals, including seven long-range separated functionals, and compare the obtained results with excitation energies calculated at the approximate second order coupled-cluster theory level (CC2). The benchmarking set includes the first five singlet excited states of 11 chemical analogues of biochromophores from the green fluorescent protein, rhodopsin/bacteriorhodopsin (Rh/bR), and the photoactive yellow protein. We find that commonly used pure density functionals such as BP86, PBE, M11-L, and hybrid functionals with 20-25% of Hartree-Fock (HF) exchange (B3LYP, PBE0) have a tendency to consistently underestimate vertical excitation energies (VEEs) relative to the CC2 values, whereas hybrid density functionals with around 50% HF exchange such as BHLYP, PBE50, and M06-2X and long-range corrected functionals such as CAM-B3LYP, ωPBE, ωPBEh, ωB97X, ωB97XD, BNL, and M11 overestimate the VEEs. We observe that calculations using the CAM-B3LYP and ωPBEh functionals with 65% and 100% long-range HF exchange, respectively, lead to an overestimation of the VEEs by 0.2-0.3 eV for the benchmarking set. To reduce the systematic error, we introduce here two new empirical functionals, CAMh-B3LYP and ωhPBE0, for which we adjusted the long-range HF exchange to 50%. The introduced parameterization reduces the mean signed average (MSA) deviation to 0.07 eV and the root mean square (rms) deviation to 0.17 eV as compared to the CC2 values. In the present study, TDDFT calculations using the aug-def2-TZVP basis sets, the best performing functionals relative to CC2 are ωhPBE0 (rms = 0.17, MSA = 0.06 eV); CAMh-B3LYP (rms = 0.16, MSA = 0.07 eV); and PBE0 (rms = 0.23, MSA = -0.14 eV). For the popular range-separated CAM-B3LYP functional, we obtain an rms value of 0.31 eV and an MSA value of 0.25 eV, which can be compared with the rms and MSA values of 0.37 and -0.31 eV, respectively, as obtained at the B3LYP level.
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Affiliation(s)
- Yihan Shao
- Department of Chemistry and Biochemistry , University of Oklahoma , Norman , Oklahoma 73019 , United States
| | - Ye Mei
- State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science , East China Normal University , Shanghai 200062 , China
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai , Shanghai 200062 , China
| | - Dage Sundholm
- Department of Chemistry, Faculty of Science , University of Helsinki , P.O. Box 55, Helsinki FIN-00014 , Finland
| | - Ville R I Kaila
- Department Chemie , Technische Universität München (TUM) , Lichtenbergstrasse 4 , Garching D-85747 , Germany
- Department of Biochemistry and Biophysics , Stockholm University , Stockholm SE-10691 , Sweden
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20
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Zuehlsdorff TJ, Hong H, Shi L, Isborn CM. Influence of Electronic Polarization on the Spectral Density. J Phys Chem B 2019; 124:531-543. [DOI: 10.1021/acs.jpcb.9b10250] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Tim J. Zuehlsdorff
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, United States
| | - Hanbo Hong
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, United States
| | - Liang Shi
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, United States
| | - Christine M. Isborn
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, United States
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21
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Dash M, Feldt J, Moroni S, Scemama A, Filippi C. Excited States with Selected Configuration Interaction-Quantum Monte Carlo: Chemically Accurate Excitation Energies and Geometries. J Chem Theory Comput 2019; 15:4896-4906. [PMID: 31348645 PMCID: PMC6740157 DOI: 10.1021/acs.jctc.9b00476] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We employ quantum Monte Carlo to obtain chemically accurate vertical and adiabatic excitation energies, and equilibrium excited-state structures for the small, yet challenging, formaldehyde and thioformaldehyde molecules. A key ingredient is a robust protocol to obtain balanced ground- and excited-state Jastrow-Slater wave functions at a given geometry, and to maintain such a balanced description as we relax the structure in the excited state. We use determinantal components generated via a selected configuration interaction scheme which targets the same second-order perturbation energy correction for all states of interest at different geometries, and fully optimize all variational parameters in the resultant Jastrow-Slater wave functions. Importantly, the excitation energies as well as the structural parameters in the ground and excited states are converged with very compact wave functions comprising few thousand determinants in a minimally augmented double-ζ basis set. These results are obtained already at the variational Monte Carlo level, the more accurate diffusion Monte Carlo method yielding only a small improvement in the adiabatic excitation energies. We find that matching Jastrow-Slater wave functions with similar variances can yield excitation energies compatible with our best estimates; however, the variance-matching procedure requires somewhat larger determinantal expansions to achieve the same accuracy, and it is less straightforward to adapt during structural optimization in the excited state.
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Affiliation(s)
- Monika Dash
- MESA+ Institute for Nanotechnology , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
| | - Jonas Feldt
- MESA+ Institute for Nanotechnology , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
| | - Saverio Moroni
- CNR-IOM DEMOCRITOS , Istituto Officina dei Materiali and SISSA Scuola Internazionale Superiore di Studi Avanzati , Via Bonomea 265 , I-34136 Trieste , Italy
| | - Anthony Scemama
- Laboratoire de Chimie et Physique Quantiques , Université de Toulouse, CNRS, UPS , 31062 Toulouse , France
| | - Claudia Filippi
- MESA+ Institute for Nanotechnology , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
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22
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Shedge SV, Zuehlsdorff TJ, Servis MJ, Clark AE, Isborn CM. Effect of Ions on the Optical Absorption Spectra of Aqueously Solvated Chromophores. J Phys Chem A 2019; 123:6175-6184. [DOI: 10.1021/acs.jpca.9b03163] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Sapana V. Shedge
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, United States
| | - Tim J. Zuehlsdorff
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, United States
| | - Michael J. Servis
- Department of Chemistry and the Material Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
| | - Aurora E. Clark
- Department of Chemistry and the Material Science and Engineering Program, Washington State University, Pullman, Washington 99164, United States
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, United States
| | - Christine M. Isborn
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, United States
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23
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Pedraza-González L, De Vico L, del Carmen Marín M, Fanelli F, Olivucci M. a-ARM: Automatic Rhodopsin Modeling with Chromophore Cavity Generation, Ionization State Selection, and External Counterion Placement. J Chem Theory Comput 2019; 15:3134-3152. [PMID: 30916955 PMCID: PMC7141608 DOI: 10.1021/acs.jctc.9b00061] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Automatic Rhodopsin Modeling (ARM) protocol has recently been proposed as a tool for the fast and parallel generation of basic hybrid quantum mechanics/molecular mechanics (QM/MM) models of wild type and mutant rhodopsins. However, in its present version, input preparation requires a few hours long user's manipulation of the template protein structure, which also impairs the reproducibility of the generated models. This limitation, which makes model building semiautomatic rather than fully automatic, comprises four tasks: definition of the retinal chromophore cavity, assignment of protonation states of the ionizable residues, neutralization of the protein with external counterions, and finally congruous generation of single or multiple mutations. In this work, we show that the automation of the original ARM protocol can be extended to a level suitable for performing the above tasks without user's manipulation and with an input preparation time of minutes. The new protocol, called a-ARM, delivers fully reproducible (i.e., user independent) rhodopsin QM/MM models as well as an improved model quality. More specifically, we show that the trend in vertical excitation energies observed for a set of 25 wild type and 14 mutant rhodopsins is predicted by the new protocol better than when using the original. Such an agreement is reflected by an estimated (relative to the probed set) trend deviation of 0.7 ± 0.5 kcal mol-1 (0.03 ± 0.02 eV) and mean absolute error of 1.0 kcal mol-1 (0.04 eV).
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Affiliation(s)
- Laura Pedraza-González
- Department of Biotechnologies, Chemistry and Pharmacy, Università degli Studi di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - Luca De Vico
- Department of Biotechnologies, Chemistry and Pharmacy, Università degli Studi di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - María del Carmen Marín
- Department of Biotechnologies, Chemistry and Pharmacy, Università degli Studi di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - Francesca Fanelli
- Department of Life Sciences, Center for Neuroscience and Neurotechnology, Università degli Studi di Modena e Reggio Emilia, I-41125 Modena, Italy
| | - Massimo Olivucci
- Department of Biotechnologies, Chemistry and Pharmacy, Università degli Studi di Siena, via A. Moro 2, I-53100 Siena, Italy
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
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24
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Mai S, Gattuso H, Monari A, González L. Novel Molecular-Dynamics-Based Protocols for Phase Space Sampling in Complex Systems. Front Chem 2018; 6:495. [PMID: 30386775 PMCID: PMC6199692 DOI: 10.3389/fchem.2018.00495] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 09/27/2018] [Indexed: 11/13/2022] Open
Abstract
The adequate exploration of the phase space of a chromophore is a fundamental necessity for the simulation of their optical and photophysical properties, taking into account the effects of vibrational motion and, most importantly, the coupling with a (non-homogeneous) molecular environment. A representative set of conformational snapshots around the Franck-Condon region is also required to perform non-adiabatic molecular dynamics, for instance in the framework of surface hopping. Indeed, in the latter case one needs to prepare a set of initial conditions providing a meaningful and complete statistical base for the subsequent trajectory propagation. In this contribution, we propose two new protocols for molecular dynamics-based phase space sampling, called "local temperature adjustment" and "individual QM/MM-based relaxation." These protocols are intended for situations in which the popular Wigner distribution sampling procedure is not applicable-as it is the case when anharmonic or nonlinear vibrations are present-and where regular molecular dynamics sampling might suffer from an inaccurate distribution of internal energy or from inaccurate force fields. The new protocols are applied to the case of phase space sampling of [Re(CO)3(Im)(Phen)]+ (im, imidazole; phen, phenanthroline) in aqueous solution, showing the advantages and limitations of regular Wigner and molecular dynamics sampling as well as the strengths of the new protocols.
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Affiliation(s)
- Sebastian Mai
- Faculty of Chemistry, Institute of Theoretical Chemistry, University of Vienna, Vienna, Austria
| | - Hugo Gattuso
- Université de Lorraine and CNRS, LPTC UMR 7019, Nancy, France
| | - Antonio Monari
- Université de Lorraine and CNRS, LPTC UMR 7019, Nancy, France
| | - Leticia González
- Faculty of Chemistry, Institute of Theoretical Chemistry, University of Vienna, Vienna, Austria
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25
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Zuehlsdorff TJ, Napoli JA, Milanese JM, Markland TE, Isborn CM. Unraveling electronic absorption spectra using nuclear quantum effects: Photoactive yellow protein and green fluorescent protein chromophores in water. J Chem Phys 2018; 149:024107. [PMID: 30007372 DOI: 10.1063/1.5025517] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Many physical phenomena must be accounted for to accurately model solution-phase optical spectral line shapes, from the sampling of chromophore-solvent configurations to the electronic-vibrational transitions leading to vibronic fine structure. Here we thoroughly explore the role of nuclear quantum effects, direct and indirect solvent effects, and vibronic effects in the computation of the optical spectrum of the aqueously solvated anionic chromophores of green fluorescent protein and photoactive yellow protein. By analyzing the chromophore and solvent configurations, the distributions of vertical excitation energies, the absorption spectra computed within the ensemble approach, and the absorption spectra computed within the ensemble plus zero-temperature Franck-Condon approach, we show how solvent, nuclear quantum effects, and vibronic transitions alter the optical absorption spectra. We find that including nuclear quantum effects in the sampling of chromophore-solvent configurations using ab initio path integral molecular dynamics simulations leads to improved spectral shapes through three mechanisms. The three mechanisms that lead to line shape broadening and a better description of the high-energy tail are softening of heavy atom bonds in the chromophore that couple to the optically bright state, widening the distribution of vertical excitation energies from more diverse solvation environments, and redistributing spectral weight from the 0-0 vibronic transition to higher energy vibronic transitions when computing the Franck-Condon spectrum in a frozen solvent pocket. The absorption spectra computed using the combined ensemble plus zero-temperature Franck-Condon approach yield significant improvements in spectral shape and width compared to the spectra computed with the ensemble approach. Using the combined approach with configurations sampled from path integral molecular dynamics trajectories presents a significant step forward in accurately modeling the absorption spectra of aqueously solvated chromophores.
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Affiliation(s)
- Tim J Zuehlsdorff
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Joseph A Napoli
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Joel M Milanese
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
| | - Thomas E Markland
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Christine M Isborn
- Chemistry and Chemical Biology, University of California Merced, Merced, California 95343, USA
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26
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Wolański Ł, Grabarek D, Andruniów T. Is the choice of a standard zeroth-order hamiltonian in CASPT2 ansatz optimal in calculations of excitation energies in protonated and unprotonated schiff bases of retinal? J Comput Chem 2018; 39:1470-1480. [PMID: 29635695 DOI: 10.1002/jcc.25217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 03/09/2018] [Accepted: 03/10/2018] [Indexed: 11/07/2022]
Abstract
To account for systematic error of CASPT2 method empirical modification of the zeroth-order Hamiltonian with Ionization Potential-Electron Affinity (IPEA) shift was introduced. The optimized IPEA value (0.25 a.u.), called standard IPEA (S-IPEA), was recommended but due to its unsatisfactory performance in multiple metallic and organic compounds it has been questioned lately as a general parameter working properly for all molecules under CASPT2 study. As we are interested in Schiff bases of retinal, an important question emerging from this conflict of choice, to use or not to use S-IPEA, is whether the introduction of the modified zeroth-order Hamiltonian into CASPT2 ansatz does really improve their energetics. To achieve this goal, we assessed an impact of the IPEA shift value, in a range of 0-0.35 a.u., on vertical excitation energies to low-lying singlet states of two protonated (RPSBs) and two unprotonated (RSBs) Schiff bases of retinal for which experimental data in gas phase are available. In addition, an effect of geometry, basis set, and active space on computed VEEs is also reported. We find, that for these systems, the choice of S-IPEA significantly overestimates both S0 →S1 and S0 →S2 energies and the best theoretical estimate, in reference to the experimental data, is provided with either unmodified zeroth-order Hamiltonian or small value of the IPEA shift in a range of 0.05-0.15 a.u., depending on active space and basis set size, equilibrium geometry, and character of the excited state. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Łukasz Wolański
- Advanced Materials Engineering and Modelling Group, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, Wroclaw, 50-370, Poland
| | - Dawid Grabarek
- Advanced Materials Engineering and Modelling Group, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, Wroclaw, 50-370, Poland
| | - Tadeusz Andruniów
- Advanced Materials Engineering and Modelling Group, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, Wroclaw, 50-370, Poland
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27
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Zuehlsdorff TJ, Isborn CM. Combining the ensemble and Franck-Condon approaches for calculating spectral shapes of molecules in solution. J Chem Phys 2018; 148:024110. [PMID: 29331131 DOI: 10.1063/1.5006043] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The correct treatment of vibronic effects is vital for the modeling of absorption spectra of many solvated dyes. Vibronic spectra for small dyes in solution can be easily computed within the Franck-Condon approximation using an implicit solvent model. However, implicit solvent models neglect specific solute-solvent interactions on the electronic excited state. On the other hand, a straightforward way to account for solute-solvent interactions and temperature-dependent broadening is by computing vertical excitation energies obtained from an ensemble of solute-solvent conformations. Ensemble approaches usually do not account for vibronic transitions and thus often produce spectral shapes in poor agreement with experiment. We address these shortcomings by combining zero-temperature vibronic fine structure with vertical excitations computed for a room-temperature ensemble of solute-solvent configurations. In this combined approach, all temperature-dependent broadening is treated classically through the sampling of configurations and quantum mechanical vibronic contributions are included as a zero-temperature correction to each vertical transition. In our calculation of the vertical excitations, significant regions of the solvent environment are treated fully quantum mechanically to account for solute-solvent polarization and charge-transfer. For the Franck-Condon calculations, a small amount of frozen explicit solvent is considered in order to capture solvent effects on the vibronic shape function. We test the proposed method by comparing calculated and experimental absorption spectra of Nile red and the green fluorescent protein chromophore in polar and non-polar solvents. For systems with strong solute-solvent interactions, the combined approach yields significant improvements over the ensemble approach. For systems with weak to moderate solute-solvent interactions, both the high-energy vibronic tail and the width of the spectra are in excellent agreement with experiments.
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Affiliation(s)
- T J Zuehlsdorff
- School of Natural Sciences, University of California Merced, N. Lake Road, Merced, California 95344, USA
| | - C M Isborn
- School of Natural Sciences, University of California Merced, N. Lake Road, Merced, California 95344, USA
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28
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Bircher MP, Rothlisberger U. Plane-Wave Implementation and Performance of à-la-Carte Coulomb-Attenuated Exchange-Correlation Functionals for Predicting Optical Excitation Energies in Some Notorious Cases. J Chem Theory Comput 2018; 14:3184-3195. [DOI: 10.1021/acs.jctc.8b00069] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Martin P. Bircher
- Laboratoire de Chimie et Biochimie Computationnelles, Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland
| | - Ursula Rothlisberger
- Laboratoire de Chimie et Biochimie Computationnelles, Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland
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29
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Abstract
Channelrhodopsin-2 (ChR2) is a light-sensitive ion channel widely used in optogenetics. Photoactivation triggers a trans-to-cis isomerization of a covalently bound retinal. Ensuing conformational changes open a cation-selective channel. We explore the structural dynamics in the early photocycle leading to channel opening by classical (MM) and quantum mechanical (QM) molecular simulations. With QM/MM simulations, we generated a protein-adapted force field for the retinal chromophore, which we validated against absorption spectra. In a 4-µs MM simulation of a dark-adapted ChR2 dimer, water entered the vestibules of the closed channel. Retinal all-trans to 13-cis isomerization, simulated with metadynamics, triggered a major restructuring of the charge cluster forming the channel gate. On a microsecond time scale, water penetrated the gate to form a membrane-spanning preopen pore between helices H1, H2, H3, and H7. This influx of water into an ion-impermeable preopen pore is consistent with time-resolved infrared spectroscopy and electrophysiology experiments. In the retinal 13-cis state, D253 emerged as the proton acceptor of the Schiff base. Upon proton transfer from the Schiff base to D253, modeled by QM/MM simulations, we obtained an early-M/P2390-like intermediate. Rapid rotation of the unprotonated Schiff base toward the cytosolic side effectively prevents its reprotonation from the extracellular side. From MM and QM simulations, we gained detailed insight into the mechanism of ChR2 photoactivation and early events in pore formation. By rearranging the network of charges and hydrogen bonds forming the gate, water emerges as a key player in light-driven ChR2 channel opening.
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Affiliation(s)
- Albert Ardevol
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany;
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany;
- Department of Physics, Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
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30
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Marcolongo JP, Zeida A, Semelak JA, Foglia NO, Morzan UN, Estrin DA, González Lebrero MC, Scherlis DA. Chemical Reactivity and Spectroscopy Explored From QM/MM Molecular Dynamics Simulations Using the LIO Code. Front Chem 2018; 6:70. [PMID: 29619365 PMCID: PMC5871697 DOI: 10.3389/fchem.2018.00070] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 03/05/2018] [Indexed: 12/13/2022] Open
Abstract
In this work we present the current advances in the development and the applications of LIO, a lab-made code designed for density functional theory calculations in graphical processing units (GPU), that can be coupled with different classical molecular dynamics engines. This code has been thoroughly optimized to perform efficient molecular dynamics simulations at the QM/MM DFT level, allowing for an exhaustive sampling of the configurational space. Selected examples are presented for the description of chemical reactivity in terms of free energy profiles, and also for the computation of optical properties, such as vibrational and electronic spectra in solvent and protein environments.
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Affiliation(s)
- Juan P Marcolongo
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Ari Zeida
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.,Departamento de Bioquímica and Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Jonathan A Semelak
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Nicolás O Foglia
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Uriel N Morzan
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Dario A Estrin
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Mariano C González Lebrero
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Damián A Scherlis
- DQIAyQF, INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
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31
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Morzan UN, Alonso de Armiño DJ, Foglia NO, Ramírez F, González Lebrero MC, Scherlis DA, Estrin DA. Spectroscopy in Complex Environments from QM–MM Simulations. Chem Rev 2018; 118:4071-4113. [DOI: 10.1021/acs.chemrev.8b00026] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Uriel N. Morzan
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Diego J. Alonso de Armiño
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Nicolás O. Foglia
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Francisco Ramírez
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Mariano C. González Lebrero
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Damián A. Scherlis
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
| | - Darío A. Estrin
- Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, C1428EHA Buenos Aires, Argentina
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32
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Mussard B, Coccia E, Assaraf R, Otten M, Umrigar CJ, Toulouse J. Time-Dependent Linear-Response Variational Monte Carlo. ADVANCES IN QUANTUM CHEMISTRY 2018. [DOI: 10.1016/bs.aiq.2017.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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33
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El Hage K, Brickel S, Hermelin S, Gaulier G, Schmidt C, Bonacina L, van Keulen SC, Bhattacharyya S, Chergui M, Hamm P, Rothlisberger U, Wolf JP, Meuwly M. Implications of short time scale dynamics on long time processes. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2017; 4:061507. [PMID: 29308419 PMCID: PMC5741438 DOI: 10.1063/1.4996448] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/15/2017] [Indexed: 05/02/2023]
Abstract
This review provides a comprehensive overview of the structural dynamics in topical gas- and condensed-phase systems on multiple length and time scales. Starting from vibrationally induced dissociation of small molecules in the gas phase, the question of vibrational and internal energy redistribution through conformational dynamics is further developed by considering coupled electron/proton transfer in a model peptide over many orders of magnitude. The influence of the surrounding solvent is probed for electron transfer to the solvent in hydrated I-. Next, the dynamics of a modified PDZ domain over many time scales is analyzed following activation of a photoswitch. The hydration dynamics around halogenated amino acid side chains and their structural dynamics in proteins are relevant for iodinated TyrB26 insulin. Binding of nitric oxide to myoglobin is a process for which experimental and computational analyses have converged to a common view which connects rebinding time scales and the underlying dynamics. Finally, rhodopsin is a paradigmatic system for multiple length- and time-scale processes for which experimental and computational methods provide valuable insights into the functional dynamics. The systems discussed here highlight that for a comprehensive understanding of how structure, flexibility, energetics, and dynamics contribute to functional dynamics, experimental studies in multiple wavelength regions and computational studies including quantum, classical, and more coarse grained levels are required.
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Affiliation(s)
- Krystel El Hage
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Sebastian Brickel
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Sylvain Hermelin
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Geoffrey Gaulier
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Cédric Schmidt
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Luigi Bonacina
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Siri C van Keulen
- Institute of Chemical Sciences and Engineering, EPFL, Lausanne, Switzerland
| | | | - Majed Chergui
- Institute of Chemical Sciences and Engineering, EPFL, Lausanne, Switzerland
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | | | - Jean-Pierre Wolf
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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34
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Gozem S, Luk HL, Schapiro I, Olivucci M. Theory and Simulation of the Ultrafast Double-Bond Isomerization of Biological Chromophores. Chem Rev 2017; 117:13502-13565. [DOI: 10.1021/acs.chemrev.7b00177] [Citation(s) in RCA: 175] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Samer Gozem
- Department
of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Hoi Ling Luk
- Chemistry
Department, Bowling Green State University, Overman Hall, Bowling Green, Ohio 43403, United States
| | - Igor Schapiro
- Fritz
Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Massimo Olivucci
- Chemistry
Department, Bowling Green State University, Overman Hall, Bowling Green, Ohio 43403, United States
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università di Siena, via A. Moro
2, 53100 Siena, Italy
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35
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Kamiya M, Hayashi S. Photoactivation Intermediates of a G-Protein Coupled Receptor Rhodopsin Investigated by a Hybrid Molecular Simulation. J Phys Chem B 2017; 121:3842-3852. [PMID: 28240904 DOI: 10.1021/acs.jpcb.6b13050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rhodopsin is a G-protein coupled receptor functioning as a photoreceptor for vision through photoactivation of a covalently bound ligand of a retinal protonated Schiff base chromophore. Despite the availability of structural information on the inactivated and activated forms of the receptor, the transition processes initiated by the photoabsorption have not been well understood. Here we theoretically examined the photoactivation processes by means of molecular dynamics (MD) simulations and ab initio quantum mechanical/molecular mechanical (QM/MM) free energy geometry optimizations which enabled accurate geometry determination of the ligand molecule in ample statistical conformational samples of the protein. Structures of the intermediate states of the activation process, blue-shifted intermediate and Lumi, as well as the dark state first generated by MD simulations and then refined by the QM/MM free energy geometry optimizations were characterized by large displacement of the β-ionone ring of retinal along with change in the hydrogen bond of the protonated Schiff base. The ab initio calculations of vibrational and electronic spectroscopic properties of those states well reproduced the experimental observations and successfully identified the molecular origins underlying the spectroscopic features. The structural evolution in the formation of the intermediates provides a molecular insight into the efficient activation processes of the receptor.
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Affiliation(s)
- Motoshi Kamiya
- Department of Chemistry, Graduate School of Science, Kyoto University , Kyoto 606-8502, Japan
| | - Shigehiko Hayashi
- Department of Chemistry, Graduate School of Science, Kyoto University , Kyoto 606-8502, Japan
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36
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Cui Q. Perspective: Quantum mechanical methods in biochemistry and biophysics. J Chem Phys 2017; 145:140901. [PMID: 27782516 DOI: 10.1063/1.4964410] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In this perspective article, I discuss several research topics relevant to quantum mechanical (QM) methods in biophysical and biochemical applications. Due to the immense complexity of biological problems, the key is to develop methods that are able to strike the proper balance of computational efficiency and accuracy for the problem of interest. Therefore, in addition to the development of novel ab initio and density functional theory based QM methods for the study of reactive events that involve complex motifs such as transition metal clusters in metalloenzymes, it is equally important to develop inexpensive QM methods and advanced classical or quantal force fields to describe different physicochemical properties of biomolecules and their behaviors in complex environments. Maintaining a solid connection of these more approximate methods with rigorous QM methods is essential to their transferability and robustness. Comparison to diverse experimental observables helps validate computational models and mechanistic hypotheses as well as driving further development of computational methodologies.
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Affiliation(s)
- Qiang Cui
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA
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37
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Xie P, Zhou P, Alsaedi A, Zhang Y. pH-dependent absorption spectra of rhodopsin mutant E113Q: On the role of counterions and protein. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 174:25-31. [PMID: 27865136 DOI: 10.1016/j.saa.2016.11.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 11/08/2016] [Accepted: 11/12/2016] [Indexed: 06/06/2023]
Abstract
The absorption spectra of bovine rhodopsin mutant E113Q in solutions were investigated at the molecular level by using a hybrid quantum mechanics/molecular mechanics (QM/MM) method. The calculations suggest the mechanism of the absorption variations of E113Q at different pH values. The results indicate that the polarizations of the counterions in the vicinity of Schiff base under protonation and unprotonation states of the mutant E113Q would be a crucial factor to change the energy gap of the retinal to tune the absorption spectra. Glu-181 residue, which is close to the chromophore, cannot serve as the counterion of the protonated Schiff base of E113Q in dark state. Moreover, the results of the absorption maximum in mutant E113Q with the various anions (Cl-, Br-, I- and NO3-) manifested that the mutant E113Q could have the potential for use as a template of anion biosensors at visible wavelength.
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Affiliation(s)
- Peng Xie
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, People's Republic of China
| | - Panwang Zhou
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, People's Republic of China
| | - Ahmed Alsaedi
- Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
| | - Yan Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, People's Republic of China.
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38
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Varsano D, Caprasecca S, Coccia E. Theoretical description of protein field effects on electronic excitations of biological chromophores. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:013002. [PMID: 27830666 DOI: 10.1088/0953-8984/29/1/013002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show their applications on paradigmatic systems, such as the light-harvesting complexes, rhodopsin and green fluorescent protein, emphasising the theoretical frameworks which are of common use in solid state physics, and emerging as promising tools for biomolecular systems.
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Affiliation(s)
- Daniele Varsano
- S3 Center, CNR Institute of Nanoscience, Via Campi 213/A, 41125 Modena, Italy
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39
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Introduction to the Variational Monte Carlo Method in Quantum Chemistry and Physics. VARIATIONAL METHODS IN MOLECULAR MODELING 2017. [DOI: 10.1007/978-981-10-2502-0_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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40
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Provorse MR, Peev T, Xiong C, Isborn CM. Convergence of Excitation Energies in Mixed Quantum and Classical Solvent: Comparison of Continuum and Point Charge Models. J Phys Chem B 2016; 120:12148-12159. [DOI: 10.1021/acs.jpcb.6b09176] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Makenzie R. Provorse
- Chemistry and Chemical Biology, University of California at Merced, Merced, California 95343, United States
| | - Thomas Peev
- Chemistry and Chemical Biology, University of California at Merced, Merced, California 95343, United States
| | - Chou Xiong
- Chemistry and Chemical Biology, University of California at Merced, Merced, California 95343, United States
| | - Christine M. Isborn
- Chemistry and Chemical Biology, University of California at Merced, Merced, California 95343, United States
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41
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Guareschi R, Valsson O, Curutchet C, Mennucci B, Filippi C. Electrostatic versus Resonance Interactions in Photoreceptor Proteins: The Case of Rhodopsin. J Phys Chem Lett 2016; 7:4547-4553. [PMID: 27786481 DOI: 10.1021/acs.jpclett.6b02043] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Light sensing in photoreceptor proteins is subtly modulated by the multiple interactions between the chromophoric unit and its binding pocket. Many theoretical and experimental studies have tried to uncover the fundamental origin of these interactions but reached contradictory conclusions as to whether electrostatics, polarization, or intrinsically quantum effects prevail. Here, we select rhodopsin as a prototypical photoreceptor system to reveal the molecular mechanism underlying these interactions and regulating the spectral tuning. Combining a multireference perturbation method and density functional theory with a classical but atomistic and polarizable embedding scheme, we show that accounting for electrostatics only leads to a qualitatively wrong picture, while a responsive environment can successfully capture both the classical and quantum dominant effects. Several residues are found to tune the excitation by both differentially stabilizing ground and excited states and through nonclassical "inductive resonance" interactions. The results obtained with such a quantum-in-classical model are validated against both experimental data and fully quantum calculations.
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Affiliation(s)
- Riccardo Guareschi
- MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Omar Valsson
- Department of Chemistry and Applied Bioscience, ETH Zurich and Facoltà di Informatica, Instituto di Scienze Computazionali, Università della Svizzera italiana , Via Giuseppe Buffi 13, CH-6900 Lugano, Switzerland
| | - Carles Curutchet
- Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona , Av. Joan XXIII, s/n 08028 Barcelona, Spain
| | - Benedetta Mennucci
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa , Via Giuseppe Moruzzi 13, 56124 Pisa, Italy
| | - Claudia Filippi
- MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands
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42
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Melaccio F, del Carmen Marín M, Valentini A, Montisci F, Rinaldi S, Cherubini M, Yang X, Kato Y, Stenrup M, Orozco-Gonzalez Y, Ferré N, Luk HL, Kandori H, Olivucci M. Toward Automatic Rhodopsin Modeling as a Tool for High-Throughput Computational Photobiology. J Chem Theory Comput 2016; 12:6020-6034. [DOI: 10.1021/acs.jctc.6b00367] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Federico Melaccio
- Department
of Biotechnology, Chemistry e Pharmacy, Università di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - María del Carmen Marín
- Department
of Biotechnology, Chemistry e Pharmacy, Università di Siena, via A. Moro 2, I-53100 Siena, Italy
- Department
of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Alessio Valentini
- Department
of Biotechnology, Chemistry e Pharmacy, Università di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - Fabio Montisci
- Department
of Biotechnology, Chemistry e Pharmacy, Università di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - Silvia Rinaldi
- Department
of Biotechnology, Chemistry e Pharmacy, Università di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - Marco Cherubini
- Department
of Biotechnology, Chemistry e Pharmacy, Università di Siena, via A. Moro 2, I-53100 Siena, Italy
| | - Xuchun Yang
- Department
of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Yoshitaka Kato
- Department
of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan
| | - Michael Stenrup
- Aix-Marseille Université, CNRS, ICR, 13284 Marseille, France
| | - Yoelvis Orozco-Gonzalez
- Department
of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
- Institut
de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 Université de Strasbourg-CNRS, F-67034 Strasbourg, France
- USIAS
Institut d’Études Avancées, Université de Strasbourg, 5 allée du Général Rouvillois, F-67083 Strasbourg, France
| | - Nicolas Ferré
- Aix-Marseille Université, CNRS, ICR, 13284 Marseille, France
| | - Hoi Ling Luk
- Department
of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Hideki Kandori
- Department
of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Japan
| | - Massimo Olivucci
- Department
of Biotechnology, Chemistry e Pharmacy, Università di Siena, via A. Moro 2, I-53100 Siena, Italy
- Department
of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
- Institut
de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 Université de Strasbourg-CNRS, F-67034 Strasbourg, France
- USIAS
Institut d’Études Avancées, Université de Strasbourg, 5 allée du Général Rouvillois, F-67083 Strasbourg, France
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43
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Hedegård ED, Reiher M. Polarizable Embedding Density Matrix Renormalization Group. J Chem Theory Comput 2016; 12:4242-53. [PMID: 27537835 DOI: 10.1021/acs.jctc.6b00476] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The polarizable embedding (PE) approach is a flexible embedding model where a preselected region out of a larger system is described quantum mechanically, while the interaction with the surrounding environment is modeled through an effective operator. This effective operator represents the environment by atom-centered multipoles and polarizabilities derived from quantum mechanical calculations on (fragments of) the environment. Thereby, the polarization of the environment is explicitly accounted for. Here, we present the coupling of the PE approach with the density matrix renormalization group (DMRG). This PE-DMRG method is particularly suitable for embedded subsystems that feature a dense manifold of frontier orbitals which requires large active spaces. Recovering such static electron-correlation effects in multiconfigurational electronic structure problems, while accounting for both electrostatics and polarization of a surrounding environment, allows us to describe strongly correlated electronic structures in complex molecular environments. We investigate various embedding potentials for the well-studied first excited state of water with active spaces that correspond to a full configuration-interaction treatment. Moreover, we study the environment effect on the first excited state of a retinylidene Schiff base within a channelrhodopsin protein. For this system, we also investigate the effect of dynamical correlation included through short-range density functional theory.
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Affiliation(s)
- Erik D Hedegård
- Laboratorium für Physikalische Chemie, ETH Zürich , Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Markus Reiher
- Laboratorium für Physikalische Chemie, ETH Zürich , Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
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Suomivuori CM, Lang L, Sundholm D, Gamiz-Hernandez AP, Kaila VRI. Tuning the Protein-Induced Absorption Shifts of Retinal in Engineered Rhodopsin Mimics. Chemistry 2016; 22:8254-61. [DOI: 10.1002/chem.201505126] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/23/2016] [Indexed: 11/12/2022]
Affiliation(s)
- Carl-Mikael Suomivuori
- Department of Chemistry; University of Helsinki; A.I. Virtanens plats 1, P.O. Box 55 FI-00014 Helsinki Finland
- Department Chemie; Technische Universität München (TUM); Lichtenbergstrasse 4 85747 Garching Germany
| | - Lucas Lang
- Department Chemie; Technische Universität München (TUM); Lichtenbergstrasse 4 85747 Garching Germany
| | - Dage Sundholm
- Department of Chemistry; University of Helsinki; A.I. Virtanens plats 1, P.O. Box 55 FI-00014 Helsinki Finland
| | - Ana P. Gamiz-Hernandez
- Department Chemie; Technische Universität München (TUM); Lichtenbergstrasse 4 85747 Garching Germany
| | - Ville R. I. Kaila
- Department Chemie; Technische Universität München (TUM); Lichtenbergstrasse 4 85747 Garching Germany
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45
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Guareschi R, Zulfikri H, Daday C, Floris FM, Amovilli C, Mennucci B, Filippi C. Introducing QMC/MMpol: Quantum Monte Carlo in Polarizable Force Fields for Excited States. J Chem Theory Comput 2016; 12:1674-83. [DOI: 10.1021/acs.jctc.6b00044] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Riccardo Guareschi
- MESA+
Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Habiburrahman Zulfikri
- MESA+
Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Csaba Daday
- MESA+
Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Franca Maria Floris
- Dipartimento
di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe
Moruzzi 13, 56124 Pisa, Italy
| | - Claudio Amovilli
- Dipartimento
di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe
Moruzzi 13, 56124 Pisa, Italy
| | - Benedetta Mennucci
- Dipartimento
di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe
Moruzzi 13, 56124 Pisa, Italy
| | - Claudia Filippi
- MESA+
Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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46
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Nile blue and Nile red optical properties predicted by TD-DFT and CASPT2 methods: static and dynamic solvent effects. Theor Chem Acc 2016. [DOI: 10.1007/s00214-016-1814-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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47
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Daday C, Curutchet C, Sinicropi A, Mennucci B, Filippi C. Chromophore–Protein Coupling beyond Nonpolarizable Models: Understanding Absorption in Green Fluorescent Protein. J Chem Theory Comput 2015; 11:4825-39. [DOI: 10.1021/acs.jctc.5b00650] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Csaba Daday
- MESA+
Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Carles Curutchet
- Departament
de Fisicoquı́mica, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII, s/n 08028, Barcelona, Spain
| | - Adalgisa Sinicropi
- Department
of Biotechnology, Chemistry and Pharmacy, University of Siena, Via A. Moro, 2, 53100 Siena, Italy
| | - Benedetta Mennucci
- Dipartimento
di Chimica e Chimica Industriale, Università di Pisa, Via Giuseppe
Moruzzi 3, 56124 Pisa, Italy
| | - Claudia Filippi
- MESA+
Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Chandrasekaran S, Aghtar M, Valleau S, Aspuru-Guzik A, Kleinekathöfer U. Influence of Force Fields and Quantum Chemistry Approach on Spectral Densities of BChl a in Solution and in FMO Proteins. J Phys Chem B 2015; 119:9995-10004. [DOI: 10.1021/acs.jpcb.5b03654] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
| | - Mortaza Aghtar
- Department
of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Stéphanie Valleau
- Department
of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Alán Aspuru-Guzik
- Department
of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Ulrich Kleinekathöfer
- Department
of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
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49
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Dupuy N, Bouaouli S, Mauri F, Sorella S, Casula M. Vertical and adiabatic excitations in anthracene from quantum Monte Carlo: Constrained energy minimization for structural and electronic excited-state properties in the JAGP ansatz. J Chem Phys 2015; 142:214109. [DOI: 10.1063/1.4922048] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Affiliation(s)
- Nicolas Dupuy
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Université Pierre et Marie Curie, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Samira Bouaouli
- Laboratoire de Chimie Théorique, Université Pierre et Marie Curie, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Francesco Mauri
- CNRS and Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Université Pierre et Marie Curie, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Sandro Sorella
- International School for Advanced Studies (SISSA), Via Beirut 2-4, 34014 Trieste, Italy and INFM Democritos National Simulation Center, Trieste, Italy
| | - Michele Casula
- CNRS and Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Université Pierre et Marie Curie, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France
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50
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Coughlan NJA, Catani KJ, Adamson BD, Wille U, Bieske EJ. Photoisomerization action spectrum of retinal protonated Schiff base in the gas phase. J Chem Phys 2015; 140:164307. [PMID: 24784270 DOI: 10.1063/1.4871883] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The photophysical behaviour of the isolated retinal protonated n-butylamine Schiff base (RPSB) is investigated in the gas phase using a combination of ion mobility spectrometry and laser spectroscopy. The RPSB cations are introduced by electrospray ionisation into an ion mobility mass spectrometer where they are exposed to tunable laser radiation in the region of the S1 ← S0 transition (420-680 nm range). Four peaks are observed in the arrival time distribution of the RPSB ions. On the basis of predicted collision cross sections with nitrogen gas, the dominant peak is assigned to the all-trans isomer, whereas the subsidiary peaks are assigned to various single, double and triple cis geometric isomers. RPSB ions that absorb laser radiation undergo photoisomerization, leading to a detectable change in their drift speed. By monitoring the photoisomer signal as a function of laser wavelength an action spectrum, extending from 480 to 660 nm with a clear peak at 615 ± 5 nm, is obtained. The photoisomerization action spectrum is related to the absorption spectrum of isolated retinal RPSB molecules and should help benchmark future electronic structure calculations.
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Affiliation(s)
- N J A Coughlan
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
| | - K J Catani
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
| | - B D Adamson
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
| | - U Wille
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
| | - E J Bieske
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
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