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Subramanian G, Manchanda K, Mo Y, Sathe RY, Bharatam PV. Monovalent cation binding to model systems and the macrocyclic depsipeptide, emodepside. J Comput Chem 2024. [PMID: 38924119 DOI: 10.1002/jcc.27451] [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: 03/20/2024] [Revised: 05/13/2024] [Accepted: 06/09/2024] [Indexed: 06/28/2024]
Abstract
This study focuses on the systematic exploration of the emodepside conformations bound to monovalent K+ ion using quantum mechanical density functional theory (DFT) calculations at the M06-2X/6-31+G(d,p) level of theory. Nine conformers of emodepside and their complexes with K+ ion were characterized as stationary points on the potential energy surface. The conformational isomers were examined for their 3D structures, bonding, energetics, and interactions with the cation. A cavitand-like structure (CC) is identified to be the energetically most stable arrangement. To arrive at a better understanding of the K+ ion binding, calculations were initially performed on complexes formed by the K+ and Na+ ions with model ligands (methyl ester and N,N-dimethyl acetamide). Both the natural bond orbital (NBO) method and the block-localized wavefunction (BLW) energy decomposition approach was employed to assess the bonding and energetic contributions stabilizing the ion-bound model complexes. Finally, the solvent effect was evaluated through complete geometry optimizations and energy minimizations for the model ion-ligand complexes and the emodepside-K+ bound complexes using an implicit solvent model mimicking water and DMSO.
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Affiliation(s)
| | - Kanika Manchanda
- Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S Nagar (Mohali), Punjab, India
| | - Yirong Mo
- Department of Nanoscience, Joint School of Nanoscience and Nanoengineering, University of North Carolina at Greensboro, Greensboro, North Carolina, USA
| | - Rohit Y Sathe
- Department of Biological Sciences and Biotechnology, Institute of Chemical Technology, Mumbai, Maharashtra, India
| | - Prasad V Bharatam
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S Nagar (Mohali), Punjab, India
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2
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Stevens MJ, Rempe SLB. Binding of carboxylate and water to monovalent cations. Phys Chem Chem Phys 2023; 25:29881-29893. [PMID: 37889481 DOI: 10.1039/d3cp04200f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
The interactions of carboxylate anions with water and cations are important for a wide variety of systems, both biological and synthetic. To gain insight on properties of the local complexes, we apply density functional theory, to treat the complex electrostatic interactions, and investigate mixtures with varied numbers of carboxylate anions (acetate) and waters binding to monovalent cations, Li+, Na+ and K+. The optimal structure with overall lowest free energy contains two acetates and two waters such that the cation is four-fold coordinated, similar to structures found earlier for pure water or pure carboxylate ligands. More generally, the complexes with two acetates have the lowest free energy. In transitioning from the overall optimal state, exchanging an acetate for water has a lower free energy barrier than exchanging water for an acetate. In most cases, the carboxylates are monodentate and in the first solvation shell. As water is added to the system, hydrogen bonding between waters and carboxylate O atoms further stabilizes monodentate structures. These structures, which have strong electrostatic interactions that involve hydrogen bonds of varying strength, are significantly polarized, with ChelpG partial charges that vary substantially as the bonding geometry varies. Overall, these results emphasize the increasing importance of water as a component of binding sites as the number of ligands increases, thus affecting the preferential solvation of specific metal ions and clarifying Hofmeister effects. Finally, structural analysis correlated with free energy analysis supports the idea that binding to more than the preferred number of carboxylates under architectural constraints are a key to ion transport.
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Affiliation(s)
- Mark J Stevens
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, NM 87185, USA.
| | - Susan L B Rempe
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, NM 87185, USA.
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3
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Rezaei M, Sakong S, Groß A. Molecular Modeling of Water-in-Salt Electrolytes: A Comprehensive Analysis of Polarization Effects and Force Field Parameters in Molecular Dynamics Simulations. J Chem Theory Comput 2023; 19:5712-5730. [PMID: 37528639 DOI: 10.1021/acs.jctc.3c00171] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023]
Abstract
Accurate modeling of highly concentrated aqueous solutions, such as water-in-salt (WiS) electrolytes in battery applications, requires proper consideration of polarization contributions to atomic interactions. Within the force field molecular dynamics (MD) simulations, the atomic polarization can be accounted for at various levels. Nonpolarizable force fields implicitly account for polarization effects by incorporating them into their van der Waals interaction parameters. They can additionally mimic electron polarization within a mean-field approximation through ionic charge scaling. Alternatively, explicit polarization description methods, such as the Drude oscillator model, can be selectively applied to either a subset of polarizable atoms or all polarizable atoms to enhance simulation accuracy. The trade-off between simulation accuracy and computational efficiency highlights the importance of determining an optimal level of accounting for atomic polarization. In this study, we analyze different approaches to include polarization effects in MD simulations of WiS electrolytes, with an example of a Na-OTF solution. These approaches range from a nonpolarizable to a fully polarizable force field. After careful examination of computational costs, simulation stability, and feasibility of controlling the electrolyte properties, we identify an efficient combination of force fields: the Drude polarizable force field for salt ions and non-polarizable models for water. This cost-effective combination is sufficiently flexible to reproduce a broad range of electrolyte properties, while ensuring simulation stability over a relatively wide range of force field parameters. Furthermore, we conduct a thorough evaluation of the influence of various force field parameters on both the simulation results and technical requirements, with the aim of establishing a general framework for force field optimization and facilitating parametrization of similar systems.
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Affiliation(s)
- Majid Rezaei
- Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany
| | - Sung Sakong
- Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany
| | - Axel Groß
- Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany
- Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage, Helmholtzstraße 11, 89069 Ulm, Germany
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4
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Kudaibergenova M, Guo J, Khan HM, Lees-Miller J, Mousaei M, Miranda W, Ngo VA, Noskov SY, Tieleman DP, Duff HJ. The voltage-sensing domain of a hERG1 mutant is a cation-selective channel. Biophys J 2022; 121:4585-4599. [PMID: 36815709 PMCID: PMC9748372 DOI: 10.1016/j.bpj.2022.10.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 06/29/2022] [Accepted: 10/24/2022] [Indexed: 11/24/2022] Open
Abstract
A cationic leak current known as an "omega current" may arise from mutations of the first charged residue in the S4 of the voltage sensor domains of sodium and potassium voltage-gated channels. The voltage-sensing domains (VSDs) in these mutated channels act as pores allowing nonspecific passage of cations, such as Li+, K+, Cs+, and guanidinium. Interestingly, no omega currents have been previously detected in the nonswapped voltage-gated potassium channels such as the human-ether-a-go-go-related (hERG1), hyperpolarization-activated cyclic nucleotide-gated, and ether-a-go-go channels. In this work, we discovered a novel omega current by mutating the first charged residue of the S4 of the hERG1, K525 to serine. To characterize this omega current, we used various probes, including the hERG1 pore domain blocker, dofetilide, to show that the omega current does not require cation flux via the canonical pore domain. In addition, the omega flux does not cross the conventional selectivity filter. We also show that the mutated channel (K525S hERG1) conducts guanidinium. These data are indicative of the formation of an omega current channel within the VSD. Using molecular dynamics simulations with replica-exchange umbrella sampling simulations of the wild-type hERG1 and the K525S hERG1, we explored the molecular underpinnings governing the cation flow in the VSD of the mutant. We also show that the wild-type hERG1 may form water crevices supported by the biophysical surface accessibility data. Overall, our multidisciplinary study demonstrates that the VSD of hERG1 may act as a cation-selective channel wherein a mutation of the first charged residue in the S4 generates an omega current. Our simulation uncovers the atomistic underpinning of this mechanism.
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Affiliation(s)
- Meruyert Kudaibergenova
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Jiqing Guo
- Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - Hanif M Khan
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - James Lees-Miller
- Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - Mahdi Mousaei
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Williams Miranda
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Van A Ngo
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Sergei Yu Noskov
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences, University of Calgary, Calgary, AB, Canada.
| | - Henry J Duff
- Department of Cardiac Sciences, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada.
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5
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Zhuang D, Riera M, Zhou R, Deary A, Paesani F. Hydration Structure of Na + and K + Ions in Solution Predicted by Data-Driven Many-Body Potentials. J Phys Chem B 2022; 126:9349-9360. [PMID: 36326071 DOI: 10.1021/acs.jpcb.2c05674] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The hydration structure of Na+ and K+ ions in solution is systematically investigated using a hierarchy of molecular models that progressively include more accurate representations of many-body interactions. We found that a conventional empirical pairwise additive force field that is commonly used in biomolecular simulations is unable to reproduce the extended X-ray absorption fine structure (EXAFS) spectra for both ions. In contrast, progressive inclusion of many-body effects rigorously derived from the many-body expansion of the energy allows the MB-nrg potential energy functions (PEFs) to achieve nearly quantitative agreement with the experimental EXAFS spectra, thus enabling the development of a molecular-level picture of the hydration structure of both Na+ and K+ in solution. Since the MB-nrg PEFs have already been shown to accurately describe isomeric equilibria and vibrational spectra of small ion-water clusters in the gas phase, the present study demonstrates that the MB-nrg PEFs effectively represent the long-sought-after models able to correctly predict the properties of ionic aqueous systems from the gas to the liquid phase, which has so far remained elusive.
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Affiliation(s)
- Debbie Zhuang
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California92093, United States
| | - Marc Riera
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California92093, United States
| | - Ruihan Zhou
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California92093, United States
| | - Alexander Deary
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California92093, United States
| | - Francesco Paesani
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California92093, United States.,Materials Science and Engineering, University of California San Diego, La Jolla, California92093, United States.,San Diego Supercomputer Center, University of California San Diego, La Jolla, California92093, United States
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6
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Delgado JA, Wineman-Fisher V, Pandit S, Varma S. Inclusion of High-Field Target Data in AMOEBA's Calibration Improves Predictions of Protein-Ion Interactions. J Chem Inf Model 2022; 62:4713-4726. [PMID: 36173398 DOI: 10.1021/acs.jcim.2c00758] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The reliability of molecular mechanics simulations to predict effects of ion binding to proteins depends on their ability to simultaneously describe ion-protein, ion-water, and protein-water interactions. Force fields (FFs) to describe protein-water and ion-water interactions have been constructed carefully and have also been refined routinely to improve accuracy. Descriptions for ion-protein interactions have also been refined, although in an a posteriori manner through the use of "nonbonded-fix (NB-fix)" approaches in which parameters from default Lennard-Jones mixing rules are replaced with those optimized against some reference data. However, even after NB-fix corrections, there remains a significant need for improvement. This is also true for polarizable FFs that include self-consistent inducible moments. Our recent studies on the polarizable AMOEBA FF suggested that the problem associated with modeling ion-protein interactions could be alleviated by recalibrating polarization models of cation-coordinating functional groups so that they respond better to the high electric fields present near ions. Here, we present such a recalibration of carbonyls, carboxylates, and hydroxyls in the AMOEBA protein FF and report that it does improve predictions substantially─mean absolute errors in Na+-protein and K+-protein interaction energies decrease from 8.7 to 5.3 and 9.6 to 6.3 kcal/mol, respectively. Errors are computed with respect to estimates from van der Waals-inclusive density functional theory benchmarked against high-level quantum mechanical calculations and experiments. While recalibration does improve ion-protein interaction energies, they still remain underestimated, suggesting that further improvements can be made in a systematic manner through modifications in classical formalism. Nevertheless, we show that by applying our many-body NB-fix correction to Lennard-Jones components, these errors are further reduced to 2.7 and 2.6 kcal/mol, respectively, for Na+ and K+ ions. Finally, we show that the recalibrated AMOEBA protein FF retains its intrinsic reliability in predicting protein structure and dynamics in the condensed phase.
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Affiliation(s)
- Julián A Delgado
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States
| | - Vered Wineman-Fisher
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States
| | - Sagar Pandit
- Department of Physics, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States
| | - Sameer Varma
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States.,Department of Physics, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, United States
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7
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Kumar A, Pandey P, Chatterjee P, MacKerell AD. Deep Neural Network Model to Predict the Electrostatic Parameters in the Polarizable Classical Drude Oscillator Force Field. J Chem Theory Comput 2022; 18:1711-1725. [PMID: 35148088 PMCID: PMC8904317 DOI: 10.1021/acs.jctc.1c01166] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The Drude polarizable force field (FF) captures electronic polarization effects via auxiliary Drude particles that are attached to non-hydrogen atoms, distinguishing it from commonly used additive FFs that rely on fixed charges. The Drude FF currently includes parameters for biomolecules such as proteins, nucleic acids, lipids, and carbohydrates and small-molecule representative of those classes of molecules as well as a range of atomic ions. Extension of the Drude FF to novel small druglike molecules is challenging as it requires the assignment of partial charges, atomic polarizabilities, and Thole scaling factors. In the present article, deep neural network (DNN) models are trained on quantum mechanical (QM)-based partial charges and atomic polarizabilities along with Thole scale factors trained to target QM molecular dipole moments and polarizabilities. Training of the DNN model used a collection of 39 421 molecules with molecular weights up to 200 Da and containing H, C, N, O, P, S, F, Cl, Br, or I atoms. The DNN model utilizes bond connectivity, including 1,2, 1,3, 1,4, and 1,5 terms and distances of Drude FF atom types as the feature vector to build the model, allowing it to capture both local and nonlocal effects in the molecules. Novel methods have been developed to determine restrained electrostatic potential (RESP) charges on atoms and external points representing lone pairs and to determine Thole scale factors, which have no QM analogue. A penalty scheme is devised as a performance predictor of the trained model. Validation studies show that these DNN models can precisely predict molecular dipole and polarizabilities of Food and Drug Administration (FDA)-approved drugs compared to reference MP2 calculations. The availability of the DNN model allowing for the rapid estimation of the Drude electrostatic parameters will facilitate its applicability to a wider range of molecular species.
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Affiliation(s)
- Anmol Kumar
- School of Pharmacy, University of Maryland, Baltimore, 20 Penn Street, HSFII, Baltimore, Maryland 21201, United States
| | - Poonam Pandey
- School of Pharmacy, University of Maryland, Baltimore, 20 Penn Street, HSFII, Baltimore, Maryland 21201, United States
| | - Payal Chatterjee
- School of Pharmacy, University of Maryland, Baltimore, 20 Penn Street, HSFII, Baltimore, Maryland 21201, United States
| | - Alexander D MacKerell
- School of Pharmacy, University of Maryland, Baltimore, 20 Penn Street, HSFII, Baltimore, Maryland 21201, United States
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8
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Priest CW, Greathouse JA, Kinnan MK, Burton PD, Rempe SB. Ab initio and force field molecular dynamics study of bulk organophosphorus and organochlorine liquid structures. J Chem Phys 2021; 154:084503. [PMID: 33639727 DOI: 10.1063/5.0033426] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We performed ab initio molecular dynamics (AIMD) simulations to benchmark bulk liquid structures and to evaluate results from all-atom force field molecular dynamics (FFMD) simulations with the generalized Amber force field (GAFF) for organophosphorus (OP) and organochlorine (OC) compounds. Our work also addresses the current and important topic of force field validation, applied here to a set of nonaqueous organic liquids. Our approach differs from standard treatments, which validate force fields based on thermodynamic data. Utilizing radial distribution functions (RDFs), our results show that GAFF reproduces the AIMD-predicted asymmetric liquid structures moderately well for OP compounds that contain bulky alkyl groups. Among the OCs, RDFs obtained from FFMD overlap well with AIMD results, with some offsets in position and peak structuring. However, re-parameterization of GAFF for some OCs is needed to reproduce fully the liquid structures predicted by AIMD. The offsets between AIMD and FFMD peak positions suggest inconsistencies in the developed force fields, but, in general, GAFF is able to capture short-ranged and long-ranged interactions of OPs and OCs observed in AIMD. Along with the local coordination structure, we also compared enthalpies of vaporization. Overall, calculated bulk properties from FFMD compared reasonably well with experimental values, suggesting that small improvements within the FF should focus on parameters that adjust the bulk liquid structures of these compounds.
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Affiliation(s)
- Chad W Priest
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | | | - Mark K Kinnan
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Patrick D Burton
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Susan B Rempe
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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9
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Wineman-Fisher V, Al-Hamdani Y, Nagy PR, Tkatchenko A, Varma S. Improved description of ligand polarization enhances transferability of ion-ligand interactions. J Chem Phys 2020; 153:094115. [PMID: 32891085 PMCID: PMC9812517 DOI: 10.1063/5.0022058] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The reliability of molecular mechanics (MM) simulations in describing biomolecular ion-driven processes depends on their ability to accurately model interactions of ions simultaneously with water and other biochemical groups. In these models, ion descriptors are calibrated against reference data on ion-water interactions, and it is then assumed that these descriptors will also satisfactorily describe interactions of ions with other biochemical ligands. The comparison against the experiment and high-level quantum mechanical data show that this transferability assumption can break down severely. One approach to improve transferability is to assign cross terms or separate sets of non-bonded descriptors for every distinct pair of ion type and its coordinating ligand. Here, we propose an alternative solution that targets an error-source directly and corrects misrepresented physics. In standard model development, ligand descriptors are never calibrated or benchmarked in the high electric fields present near ions. We demonstrate for a representative MM model that when the polarization descriptors of its ligands are improved to respond to both low and high fields, ligand interactions with ions also improve, and transferability errors reduce substantially. In our case, the overall transferability error reduces from 3.3 kcal/mol to 1.8 kcal/mol. These improvements are observed without compromising on the accuracy of low-field interactions of ligands in gas and condensed phases. Reference data for calibration and performance evaluation are taken from the experiment and also obtained systematically from "gold-standard" CCSD(T) in the complete basis set limit, followed by benchmarked vdW-inclusive density functional theory.
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Affiliation(s)
- Vered Wineman-Fisher
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida 33620, USA
| | - Yasmine Al-Hamdani
- Physics and Materials Science Research Unit, University of Luxembourg, 162a Avenue de La Fïancerie, Luxembourg City L-1511, Luxembourg
| | - Péter R. Nagy
- Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, P. O. Box 91, H-1521 Budapest, Hungary
| | - Alexandre Tkatchenko
- Physics and Materials Science Research Unit, University of Luxembourg, 162a Avenue de La Fïancerie, Luxembourg City L-1511, Luxembourg
| | - Sameer Varma
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida 33620, USA,Author to whom correspondence should be addressed:
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10
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Krämer A, Hudson PS, Jones MR, Brooks BR. Multi-phase Boltzmann weighting: accounting for local inhomogeneity in molecular simulations of water-octanol partition coefficients in the SAMPL6 challenge. J Comput Aided Mol Des 2020; 34:471-483. [PMID: 32060677 PMCID: PMC8750956 DOI: 10.1007/s10822-020-00285-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 01/08/2020] [Indexed: 02/08/2023]
Abstract
Accurately computing partition coefficients is a pivotal part of drug discovery. Specifically, octanol-water partition coefficients can provide information into hydrophobicity of drug-like molecules, as well as a de facto representation of membrane permeability. However, one challenge facing the computation of partition coefficients is the need to encapsulate various microscopic environments. These include areas of largely bulk solvent (i.e., either water or octanol) or regions where octanol is saturated with water or areas of higher salt concentration. Also, tautomeric effects require consideration. Thus, we present a Boltzmann weighting approach that incorporates transfer free energies across varying microscopic media, as well as varying tautomeric state, to compute partition coefficients in the SAMPL6 challenge.
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Affiliation(s)
- Andreas Krämer
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Phillip S Hudson
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- Department of Chemistry, University of South Florida, Tampa, FL, 33620, USA
| | - Michael R Jones
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Bernard R Brooks
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA
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11
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Chaudhari MI, Vanegas JM, Pratt LR, Muralidharan A, Rempe SB. Hydration Mimicry by Membrane Ion Channels. Annu Rev Phys Chem 2020; 71:461-484. [PMID: 32155383 DOI: 10.1146/annurev-physchem-012320-015457] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ions transiting biomembranes might pass readily from water through ion-specific membrane proteins if these protein channels provide environments similar to the aqueous solution hydration environment. Indeed, bulk aqueous solution is an important reference condition for the ion permeation process. Assessment of this hydration mimicry concept depends on understanding the hydration structure and free energies of metal ions in water in order to provide a comparison for the membrane channel environment. To refine these considerations, we review local hydration structures of ions in bulk water and the molecular quasi-chemical theory that provides hydration free energies. In doing so, we note some current views of ion binding to membrane channels and suggest new physical chemical calculations and experiments that might further clarify the hydration mimicry concept.
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Affiliation(s)
- Mangesh I Chaudhari
- Department of Computational Biology and Biophysics, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA;
| | - Juan M Vanegas
- Department of Computational Biology and Biophysics, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA; .,Current affiliation: Department of Physics, University of Vermont, Burlington, Vermont 05405, USA
| | - L R Pratt
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, USA
| | - Ajay Muralidharan
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, USA.,Current affiliation: Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - Susan B Rempe
- Department of Computational Biology and Biophysics, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA;
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12
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Cryo-EM structures of a lipid-sensitive pentameric ligand-gated ion channel embedded in a phosphatidylcholine-only bilayer. Proc Natl Acad Sci U S A 2020; 117:1788-1798. [PMID: 31911476 PMCID: PMC6983364 DOI: 10.1073/pnas.1906823117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The lipid dependence of the nicotinic acetylcholine receptor from the Torpedo electric organ has long been recognized, and one of the most consistent experimental observations is that, when reconstituted in membranes formed by zwitterionic phospholipids alone, exposure to agonist fails to elicit ion-flux activity. More recently, it has been suggested that the bacterial homolog ELIC (Erwinia chrysanthemi ligand-gated ion channel) has a similar lipid sensitivity. As a first step toward the elucidation of the structural basis of this phenomenon, we solved the structures of ELIC embedded in palmitoyl-oleoyl-phosphatidylcholine- (POPC-) only nanodiscs in both the unliganded (4.1-Å resolution) and agonist-bound (3.3 Å) states using single-particle cryoelectron microscopy. Comparison of the two structural models revealed that the largest differences occur at the level of loop C-at the agonist-binding sites-and the loops at the interface between the extracellular and transmembrane domains (ECD and TMD, respectively). On the other hand, the transmembrane pore is occluded in a remarkably similar manner in both structures. A straightforward interpretation of these findings is that POPC-only membranes frustrate the ECD-TMD coupling in such a way that the "conformational wave" of liganded-receptor gating takes place in the ECD and the interfacial M2-M3 linker but fails to penetrate the membrane and propagate into the TMD. Furthermore, analysis of the structural models and molecular simulations suggested that the higher affinity for agonists characteristic of the open- and desensitized-channel conformations results, at least in part, from the tighter confinement of the ligand to its binding site; this limits the ligand's fluctuations, and thus delays its escape into bulk solvent.
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13
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Flood E, Boiteux C, Lev B, Vorobyov I, Allen TW. Atomistic Simulations of Membrane Ion Channel Conduction, Gating, and Modulation. Chem Rev 2019; 119:7737-7832. [DOI: 10.1021/acs.chemrev.8b00630] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Emelie Flood
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Céline Boiteux
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Bogdan Lev
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Igor Vorobyov
- Department of Physiology & Membrane Biology/Department of Pharmacology, University of California, Davis, 95616, United States
| | - Toby W. Allen
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
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14
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Wineman-Fisher V, Al-Hamdani Y, Addou I, Tkatchenko A, Varma S. Ion-Hydroxyl Interactions: From High-Level Quantum Benchmarks to Transferable Polarizable Force Fields. J Chem Theory Comput 2019; 15:2444-2453. [PMID: 30830778 PMCID: PMC6598712 DOI: 10.1021/acs.jctc.8b01198] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Ion descriptors in molecular mechanics models are calibrated against reference data on ion-water interactions. It is then typically assumed that these descriptors will also satisfactorily describe interactions of ions with other functional groups, such as those present in biomolecules. However, several studies now demonstrate that this transferability assumption produces, in many different cases, large errors. Here we address this issue in a representative polarizable model and focus on transferability of cationic interactions from water to a series of alcohols. Both water and alcohols use hydroxyls for ion-coordination, and, therefore, this set of molecules constitutes the simplest possible case of transferability. We obtain gas phase reference data systematically from "gold-standard" quantum Monte Carlo and CCSD(T) methods, followed by benchmarked vdW-corrected DFT. We learn that the original polarizable model yields large gas phase water → alcohol transferability errors - the RMS and maximum errors are 2.3 and 5.1 kcal/mol, respectively. These errors are, nevertheless, systematic in that ion-alcohol interactions are overstabilized, and systematic errors typically imply that some essential physics is either missing or misrepresented. A comprehensive analysis shows that when both low- and high-field responses of ligand dipole polarization are described accurately, then transferability improves significantly - the RMS and maximum errors in the gas phase reduce, respectively, to 0.9 and 2.5 kcal/mol. Additionally, predictions of condensed phase transfer free energies also improve. Nevertheless, within the limits of the extrathermodynamic assumptions necessary to separate experimental estimates of salt dissolution into constituent cationic and anionic contributions, we note that the error in the condensed phase is systematic, which we attribute, at least, partially to the parametrization in long-range electrostatics. Overall, this work demonstrates a rational approach to boosting transferability of ionic interactions that will be applicable broadly to improving other polarizable and nonpolarizable models.
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Affiliation(s)
- Vered Wineman-Fisher
- Department of Cell Biology, Microbiology and Molecular Biology , University of South Florida , Tampa , Florida 33620 , United States
| | - Yasmine Al-Hamdani
- Physics and Materials Science Research Unit , University of Luxembourg , 162a avenue de la Fïancerie , Luxembourg City , L-1511 , Luxembourg
| | - Iqbal Addou
- Department of Cell Biology, Microbiology and Molecular Biology , University of South Florida , Tampa , Florida 33620 , United States
| | - Alexandre Tkatchenko
- Physics and Materials Science Research Unit , University of Luxembourg , 162a avenue de la Fïancerie , Luxembourg City , L-1511 , Luxembourg
| | - Sameer Varma
- Department of Cell Biology, Microbiology and Molecular Biology , University of South Florida , Tampa , Florida 33620 , United States
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15
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Prasetyo N, Hünenberger PH, Hofer TS. Single-Ion Thermodynamics from First Principles: Calculation of the Absolute Hydration Free Energy and Single-Electrode Potential of Aqueous Li + Using ab Initio Quantum Mechanical/Molecular Mechanical Molecular Dynamics Simulations. J Chem Theory Comput 2018; 14:6443-6459. [PMID: 30284829 DOI: 10.1021/acs.jctc.8b00729] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A recently proposed thermodynamic integration (TI) approach formulated in the framework of quantum mechanical/molecular mechanical molecular dynamics (QM/MM MD) simulations is applied to study the structure, dynamics, and absolute intrinsic hydration free energy Δs GM+,wat◦ of the Li+ ion at a correlated ab initio level of theory. Based on the results, standard values (298.15 K, ideal gas at 1 bar, ideal solute at 1 molal) for the absolute intrinsic hydration free energy [Formula: see text] of the proton, the surface electric potential jump χwat◦ upon entering bulk water, and the absolute single-electrode potential [Formula: see text] of the reference hydrogen electrode are calculated to be -1099.9 ± 4.2 kJ·mol-1, 0.13 ± 0.08 V, and 4.28 ± 0.04 V, respectively, in excellent agreement with the standard values recommended by Hünenberger and Reif on the basis of an extensive evaluation of the available experimental data (-1100 ± 5 kJ·mol-1, 0.13 ± 0.10 V, and 4.28 ± 0.13 V). The simulation results for Li+ are also compared to those for Na+ and K+ from a previous study in terms of relative hydration free energies ΔΔs GM+,wat◦ and relative electrode potentials [Formula: see text]. The calculated values are found to agree extremely well with the experimental differences in standard conventional hydration free energies ΔΔs GM+,wat• and redox potentials [Formula: see text]. The level of agreement between simulation and experiment, which is quantitative within error bars, underlines the substantial accuracy improvement achieved by applying a highly demanding QM/MM approach at the resolution-of-identity second-order Møller-Plesset perturbation (RIMP2) level over calculations relying on purely molecular mechanical or density functional theory (DFT) descriptions. A detailed analysis of the structural and dynamical properties of the Li+ hydrate indicates that a correct description of the solvation structure and dynamics is achieved as well at this level of theory. Consideration of the QM/MM potential-energy components also shows that the partitioning into QM and MM zones does not induce any significant energetic artifact for the system considered.
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Affiliation(s)
- Niko Prasetyo
- Theoretical Chemistry Division, Institute of General, Inorganic and Theoretical Chemistry , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria.,Austria-Indonesia Centre (AIC) for Computational Chemistry , Universitas Gadjah Mada , Sekip Utara , Yogyakarta 55281 , Indonesia.,Department of Chemistry, Faculty of Mathematics and Natural Sciences , Universitas Gadjah Mada , Sekip Utara , Yogyakarta 55281 , Indonesia
| | - Philippe H Hünenberger
- Laboratorium für Physikalische Chemie , ETH Zürich, ETH-Hönggerberg , HCI Building , CH-8093 Zürich , Switzerland
| | - Thomas S Hofer
- Theoretical Chemistry Division, Institute of General, Inorganic and Theoretical Chemistry , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria
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16
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Awoonor-Williams E, Rowley CN. The hydration structure of methylthiolate from QM/MM molecular dynamics. J Chem Phys 2018; 149:045103. [PMID: 30068187 DOI: 10.1063/1.5038010] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Thiols are widely present in biological systems, most notably as the side chain of cysteine amino acids in proteins. Thiols can be deprotonated to form a thiolate which affords a diverse range of enzymatic activity and modes for chemical modification of proteins. Parameters for modeling thiolates using molecular mechanical force fields have not yet been validated, in part due to the lack of structural data on thiolate solvation. Here, the CHARMM36 and Amber models for thiolates in aqueous solutions are assessed using free energy perturbation and hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations. The hydration structure of methylthiolate was calculated from 1 ns of QM/MM MD (PBE0-D3/def2-TZVP//TIP3P), which shows that the water-S- distances are approximately 2 Å with a coordination number near 6. The CHARMM thiolate parameters predict a thiolate S radius close to the QM/MM value and predict a hydration Gibbs energy of -329.2 kJ/mol, close to the experimental value of -318 kJ/mol. The cysteine thiolate model in the Amber force field underestimates the thiolate radius by 0.2 Å and overestimates the thiolate hydration energy by 119 kJ/mol because it uses the same Lennard-Jones parameters for thiolates as for thiols. A recent Drude polarizable model for methylthiolate with optimized thiolate parameters also performs well. SAPT2+ [Symmetry Adapted Perturbation Theory (SAPT)] analysis indicates that exchange repulsion is larger for the methylthiolate, consistent with it having a more diffuse electron density distribution in comparison with the parent thiol. These data demonstrate that it is important to define distinct non-bonded parameters for the protonated/deprotonated states of amino acid side chains in molecular mechanical force fields.
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Affiliation(s)
- Ernest Awoonor-Williams
- Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador A1C 5S7, Canada
| | - Christopher N Rowley
- Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador A1C 5S7, Canada
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17
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Hofer TS, Hünenberger PH. Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration. J Chem Phys 2018; 148:222814. [DOI: 10.1063/1.5000799] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Thomas S. Hofer
- Theoretical Chemistry Division, Institute of General, Inorganic and Theoretical Chemistry, Centre for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
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18
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Revisiting structure and dynamics of preferential solvation of K(I) ion in aqueous ammonia using QMCF-MD simulation. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2018.03.067] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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19
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Awoonor-Williams E, Rowley CN. The hydration structure of carbon monoxide byab initiomethods. J Chem Phys 2017; 146:034503. [DOI: 10.1063/1.4974164] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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20
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Silva NM, Deglmann P, Pliego JR. CMIRS Solvation Model for Methanol: Parametrization, Testing, and Comparison with SMD, SM8, and COSMO-RS. J Phys Chem B 2016; 120:12660-12668. [DOI: 10.1021/acs.jpcb.6b10249] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Natalia M. Silva
- Departamento
de Ciências Naturais, Universidade Federal de São João del-Rei, 36301-160 São João
del-Rei, Minas Gerais, Brazil
| | - Peter Deglmann
- Polymer Processing & Engineering, BASF SE, Carl-Bosch-Str. 38, 67056 Ludwigshafen, Germany
| | - Josefredo R. Pliego
- Departamento
de Ciências Naturais, Universidade Federal de São João del-Rei, 36301-160 São João
del-Rei, Minas Gerais, Brazil
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21
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Li RZ, Zeng Z, Hou GL, Xu HG, Zhao X, Gao YQ, Zheng WJ. Hydration of potassium iodide dimer studied by photoelectron spectroscopy and ab initio calculations. J Chem Phys 2016; 145:184307. [DOI: 10.1063/1.4967168] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ren-Zhong Li
- Institute for Chemical Physics, School of Science, Xi’an Jiaotong University, Xi’an 710049, China
- College of Electronics and Information, Xi’an Polytechnic University, Xi’an 710048, China
| | - Zhen Zeng
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Gao-Lei Hou
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hong-Guang Xu
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiang Zhao
- Institute for Chemical Physics, School of Science, Xi’an Jiaotong University, Xi’an 710049, China
| | - Yi Qin Gao
- Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wei-Jun Zheng
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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22
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Sadhu B, Sundararajan M, Bandyopadhyay T. Selectivity of a Singly Permeating Ion in Nonselective NaK Channel: Combined QM and MD Based Investigations. J Phys Chem B 2015; 119:12783-97. [DOI: 10.1021/acs.jpcb.5b05996] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Biswajit Sadhu
- Radiation Safety Systems Division and ‡Theoretical Chemistry
Section, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - Mahesh Sundararajan
- Radiation Safety Systems Division and ‡Theoretical Chemistry
Section, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - Tusar Bandyopadhyay
- Radiation Safety Systems Division and ‡Theoretical Chemistry
Section, Bhabha Atomic Research Centre, Mumbai 400 085, India
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23
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Abstract
The hydration structure of Ba(2+) ion is important for understanding blocking mechanisms in potassium ion channels. Here, we combine statistical mechanical theory, ab initio molecular dynamics simulations, and electronic structure methods to calculate the hydration free energy and local hydration structure of Ba(2+)(aq). The predicted hydration free energy (-304 ± 1 kcal/mol) agrees with the experimental value (-303 kcal/mol) when a maximally occupied, unimodal inner solvation shell is treated. In the local environment defined by the first shell of hydrating waters, Ba(2+) is directly and stably coordinated by eight (8) waters. Octa-coordination resembles the crystal structure of Ba(2+) and K(+) bound in potassium ion channels, but differs from the local hydration structure of K(+)(aq) determined earlier.
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Affiliation(s)
- Mangesh I Chaudhari
- †Center for Biological and Engineering Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Marielle Soniat
- ‡Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, United States
| | - Susan B Rempe
- †Center for Biological and Engineering Sciences, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
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24
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Shi Y, Ren P, Schnieders M, Piquemal JP. Polarizable Force Fields for Biomolecular Modeling. REVIEWS IN COMPUTATIONAL CHEMISTRY 2015. [DOI: 10.1002/9781118889886.ch2] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Ke H, van der Linde C, Lisy JM. Insights into the Structures of the Gas-Phase Hydrated Cations M+(H2O)nAr (M = Li, Na, K, Rb, and Cs; n = 3–5) Using Infrared Photodissociation Spectroscopy and Thermodynamic Analysis. J Phys Chem A 2015; 119:2037-51. [DOI: 10.1021/jp509694h] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Haochen Ke
- Department of Chemistry, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Christian van der Linde
- Department of Chemistry, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - James M. Lisy
- Department of Chemistry, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
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26
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Riahi S, Rowley CN. The CHARMM-TURBOMOLE interface for efficient and accurate QM/MM molecular dynamics, free energies, and excited state properties. J Comput Chem 2014; 35:2076-86. [PMID: 25178266 DOI: 10.1002/jcc.23716] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Revised: 08/04/2014] [Accepted: 08/07/2014] [Indexed: 01/05/2023]
Abstract
The quantum mechanical (QM)/molecular mechanical (MM) interface between Chemistry at HARvard Molecular Mechanics (CHARMM) and TURBOMOLE is described. CHARMM provides an extensive set of simulation algorithms, like molecular dynamics (MD) and free energy perturbation, and support for mature nonpolarizable and Drude polarizable force fields. TURBOMOLE provides fast QM calculations using density functional theory or wave function methods and excited state properties. CHARMM-TURBOMOLE is well-suited for extended QM/MM MD simulations using first principles methods with large (triple-ζ) basis sets. We demonstrate these capabilities with a QM/MM simulation of Mg(2+) (aq), where the MM outer sphere water molecules are represented using the SWM4-NDP Drude polarizable force field and the ion and inner coordination sphere are represented using QM PBE, PBE0, and MP2 methods. The relative solvation free energies of Mg(2+) and Zn(2+) were calculated using thermodynamic integration. We also demonstrate the features for excited state properties. We calculate the time-averaged solution absorption spectrum of indole, the emission spectrum of the indole 1La excited state, and the electronic circular dichroism spectrum of an oxacepham.
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Affiliation(s)
- Saleh Riahi
- Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X7, Canada
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27
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Mitev PD, Bakó I, Eriksson A, Hermansson K. Large polarization but small electron transfer for water around Al(3+) in a highly hydrated crystal. Phys Chem Chem Phys 2014; 16:9351-63. [PMID: 24718484 DOI: 10.1039/c3cp55358b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Precise molecular-level information on the water molecule is precious, since it affects our interpretation of the role of water in a range of important applications of aqueous media. Here we propose that electronic structure calculations for highly hydrated crystals yield such information. Properties of nine structurally different water molecules (19 independent OO hydrogen bonds) in the Al(NO3)3·9H2O crystal have been calculated from DFT calculations. We combine the advantage of studying different water environments using one and the same compound and method (instead of comparing a set of independent experiments, each with its own set of errors) with the advantage of knowing the exact atomic positions, and the advantage of calculating properties that are difficult to extract from experiment. We find very large Wannier dipole moments for H2O molecules surrounding the cations: 4.0-4.3 D (compared to our calculated value of 1.83 D in the gas phase). These are induced by the ions and the H-bonds, while other water interactions and the relaxation of the internal water geometry in fact decrease the dipole moments. We find a good correlation between the water dipole moment and the OO distances, and an even better (non-linear) correlation with the average electric field over the molecule. Literature simulation data for ionic aqueous solutions fit quite well with our crystalline 'dipole moment vs. OO distance' curve. The progression of the water and cation charges from 'small clusters ⇒ large clusters ⇒ the crystal' helps explain why the net charges on all the water molecules are so small in the crystal.
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Affiliation(s)
- Pavlin D Mitev
- Department of Chemistry, The Ångström Laboratory, Uppsala University, Box 538, S-751 21 Uppsala, Sweden.
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28
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Debiec KT, Gronenborn AM, Chong LT. Evaluating the strength of salt bridges: a comparison of current biomolecular force fields. J Phys Chem B 2014; 118:6561-9. [PMID: 24702709 PMCID: PMC4064690 DOI: 10.1021/jp500958r] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
![]()
Recent advances in computer hardware
and software have made rigorous
evaluation of current biomolecular force fields using microsecond-scale
simulations possible. Force fields differ in their treatment of electrostatic
interactions, including the formation of salt bridges in proteins.
Here we conducted an extensive evaluation of salt bridge interactions
in the latest AMBER, CHARMM, and OPLS force fields, using microsecond-scale
molecular dynamics simulations of amino acid analogues in explicit
solvent. We focused on salt bridges between three different pairs
of oppositely charged amino acids: Arg/Asp, Lys/Asp, and His(+)/Asp.
Our results reveal considerable variability in the predicted KA values of the salt bridges for these force
fields, as well as differences from experimental data: almost all
of the force fields overestimate the strengths of the salt bridges.
When amino acids are represented by side-chain analogues, the AMBER
ff03 force field overestimates the KA values
the least, while for complete amino acids, the AMBER ff13α force
field yields the lowest KA value, most
likely caused by an altered balance of side-chain/side-chain and side-chain/backbone
contacts. These findings confirm the notion that the implicit incorporation
of solvent polarization improves the accuracy of modeling salt bridge
interactions.
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Affiliation(s)
- Karl T Debiec
- Molecular Biophysics and Structural Biology Graduate Program, University of Pittsburgh and Carnegie Mellon University , Pittsburgh, Pennsylvania 15260/15213, United States
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29
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Bankura A, Carnevale V, Klein ML. Hydration structure of Na+and K+fromab initiomolecular dynamics based on modern density functional theory. Mol Phys 2014. [DOI: 10.1080/00268976.2014.905721] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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30
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Analysis of fast boundary-integral approximations for modeling electrostatic contributions of molecular binding. MOLECULAR BASED MATHEMATICAL BIOLOGY 2014; 1:124-150. [PMID: 24466561 DOI: 10.2478/mlbmb-2013-0007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We analyze and suggest improvements to a recently developed approximate continuum-electrostatic model for proteins. The model, called BIBEE/I (boundary-integral based electrostatics estimation with interpolation), was able to estimate electrostatic solvation free energies to within a mean unsigned error of 4% on a test set of more than 600 proteins-a significant improvement over previous BIBEE models. In this work, we tested the BIBEE/I model for its capability to predict residue-by-residue interactions in protein-protein binding, using the widely studied model system of trypsin and bovine pancreatic trypsin inhibitor (BPTI). Finding that the BIBEE/I model performs surprisingly less well in this task than simpler BIBEE models, we seek to explain this behavior in terms of the models' differing spectral approximations of the exact boundary-integral operator. Calculations of analytically solvable systems (spheres and tri-axial ellipsoids) suggest two possibilities for improvement. The first is a modified BIBEE/I approach that captures the asymptotic eigenvalue limit correctly, and the second involves the dipole and quadrupole modes for ellipsoidal approximations of protein geometries. Our analysis suggests that fast, rigorous approximate models derived from reduced-basis approximation of boundary-integral equations might reach unprecedented accuracy, if the dipole and quadrupole modes can be captured quickly for general shapes.
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31
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Cisneros GA, Karttunen M, Ren P, Sagui C. Classical electrostatics for biomolecular simulations. Chem Rev 2014; 114:779-814. [PMID: 23981057 PMCID: PMC3947274 DOI: 10.1021/cr300461d] [Citation(s) in RCA: 192] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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32
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Shiga M, Masia M. Boundary based on exchange symmetry theory for multilevel simulations. II. Multiple time scale approach. J Chem Phys 2013; 139:144103. [DOI: 10.1063/1.4823729] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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33
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Lev B, Roux B, Noskov SY. Relative Free Energies for Hydration of Monovalent Ions from QM and QM/MM Simulations. J Chem Theory Comput 2013; 9:4165-75. [PMID: 26592407 DOI: 10.1021/ct400296w] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Methods directly evaluating the hydration structure and thermodynamics of physiologically relevant cations (Na(+), K(+), Cl(-), etc.) have wide ranging applications in the fields of inorganic, physical, and biological chemistry. All-atom simulations based on accurate potential energy surfaces appear to offer a viable option for assessing the chemistry of ion solvation. Although MD and free energy simulations of ion solvation with classical force fields have proven their usefulness, a number of challenges still remain. One of them is the difficulty of force field benchmarking and validation against structural and thermodynamic data obtained for a condensed phase. Hybrid quantum mechanical/molecular mechanical (QM/MM) models combined with sampling algorithms have the potential to provide an accurate solvation model and to incorporate the effects from the surrounding, which is often missing in gas-phase ab initio computations. Herein, we report the results from QM/MM free energy simulations of Na(+)/K(+) and Cl(-)/Br(-) hydration where we simultaneously characterized the relative thermodynamics of ion solvation and changes in the solvation structure. The Flexible Inner Region Ensemble Separator (FIRES) method was used to impose a spatial separation between QM region and the outer sphere of solvent molecules treated with the CHARMM27 force field. FEP calculations based on QM/MM simulations utilizing the CHARMM/deMon2k interface were performed with different basis set combinations for K(+)/Na(+) and Cl(-)/Br(-) perturbations to establish the dependence of the computed free energies on the basis set level. The dependence of the computed relative free energies on the size of the QM and MM regions is discussed. The current methodology offers an accurate description of structural and thermodynamic aspects of the hydration of alkali and halide ions in neat solvents and can be used to obtain thermodynamic data on ion solvation in condensed phase along with underlying structural properties of the ion-solvent system.
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Affiliation(s)
- Bogdan Lev
- Institute for Biocomplexity and Informatics, Department of Biological Sciences, The University of Calgary , 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Sciences, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States of America
| | - Sergei Yu Noskov
- Institute for Biocomplexity and Informatics, Department of Biological Sciences, The University of Calgary , 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
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34
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Boda D, Henderson D, Gillespie D. The role of solvation in the binding selectivity of the L-type calcium channel. J Chem Phys 2013; 139:055103. [DOI: 10.1063/1.4817205] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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35
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Saxena A, Sept D. Multisite Ion Models That Improve Coordination and Free Energy Calculations in Molecular Dynamics Simulations. J Chem Theory Comput 2013; 9:3538-42. [DOI: 10.1021/ct400177g] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Akansha Saxena
- Department
of Biomedical Engineering and Center for Computational Medicine and
Bioinformatics, University of Michigan,
Ann Arbor, Michigan 48109, United States
- Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180,
United States
| | - David Sept
- Department
of Biomedical Engineering and Center for Computational Medicine and
Bioinformatics, University of Michigan,
Ann Arbor, Michigan 48109, United States
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36
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Bankura A, Carnevale V, Klein ML. Hydration structure of salt solutions from ab initio molecular dynamics. J Chem Phys 2013; 138:014501. [PMID: 23298049 DOI: 10.1063/1.4772761] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The solvation structures of Na(+), K(+), and Cl(-) ions in aqueous solution have been investigated using density functional theory (DFT) based Car-Parrinello (CP) molecular dynamics (MD) simulations. CPMD trajectories were collected for systems containing three NaCl or KCl ion pairs solvated by 122 water molecules using three different but commonly employed density functionals (BLYP, HCTH, and PBE) with electron correlation treated at the level of the generalized gradient approximation (GGA). The effect of including dispersion forces was analyzed through the use of an empirical correction to the DFT-GGA scheme. Special attention was paid to the hydration characteristics, especially the structural properties of the first solvation shell of the ions, which was investigated through ion-water radial distribution functions, coordination numbers, and angular distribution functions. There are significant differences between the present results obtained from CPMD simulations and those provided by classical MD based on either the CHARMM force field or a polarizable model. Overall, the computed structural properties are in fair agreement with the available experimental results. In particular, the observed coordination numbers 5.0-5.5, 6.0-6.4, and 6.0-6.5 for Na(+), K(+), and Cl(-), respectively, are consistent with X-ray and neutron scattering studies but differ somewhat from some of the many other recent computational studies of these important systems. Possible reasons for the differences are discussed.
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Affiliation(s)
- Arindam Bankura
- Institute for Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
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Timko J, Kuyucak S. Investigation of polarization effects in the gramicidin A channel from ab initio molecular dynamics simulations. J Chem Phys 2013. [PMID: 23206041 DOI: 10.1063/1.4768247] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Polarization is an important component of molecular interactions and is expected to play a particularly significant role in inhomogeneous environments such as pores and interfaces. Here we investigate the effects of polarization in the gramicidin A ion channel by performing quantum mechanics/molecular mechanics molecular dynamics (MD) simulations and comparing the results with those obtained from classical MD simulations with non-polarizable force fields. We consider the dipole moments of backbone carbonyl groups and channel water molecules as well as a number of structural quantities of interest. The ab initio results show that the dipole moments of the carbonyl groups and water molecules are highly sensitive to the hydrogen bonds (H-bonds) they participate in. In the absence of a K(+) ion, water molecules in the channel are quite mobile, making the H-bond network highly dynamic. A central K(+) ion acts as an anchor for the channel waters, stabilizing the H-bond network and thereby increasing their average dipole moments. In contrast, the K(+) ion has little effect on the dipole moments of the neighboring carbonyl groups. The weakness of the ion-peptide interactions helps to explain the near diffusion-rate conductance of K(+) ions through the channel. We also address the sampling issue in relatively short ab initio MD simulations. Results obtained from a continuous 20 ps ab initio MD simulation are compared with those generated by sampling ten windows from a much longer classical MD simulation and running each window for 2 ps with ab initio MD. Both methods yield similar results for a number of quantities of interest, indicating that fluctuations are fast enough to justify the short ab initio MD simulations.
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Affiliation(s)
- Jeff Timko
- School of Physics, University of Sydney, Sydney, NSW 2006, Australia
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Bogatko S, Cauët E, Bylaska E, Schenter G, Fulton J, Weare J. The aqueous Ca2+ system, in comparison with Zn2+, Fe3+, and Al3+: an ab initio molecular dynamics study. Chemistry 2013; 19:3047-60. [PMID: 23315704 DOI: 10.1002/chem.201202821] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Indexed: 11/08/2022]
Abstract
Herein, we report on the structure and dynamics of the aqueous Ca(2+) system studied by using ab initio molecular dynamics (AIMD) simulations. Our detailed study revealed the formation of well-formed hydration shells with characteristics that were significantly different to those of bulk water. To facilitate a robust comparison with state-of-the-art X-ray absorption fine structure (XAFS) data, we employ a 1st principles MD-XAFS procedure and directly compare simulated and experimental XAFS spectra. A comparison of the data for the aqueous Ca(2+) system with those of the recently reported Zn(2+), Fe(3+), and Al(3+) species showed that many of their structural characteristics correlated well with charge density on the cation. Some very important exceptions were found, which indicated a strong sensitivity of the solvent structure towards the cation's valence electronic structure. Average dipole moments for the 2nd shell of all cations were suppressed relative to bulk water.
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Affiliation(s)
- Stuart Bogatko
- Chemistry and Biochemistry Department, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA.
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Criscenti LJ, Cygan RT. Molecular simulations of carbon dioxide and water: cation solvation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:87-94. [PMID: 22779448 DOI: 10.1021/es301608c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Proposed carbon dioxide sequestration scenarios in sedimentary reservoirs require investigation into the interactions between supercritical carbon dioxide, brines, and the mineral phases found in the basin and overlying caprock. Molecular simulations can help to understand the partitioning of metal cations between aqueous solutions and supercritical carbon dioxide where limited experimental data exist. In this effort, we used classical molecular dynamics simulations to compare the solvation of alkali and alkaline-earth metal cations in water and liquid CO(2) at 300 K by combining a flexible simple point charge model for water and an accurate flexible force field for CO(2). Solvation energies for these cations are larger in water than in carbon dioxide, suggesting that they will partition preferentially into water. In both aqueous and CO(2) solutions, the solvation energies decrease with cation size and increase with cation charge. However, changes in solvation energy with ionic radii are smaller in CO(2) than in water suggesting that the partitioning of cations into CO(2) will increase with ion size. Simulations of the interface between aqueous solution and supercritical CO(2) support this suggestion in that some large cations (e.g., Cs(+) and K(+)) partition into the CO(2) phase, often with a partial solvation sphere of water molecules.
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Affiliation(s)
- Louise J Criscenti
- Geochemistry Department, PO Box 5800 MS 0754, Sandia National Laboratories, Albuquerque, New Mexico 87185-0754, United States
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40
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Neyt JC, Wender A, Lachet V, Ghoufi A, Malfreyt P. Prediction of the concentration dependence of the surface tension and density of salt solutions: atomistic simulations using Drude oscillator polarizable and nonpolarizable models. Phys Chem Chem Phys 2013; 15:11679-90. [DOI: 10.1039/c3cp50904d] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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41
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Lev B, Noskov SY. Role of protein matrix rigidity and local polarization effects in the monovalent cation selectivity of crystallographic sites in the Na-coupled aspartate transporter GltPh. Phys Chem Chem Phys 2013; 15:2397-404. [DOI: 10.1039/c2cp42860a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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42
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Development and applications of the ABEEM fluctuating charge molecular force field in the ion-containing systems. Sci China Chem 2012. [DOI: 10.1007/s11426-012-4787-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Ren P, Chun J, Thomas DG, Schnieders MJ, Marucho M, Zhang J, Baker NA. Biomolecular electrostatics and solvation: a computational perspective. Q Rev Biophys 2012; 45:427-91. [PMID: 23217364 PMCID: PMC3533255 DOI: 10.1017/s003358351200011x] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
An understanding of molecular interactions is essential for insight into biological systems at the molecular scale. Among the various components of molecular interactions, electrostatics are of special importance because of their long-range nature and their influence on polar or charged molecules, including water, aqueous ions, proteins, nucleic acids, carbohydrates, and membrane lipids. In particular, robust models of electrostatic interactions are essential for understanding the solvation properties of biomolecules and the effects of solvation upon biomolecular folding, binding, enzyme catalysis, and dynamics. Electrostatics, therefore, are of central importance to understanding biomolecular structure and modeling interactions within and among biological molecules. This review discusses the solvation of biomolecules with a computational biophysics view toward describing the phenomenon. While our main focus lies on the computational aspect of the models, we provide an overview of the basic elements of biomolecular solvation (e.g. solvent structure, polarization, ion binding, and non-polar behavior) in order to provide a background to understand the different types of solvation models.
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Affiliation(s)
- Pengyu Ren
- Department of Biomedical Engineering, The University of Texas at Austin
| | | | | | | | - Marcelo Marucho
- Department of Physics and Astronomy, The University of Texas at San Antonio
| | - Jiajing Zhang
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Nathan A. Baker
- To whom correspondence should be addressed. Pacific Northwest National Laboratory, PO Box 999, MSID K7-29, Richland, WA 99352. Phone: +1-509-375-3997,
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Mao AH, Pappu RV. Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions. J Chem Phys 2012; 137:064104. [DOI: 10.1063/1.4742068] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Dahlgren B, Reif MM, Hünenberger PH, Hansen N. Calculation of Derivative Thermodynamic Hydration and Aqueous Partial Molar Properties of Ions Based on Atomistic Simulations. J Chem Theory Comput 2012; 8:3542-64. [DOI: 10.1021/ct300260q] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Björn Dahlgren
- Laboratory
of Physical Chemistry,
ETH Zürich, Zürich, Switzerland
| | - Maria M. Reif
- Institute for Molecular Modeling
and Simulation, University of Natural Resources and Life Sciences,
Vienna, Austria
| | | | - Niels Hansen
- Laboratory
of Physical Chemistry,
ETH Zürich, Zürich, Switzerland
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46
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Ouni O, Derbel N, Jaïdane N, Ruiz-López M. The K+ hydration shell structure in non-polar and low-polar environments. COMPUT THEOR CHEM 2012. [DOI: 10.1016/j.comptc.2011.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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47
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Rowley CN, Roux B. The Solvation Structure of Na(+) and K(+) in Liquid Water Determined from High Level ab Initio Molecular Dynamics Simulations. J Chem Theory Comput 2012; 8:3526-35. [PMID: 26593000 DOI: 10.1021/ct300091w] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Knowledge of the hydration structure of Na(+) and K(+) in the liquid phase has wide ranging implications in the field of biological chemistry. Despite numerous experimental and computational studies, even basic features such as the coordination number of these alkali ions in liquid water, thought to play a critical role in selectivity, continue to be the subject of intensive debates. Simulations based on accurate potential energy surfaces offer one approach to resolve these issues by providing reliable results on ion hydration. In this article, we report the results from molecular dynamics simulations of Na(+) and K(+) hydration based on a novel and rigorous strategy designed to overcome the challenges of QM/MM simulations of solvent molecules in the liquid phase. In this method, which we call Flexible Inner Region Ensemble Separator (FIRES), the ion and a fixed number of nearest water molecules form a dynamical and flexible inner region that is represented with high level ab initio quantum mechanical (QM) methods, while the water molecules from the surrounding bulk form an outer region that is represented by a polarizable molecular mechanical (MM) force field. Simulations yield rigorously correct thermodynamic averages as long as the solvent molecules in the flexible inner and outer regions are not allowed to exchange. Extensive FIRES simulations were carried out based on a QM/MM model in which the Na(+) or K(+) ion and the 12 nearest water molecules were represented by high level ab initio methods (RI-MP2/def2-TZVP and density functional theory with PBE/def2-TZVP), while the surrounding MM water molecules were represented by the polarizable SWM4-NDP potential. On the basis of these results, the ion coordination numbers are estimated to be within the range of 5.7-5.8 for Na(+) and 6.9-7.0 for K(+).
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Affiliation(s)
- Christopher N Rowley
- Department of Biochemistry and Molecular Biology, The University of Chicago , 929 East 57th Street, Chicago, Illinois, United States
| | - Benoıt Roux
- Department of Biochemistry and Molecular Biology, The University of Chicago , 929 East 57th Street, Chicago, Illinois, United States
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48
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Merchant S, Dixit PD, Dean KR, Asthagiri D. Ion-water clusters, bulk medium effects, and ion hydration. J Chem Phys 2011; 135:054505. [PMID: 21823710 DOI: 10.1063/1.3620077] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Thermochemistry of gas-phase ion-water clusters together with estimates of the hydration free energy of the clusters and the water ligands are used to calculate the hydration free energy of the ion. Often the hydration calculations use a continuum model of the solvent. The primitive quasichemical approximation to the quasichemical theory provides a transparent framework to anchor such efforts. Here we evaluate the approximations inherent in the primitive quasichemical approach and elucidate the different roles of the bulk medium. We find that the bulk medium can stabilize configurations of the cluster that are usually not observed in the gas phase, while also simultaneously lowering the excess chemical potential of the ion. This effect is more pronounced for soft ions. Since the coordination number that minimizes the excess chemical potential of the ion is identified as the optimal or most probable coordination number, for such soft ions the optimum cluster size and the hydration thermodynamics obtained with and without account of the bulk medium on the ion-water clustering reaction can be different. The ideas presented in this work are expected to be relevant to experimental studies that translate thermochemistry of ion-water clusters to the thermodynamics of the hydrated ion and to evolving theoretical approaches that combine high-level calculations on clusters with coarse-grained models of the medium.
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Affiliation(s)
- Safir Merchant
- Department of Chemical and Biomolecular Engineering, The Institute of NanoBioTechnology, Johns Hopkins University, Baltimore, Maryland 21218, USA
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Roux B, Bernèche S, Egwolf B, Lev B, Noskov SY, Rowley CN, Yu H. Ion selectivity in channels and transporters. ACTA ACUST UNITED AC 2011; 137:415-26. [PMID: 21518830 PMCID: PMC3082929 DOI: 10.1085/jgp.201010577] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Benoît Roux
- Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Sciences, University of Chicago, Chicago, IL 60637, USA. roux@uchicago.edu
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Abstract
Monovalent ion hydration entropies are analyzed via energetic partitioning of the potential distribution theorem free energy. Extensive molecular dynamics simulations and free energy calculations are performed over a range of temperatures to determine the electrostatic and van der Waals components of the entropy. The far-field electrostatic contribution is negative and small in magnitude, and it does not vary significantly as a function of ion size, consistent with dielectric models. The local electrostatic contribution, however, varies widely as a function of ion size; the sign yields a direct indication of the kosmotropic (strongly hydrated) or chaotropic (weakly hydrated) nature of the ion hydration. The results provide a thermodynamic signature for specific ion effects in hydration and are consistent with experiments that suggest minimal perturbations of water structure outside the first hydration shell. The hydration entropies are also examined in relation to the corresponding entropies for the isoelectronic rare gas pairs; an inverse correlation is observed, as expected from thermodynamic hydration data.
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Affiliation(s)
- Thomas L Beck
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, United States.
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