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Abstract
This review focuses on papers published since 2000 on the topic of the properties of solutes in water. More specifically, it evaluates the state of the art of our understanding of the complex relationship between the shape of a hydrophobe and the hydrophobic effect. To highlight this, we present a selection of references covering both empirical and molecular dynamics studies of small (molecular-scale) solutes. These include empirical studies of small molecules, synthetic hosts, crystalline monolayers, and proteins, as well as in silico investigations of entities such as idealized hard and soft spheres, small solutes, hydrophobic plates, artificial concavity, molecular hosts, carbon nanotubes and spheres, and proteins.
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Affiliation(s)
- Matthew B Hillyer
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118;
| | - Bruce C Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118;
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52
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Wang C, Ren P, Luo R. Ionic Solution: What Goes Right and Wrong with Continuum Solvation Modeling. J Phys Chem B 2017; 121:11169-11179. [PMID: 29164898 DOI: 10.1021/acs.jpcb.7b09616] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Solvent-mediated electrostatic interactions were well recognized to be important in the structure and function of molecular systems. Ionic interaction is an important component in electrostatic interactions, especially in highly charged molecules, such as nucleic acids. Here, we focus on the quality of the widely used Poisson-Boltzmann surface area (PBSA) continuum models in modeling ionic interactions by comparing with both explicit solvent simulations and the experiment. In this work, the molality-dependent chemical potentials for sodium chloride (NaCl) electrolyte were first simulated in the SPC/E explicit solvent. Our high-quality simulation agrees well with both the previous study and the experiment. Given the free-energy simulations in SPC/E as the benchmark, we used the same sets of snapshots collected in the SPC/E solvent model for PBSA free-energy calculations in the hope to achieve the maximum consistency between the two solvent models. Our comparative analysis shows that the molality-dependent chemical potentials of NaCl were reproduced well with both linear PB and nonlinear PB methods, although nonlinear PB agrees better with SPC/E and the experiment. Our free-energy simulations also show that the presence of salt increases the hydrophobic effect in a nonlinear fashion, in qualitative agreement with previous theoretical studies of Onsager and Samaras. However, the lack of molality-dependency in the nonelectrostatics continuum models dramatically reduces the overall quality of PBSA methods in modeling salt-dependent energetics. These analyses point to further improvements needed for more robust modeling of solvent-mediated interactions by the continuum solvation frameworks.
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Affiliation(s)
| | - Pengyu Ren
- Department of Biomedical Engineering, University of Texas , Austin, Texas 78712, United States
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53
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Lake PT, McCullagh M. Implicit Solvation Using the Superposition Approximation (IS-SPA): An Implicit Treatment of the Nonpolar Component to Solvation for Simulating Molecular Aggregation. J Chem Theory Comput 2017; 13:5911-5924. [PMID: 29120632 DOI: 10.1021/acs.jctc.7b00698] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nonpolar solute-solvent interactions are the driving force for aggregation in important chemical and biological phenomena including protein folding, peptide self-assembly, and oil-water emulsion formation. Currently, the most accurate and computationally efficient description of these processes requires an explicit treatment of all solvent and solute atoms. Previous computationally feasible implicit solvent models, such as solute surface area approaches, are unsuccessful at capturing aggregation features including both structural and energetic trends while more theoretically rigorous approaches, such as Reference Interaction Site Model (RISM), are accurate but extremely computationally demanding. Our approach, denoted Implicit Solvation using the Superposition Approximation (IS-SPA), builds on previous theory utilizing the Kirkwood superposition approximation to approximate the mean force of the solvent from solute parameters. We introduce and verify a parabolic first solvation shell truncation of atomic solvation, fitting water distributions around a molecule, and a Monte Carlo integration of the mean solvent force. These extensions allow this method to be implemented as an efficient nonpolar implicit solvent model for molecular simulation. The approximations in IS-SPA are first explored and justified for the homodimerization of an array of different sized Lennard-Jones spheres. The accuracy and transferability of the approach are demonstrated by its ability to capture the position and relative energies of the desolvation barrier and free energy minimum of alkane homodimers. The model is then shown to reproduce the phase separation and solubility of cyclohexane and water. These promising results, coupled with 2 orders of magnitude speed-up for dilute systems as compared to explicit solvent simulations, demonstrate that IS-SPA is an appealing approach to boost the time- and length-scale of molecular aggregation simulations.
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Affiliation(s)
- Peter T Lake
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States
| | - Martin McCullagh
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States
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54
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Deng N, Wickstrom L, Cieplak P, Lin C, Yang D. Resolving the Ligand-Binding Specificity in c-MYC G-Quadruplex DNA: Absolute Binding Free Energy Calculations and SPR Experiment. J Phys Chem B 2017; 121:10484-10497. [PMID: 29086571 DOI: 10.1021/acs.jpcb.7b09406] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We report the absolute binding free energy calculation and surface plasmon resonance (SPR) experiment for ligand binding with the c-MYC G-quadruplex DNA. The unimolecular parallel DNA G-quadruplex formed in nuclease hypersensitivity element III1 of the c-MYC gene promoter regulates the c-MYC transcription and is recognized as an emerging drug target for cancer therapy. Quindoline derivatives have been shown to stabilize the G-quadruplex and inhibit the c-MYC expression in cancer cells. NMR revealed two binding sites located at the 5' and 3' termini of the G-quadruplex. Questions about which site is more favored and the basis for the ligand-induced binding site formation remain unresolved. Here, we employ two absolute binding free energy methods, the double decoupling and the potential of mean force methods, to dissect the ligand-binding specificity in the c-MYC G-quadruplex. The calculated absolute binding free energies are in general agreement with the SPR result and suggest that quindoline has a slight preference for the 5' site. The flanking residues around the two sites undergo significant reorganization as the ligand unbinds, which provides evidence for ligand-induced binding pocket formation. The results help interpret experimental data and inform rational design of small molecules targeting the c-MYC G-quadruplex.
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Affiliation(s)
- Nanjie Deng
- Department of Chemistry and Physical Sciences, Pace University , 1 Pace Plaza, New York, New York 10038, United States
| | - Lauren Wickstrom
- Department of Science, Borough of Manhattan Community College, the City University of New York , New York, New York 10007, United States
| | - Piotr Cieplak
- Sanford Burnham Prebys Medical Discovery Institute , La Jolla, San Diego, California 92037, United States
| | - Clement Lin
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University , West Lafayette, Indiana 47907, United States
| | - Danzhou Yang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University , West Lafayette, Indiana 47907, United States
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55
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van der Vegt NFA, Nayar D. The Hydrophobic Effect and the Role of Cosolvents. J Phys Chem B 2017; 121:9986-9998. [DOI: 10.1021/acs.jpcb.7b06453] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Nico F. A. van der Vegt
- Eduard-Zintl-Institut für
Anorganische und Physikalische Chemie, Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany
| | - Divya Nayar
- Eduard-Zintl-Institut für
Anorganische und Physikalische Chemie, Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany
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56
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Ardham VR, Leroy F. Thermodynamics of atomistic and coarse-grained models of water on nonpolar surfaces. J Chem Phys 2017; 147:074702. [DOI: 10.1063/1.4999337] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Vikram Reddy Ardham
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
| | - Frédéric Leroy
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse 8, 64287 Darmstadt, Germany
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57
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Drake JA, Harris RC, Pettitt BM. Solvation Thermodynamics of Oligoglycine with Respect to Chain Length and Flexibility. Biophys J 2017; 111:756-767. [PMID: 27558719 DOI: 10.1016/j.bpj.2016.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/30/2016] [Accepted: 07/06/2016] [Indexed: 01/24/2023] Open
Abstract
Oligoglycine is a backbone mimic for all proteins and is prevalent in the sequences of intrinsically disordered proteins. We have computed the absolute chemical potential of glycine oligomers at infinite dilution by simulation with the CHARMM36 and Amber ff12SB force fields. We performed a thermodynamic decomposition of the solvation free energy (ΔG(sol)) of Gly2-5 into enthalpic (ΔH(sol)) and entropic (ΔS(sol)) components as well as their van der Waals and electrostatic contributions. Gly2-5 was either constrained to a rigid/extended conformation or allowed to be completely flexible during simulations to assess the effects of flexibility on these thermodynamic quantities. For both rigid and flexible oligoglycine models, the decrease in ΔG(sol) with chain length is enthalpically driven with only weak entropic compensation. However, the apparent rates of decrease of ΔG(sol), ΔH(sol), ΔS(sol), and their elec and vdw components differ for the rigid and flexible models. Thus, we find solvation entropy does not drive aggregation for this system and may not explain the collapse of long oligoglycines. Additionally, both force fields yield very similar thermodynamic scaling relationships with respect to chain length despite both force fields generating different conformational ensembles of various oligoglycine chains.
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Affiliation(s)
- Justin A Drake
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas
| | - Robert C Harris
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania
| | - B Montgomery Pettitt
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas.
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58
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Hajari T, Bandyopadhyay S. Water structure around hydrophobic amino acid side chain analogs using different water models. J Chem Phys 2017; 146:225104. [PMID: 29166083 DOI: 10.1063/1.4985671] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The water structure around hydrophobic groups governs various biochemical processes. There is an ongoing debate on whether water molecules near hydrophobic groups are more ordered with greater participation in water-water hydrogen bonding with respect to water in the pure bulk state. The water structure around six different hydrophobic amino acid side chain analog molecules has been studied in pure water using molecular dynamics simulations. The analysis of water tetrahedral order parameter and the number of hydrogen bonds formed by the individual water molecules in the first hydration shell of the hydrophobic analogs provide evidence that both ordering and hydrogen bonds involving water molecules are to some extent reduced in the hydrophobic hydration shell. It is revealed that the water tetrahedrality in the outer part of the first hydrophobic hydration shell is equivalent to bulk water for all the water models except for the TIP4P-2005 model which shows marginally higher tetrahedrality. However, irrespective of the model employed, water tetrahedrality has always been found to be reduced in the inner part of the first hydration shell, which eventually makes the overall water tetrahedrality in the first hydrophobic hydration shell marginally lower than that observed for pure bulk water. Importantly, it is noticed that the decrease in water structuring exhibits solute size dependencies. Around a small solute like methane, the water tetrahedral ordering or hydrogen bonding propensity is quite similar to that of the bulk state. The effect, reduction in water structuring, is however more pronounced for relatively larger solutes.
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Affiliation(s)
- Timir Hajari
- Molecular Modeling Laboratory, Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India
| | - Sanjoy Bandyopadhyay
- Molecular Modeling Laboratory, Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India
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59
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Zhang J, Zhang H, Wu T, Wang Q, van der Spoel D. Comparison of Implicit and Explicit Solvent Models for the Calculation of Solvation Free Energy in Organic Solvents. J Chem Theory Comput 2017; 13:1034-1043. [DOI: 10.1021/acs.jctc.7b00169] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jin Zhang
- Department
of Chemistry and Soft Matter Research Center, Zhejiang University, Hangzhou 310027, China
| | - Haiyang Zhang
- Department
of Biological Science and Engineering, School of Chemistry and Biological
Engineering, University of Science and Technology Beijing, 100083 Beijing, China
| | - Tao Wu
- Department
of Chemistry and Soft Matter Research Center, Zhejiang University, Hangzhou 310027, China
| | - Qi Wang
- Department
of Chemistry and Soft Matter Research Center, Zhejiang University, Hangzhou 310027, China
| | - David van der Spoel
- Uppsala
Center for Computational Chemistry, Science for Life Laboratory, Department
of Cell and Molecular Biology, Uppsala University, Husargatan 3, Box
596, SE-75124 Uppsala, Sweden
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60
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Ou SC, Drake JA, Pettitt BM. Nonpolar Solvation Free Energy from Proximal Distribution Functions. J Phys Chem B 2017; 121:3555-3564. [PMID: 27992228 DOI: 10.1021/acs.jpcb.6b09528] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Using precomputed near neighbor or proximal distribution functions (pDFs) that approximate solvent density about atoms in a chemically bonded context one can estimate the solvation structures around complex solutes and the corresponding solute-solvent energetics. In this contribution, we extend this technique to calculate the solvation free energies (ΔG) of a variety of solutes. In particular we use pDFs computed for small peptide molecules to estimate ΔG for larger peptide systems. We separately compute the non polar (ΔGvdW) and electrostatic (ΔGelec) components of the underlying potential model. Here we show how the former can be estimated by thermodynamic integration using pDF-reconstructed solute-solvent interaction energy. The electrostatic component can be approximated with Linear Response theory as half of the electrostatic solute-solvent interaction energy. We test the method by calculating the solvation free energies of butane, propanol, polyalanine, and polyglycine and by comparing with traditional free energy simulations. Results indicate that the pDF-reconstruction algorithm approximately reproduces ΔGvdW calculated by benchmark free energy simulations to within ∼ kcal/mol accuracy. The use of transferable pDFs for each solute atom allows for a rapid estimation of ΔG for arbitrary molecular systems.
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Affiliation(s)
- Shu-Ching Ou
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
| | - Justin A Drake
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
| | - B Montgomery Pettitt
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
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61
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Chen Z. Minimization and Eulerian Formulation of Differential Geormetry Based Nonpolar Multiscale Solvation Models. COMPUTATIONAL AND MATHEMATICAL BIOPHYSICS 2016. [DOI: 10.1515/mlbmb-2016-0005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
AbstractIn this work, the existence of a global minimizer for the previous Lagrangian formulation of nonpolar
solvation model proposed in [1] has been proved. One of the proofs involves a construction of a phase field
model that converges to the Lagrangian formulation. Moreover, an Eulerian formulation of nonpolar solvation
model is proposed and implemented under a similar parameterization scheme to that in [1]. By doing so,
the connection, similarity and difference between the Eulerian formulation and its Lagrangian counterpart
can be analyzed. It turns out that both of them have a great potential in solvation prediction for nonpolar
molecules, while their decompositions of attractive and repulsive parts are different. That indicates a distinction
between phase field models of solvation and our Eulerian formulation.
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Affiliation(s)
- Zhan Chen
- 1Department of Mathematical Sciences, Georgia Southern University, Statesboro, GA, 30460,USA
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62
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Enami S, Fujii T, Sakamoto Y, Hama T, Kajii Y. Carboxylate Ion Availability at the Air–Water Interface. J Phys Chem A 2016; 120:9224-9234. [DOI: 10.1021/acs.jpca.6b08868] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shinichi Enami
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Tomihide Fujii
- Graduate School of Global Environmental
Studies, Kyoto University, Kyoto 606-8501, Japan
| | - Yosuke Sakamoto
- Graduate School of Global Environmental
Studies, Kyoto University, Kyoto 606-8501, Japan
- Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8316, Japan
| | - Tetsuya Hama
- Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
| | - Yoshizumi Kajii
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
- Graduate School of Global Environmental
Studies, Kyoto University, Kyoto 606-8501, Japan
- Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8316, Japan
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63
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Wang C, Nguyen PH, Pham K, Huynh D, Le TBN, Wang H, Ren P, Luo R. Calculating protein-ligand binding affinities with MMPBSA: Method and error analysis. J Comput Chem 2016; 37:2436-46. [PMID: 27510546 PMCID: PMC5018451 DOI: 10.1002/jcc.24467] [Citation(s) in RCA: 156] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 07/13/2016] [Indexed: 11/07/2022]
Abstract
Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) methods have become widely adopted in estimating protein-ligand binding affinities due to their efficiency and high correlation with experiment. Here different computational alternatives were investigated to assess their impact to the agreement of MMPBSA calculations with experiment. Seven receptor families with both high-quality crystal structures and binding affinities were selected. First the performance of nonpolar solvation models was studied and it was found that the modern approach that separately models hydrophobic and dispersion interactions dramatically reduces RMSD's of computed relative binding affinities. The numerical setup of the Poisson-Boltzmann methods was analyzed next. The data shows that the impact of grid spacing to the quality of MMPBSA calculations is small: the numerical error at the grid spacing of 0.5 Å is already small enough to be negligible. The impact of different atomic radius sets and different molecular surface definitions was further analyzed and weak influences were found on the agreement with experiment. The influence of solute dielectric constant was also analyzed: a higher dielectric constant generally improves the overall agreement with experiment, especially for highly charged binding pockets. The data also showed that the converged simulations caused slight reduction in the agreement with experiment. Finally the direction of estimating absolute binding free energies was briefly explored. Upon correction of the binding-induced rearrangement free energy and the binding entropy lost, the errors in absolute binding affinities were also reduced dramatically when the modern nonpolar solvent model was used, although further developments were apparently necessary to further improve the MMPBSA methods. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Changhao Wang
- Chemical and Materials Physics Graduate Program, Irvine, California, 92697
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
- Department of Physics and Astronomy, University of California, Irvine, California, 92697
| | - Peter H Nguyen
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | - Kevin Pham
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | - Danielle Huynh
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | | | - Hongli Wang
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697
| | - Pengyu Ren
- Department of Biomedical Engineering, University of Texas, Austin, Texas, 78712
| | - Ray Luo
- Chemical and Materials Physics Graduate Program, Irvine, California, 92697.
- Department of Molecular Biology and Biochemistry, Irvine, California, 92697.
- Department of Chemical Engineering and Materials Science, Irvine, California, 92697.
- Department of Biomedical Engineering, University of California, Irvine, California, 92697.
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64
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Nguyen DD, Wei GW. The impact of surface area, volume, curvature, and Lennard-Jones potential to solvation modeling. J Comput Chem 2016; 38:24-36. [PMID: 27718270 DOI: 10.1002/jcc.24512] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 08/17/2016] [Accepted: 08/30/2016] [Indexed: 12/24/2022]
Abstract
This article explores the impact of surface area, volume, curvature, and Lennard-Jones (LJ) potential on solvation free energy predictions. Rigidity surfaces are utilized to generate robust analytical expressions for maximum, minimum, mean, and Gaussian curvatures of solvent-solute interfaces, and define a generalized Poisson-Boltzmann (GPB) equation with a smooth dielectric profile. Extensive correlation analysis is performed to examine the linear dependence of surface area, surface enclosed volume, maximum curvature, minimum curvature, mean curvature, and Gaussian curvature for solvation modeling. It is found that surface area and surfaces enclosed volumes are highly correlated to each other's, and poorly correlated to various curvatures for six test sets of molecules. Different curvatures are weakly correlated to each other for six test sets of molecules, but are strongly correlated to each other within each test set of molecules. Based on correlation analysis, we construct twenty six nontrivial nonpolar solvation models. Our numerical results reveal that the LJ potential plays a vital role in nonpolar solvation modeling, especially for molecules involving strong van der Waals interactions. It is found that curvatures are at least as important as surface area or surface enclosed volume in nonpolar solvation modeling. In conjugation with the GPB model, various curvature-based nonpolar solvation models are shown to offer some of the best solvation free energy predictions for a wide range of test sets. For example, root mean square errors from a model constituting surface area, volume, mean curvature, and LJ potential are less than 0.42 kcal/mol for all test sets. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Duc D Nguyen
- Department of Mathematics, Michigan State University, Michigan, 48824
| | - Guo-Wei Wei
- Department of Mathematics, Michigan State University, Michigan, 48824.,Department of Electrical and Computer Engineering, Michigan State University, Michigan, 48824.,Department of Biochemistry and Molecular Biology, Michigan State University, Michigan, 48824
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65
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Lim HK, Lee H, Kim H. A Seamless Grid-Based Interface for Mean-Field QM/MM Coupled with Efficient Solvation Free Energy Calculations. J Chem Theory Comput 2016; 12:5088-5099. [DOI: 10.1021/acs.jctc.6b00469] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hyung-Kyu Lim
- Graduate School of Energy,
Environment, Water, and Sustainability (EEWS), Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 305-701, Korea
| | - Hankyul Lee
- Graduate School of Energy,
Environment, Water, and Sustainability (EEWS), Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 305-701, Korea
| | - Hyungjun Kim
- Graduate School of Energy,
Environment, Water, and Sustainability (EEWS), Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 305-701, Korea
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66
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Schauperl M, Podewitz M, Waldner BJ, Liedl KR. Enthalpic and Entropic Contributions to Hydrophobicity. J Chem Theory Comput 2016; 12:4600-10. [PMID: 27442443 PMCID: PMC5024328 DOI: 10.1021/acs.jctc.6b00422] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hydrophobic hydration plays a key role in a vast variety of biological processes, ranging from the formation of cells to protein folding and ligand binding. Hydrophobicity scales simplify the complex process of hydration by assigning a value describing the averaged hydrophobic character to each amino acid. Previously published scales were not able to calculate the enthalpic and entropic contributions to the hydrophobicity directly. We present a new method, based on Molecular Dynamics simulations and Grid Inhomogeneous Solvation Theory, that calculates hydrophobicity from enthalpic and entropic contributions. Instead of deriving these quantities from the temperature dependence of the free energy of hydration or as residual of the free energy and the enthalpy, we directly obtain these values from the phase space occupied by water molecules. Additionally, our method is able to identify regions with specific enthalpic and entropic properties, allowing to identify so-called "unhappy water" molecules, which are characterized by weak enthalpic interactions and unfavorable entropic constraints.
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Affiliation(s)
- Michael Schauperl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck , Innrain 80-82, A-6020 Innsbruck, Tyrol, Austria
| | - Maren Podewitz
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck , Innrain 80-82, A-6020 Innsbruck, Tyrol, Austria
| | - Birgit J Waldner
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck , Innrain 80-82, A-6020 Innsbruck, Tyrol, Austria
| | - Klaus R Liedl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck , Innrain 80-82, A-6020 Innsbruck, Tyrol, Austria
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67
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Haider K, Wickstrom L, Ramsey S, Gilson MK, Kurtzman T. Enthalpic Breakdown of Water Structure on Protein Active-Site Surfaces. J Phys Chem B 2016; 120:8743-56. [PMID: 27169482 DOI: 10.1021/acs.jpcb.6b01094] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The principles underlying water reorganization around simple nonpolar solutes are well understood and provide the framework for the classical hydrophobic effect, whereby water molecules structure themselves around solutes so that they maintain favorable energetic contacts with both the solute and the other water molecules. However, for certain solute surface topographies, water molecules, due to their geometry and size, are unable to simultaneously maintain favorable energetic contacts with both the surface and neighboring water molecules. In this study, we analyze the solvation of ligand-binding sites for six structurally diverse proteins using hydration site analysis and measures of local water structure, in order to identify surfaces at which water molecules are unable to structure themselves in a way that maintains favorable enthalpy relative to bulk water. These surfaces are characterized by a high degree of enclosure, weak solute-water interactions, and surface constraints that induce unfavorable pair interactions between neighboring water molecules. Additionally, we find that the solvation of charged side chains in an active site generally results in favorable enthalpy but can also lead to pair interactions between neighboring water molecules that are significantly unfavorable relative to bulk water. We find that frustrated local structure can occur not only in apolar and weakly polar pockets, where overall enthalpy tends to be unfavorable, but also in charged pockets, where overall water enthalpy tends to be favorable. The characterization of local water structure in these terms may prove useful for evaluating the displacement of water from diverse protein active-site environments.
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Affiliation(s)
- Kamran Haider
- Department of Chemistry, Lehman College, The City University of New York , 250 Bedford Park Boulevard West, Bronx, New York 10468, United States
| | - Lauren Wickstrom
- Borough of Manhattan Community College, Department of Science, The City University of New York , 199 Chambers Street, New York, New York 10007, United States
| | - Steven Ramsey
- Department of Chemistry, Lehman College, The City University of New York , 250 Bedford Park Boulevard West, Bronx, New York 10468, United States.,Ph.D. Program in Biochemistry, The Graduate Center of The City University of New York , 365 Fifth Avenue, New York, New York 10016, United States
| | - Michael K Gilson
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego , 9500 Gilman Drive, La Jolla, California 92093-0736, United States
| | - Tom Kurtzman
- Department of Chemistry, Lehman College, The City University of New York , 250 Bedford Park Boulevard West, Bronx, New York 10468, United States.,Ph.D. Program in Biochemistry, The Graduate Center of The City University of New York , 365 Fifth Avenue, New York, New York 10016, United States.,Ph.D. Program in Chemistry, The Graduate Center of The City University of New York , 365 Fifth Avenue, New York, New York 10016, United States
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68
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Lapelosa M, Patapoff TW, Zarraga IE. Molecular simulations of micellar aggregation of polysorbate 20 ester fractions and their interaction with N-phenyl-1-naphthylamine dye. Biophys Chem 2016; 213:17-24. [DOI: 10.1016/j.bpc.2016.03.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 03/22/2016] [Accepted: 03/22/2016] [Indexed: 11/30/2022]
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69
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Affiliation(s)
- Dor Ben-Amotz
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907;
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70
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Cabaleiro-Lago EM, Rodríguez-Otero J, Gil A. Comment on "Theoretical studies on a carbonaceous molecular bearing: association thermodynamics and dual-mode rolling dynamics" by H. Isobe, K. Nakamura, S. Hitosugi, S. Sato, H. Tokoyama, H. Yamakado, K. Ohno and H. Kono, Chem. Sci., 2015, 6, 2746. Chem Sci 2016; 7:2924-2928. [PMID: 30090286 PMCID: PMC6054031 DOI: 10.1039/c5sc04676a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/05/2016] [Indexed: 12/03/2022] Open
Abstract
The LC-BLYP functional accompanied with proper calculations leads to unreliable results for systems governed by π···π interactions. It seems quite clear that a good representation of dispersion interactions is required, so DFT must be supplemented (through the DFT-D formalism or the many-body dispersion method) in order to afford good results.
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Affiliation(s)
- Enrique M Cabaleiro-Lago
- Departamento de Química Física , Facultad de Ciencias , Universidade de Santiago de Compostela , Campus de Lugo , Av. Alfonso X El Sabio, s/n , 27002 Lugo , Galicia , Spain .
| | - Jesús Rodríguez-Otero
- CIQUS and Facultade de Química (Departamento de Química Física) , Universidade de Santiago de Compostela , 15782 Santiago de Compostela , Galicia , Spain .
| | - Adrià Gil
- Centro de Química e Bioquímica , DQB , Faculdade de Ciências , Universidade de Lisboa , Campo Grande , 1749-016 Lisboa , Portugal
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71
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Rane K, van der Vegt NFA. Understanding the influence of capillary waves on solvation at the liquid-vapor interface. J Chem Phys 2016; 144:114111. [DOI: 10.1063/1.4943781] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Kaustubh Rane
- Eduard-Zintl-Institut für Anorganische and Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Strasse 10, 64287 Darmstadt, Germany
| | - Nico F. A. van der Vegt
- Eduard-Zintl-Institut für Anorganische and Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Strasse 10, 64287 Darmstadt, Germany
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72
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Hajari T, van der Vegt NFA. Solvation thermodynamics of amino acid side chains on a short peptide backbone. J Chem Phys 2016; 142:144502. [PMID: 25877585 DOI: 10.1063/1.4917076] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydration process of side chain analogue molecules differs from that of the actual amino acid side chains in peptides and proteins owing to the effects of the peptide backbone on the aqueous solvent environment. A recent molecular simulation study has provided evidence that all nonpolar side chains, attached to a short peptide backbone, are considerably less hydrophobic than the free side chain analogue molecules. In contrast to this, the hydrophilicity of the polar side chains is hardly affected by the backbone. To analyze the origin of these observations, we here present a molecular simulation study on temperature dependent solvation free energies of nonpolar and polar side chains attached to a short peptide backbone. The estimated solvation entropies and enthalpies of the various amino acid side chains are compared with existing side chain analogue data. The solvation entropies and enthalpies of the polar side chains are negative, but in absolute magnitude smaller compared with the corresponding analogue data. The observed differences are large; however, owing to a nearly perfect enthalpy-entropy compensation, the solvation free energies of polar side chains remain largely unaffected by the peptide backbone. We find that a similar compensation does not apply to the nonpolar side chains; while the backbone greatly reduces the unfavorable solvation entropies, the solvation enthalpies are either more favorable or only marginally affected. This results in a very small unfavorable free energy cost, or even free energy gain, of solvating the nonpolar side chains in strong contrast to solvation of small hydrophobic or nonpolar molecules in bulk water. The solvation free energies of nonpolar side chains have been furthermore decomposed into a repulsive cavity formation contribution and an attractive dispersion free energy contribution. We find that cavity formation next to the peptide backbone is entropically favored over formation of similar sized nonpolar side chain cavities in bulk water, in agreement with earlier work in the literature on analysis of cavity fluctuations at nonpolar molecular surfaces. The cavity and dispersion interaction contributions correlate quite well with the solvent accessible surface area of the nonpolar side chains attached to the backbone. This correlation however is weak for the overall solvation free energies owing to the fact that the cavity and dispersion free energy contributions are almost exactly cancelling each other.
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Affiliation(s)
- Timir Hajari
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany
| | - Nico F A van der Vegt
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany
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73
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Mochizuki K, Koga K. Cononsolvency behavior of hydrophobes in water + methanol mixtures. Phys Chem Chem Phys 2016; 18:16188-95. [DOI: 10.1039/c6cp01496h] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The molecular origin of cononsolvency behavior is explored using molecular dynamics simulations.
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Affiliation(s)
- Kenji Mochizuki
- Department of Chemistry
- Faculty of Science
- Okayama University
- Okayama 700-8530
- Japan
| | - Kenichiro Koga
- Department of Chemistry
- Faculty of Science
- Okayama University
- Okayama 700-8530
- Japan
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74
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Ou SC, Cui D, Patel S. Molecular modeling of ions at interfaces: exploring similarities to hydrophobic solvation through the lens of induced aqueous interfacial fluctuations. Phys Chem Chem Phys 2016; 18:30357-30365. [DOI: 10.1039/c6cp04112d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ion specific effects are ubiquitous in chemistry and biology.
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Affiliation(s)
- Shu-Ching Ou
- Sealy Center for Structural Biology and Molecular Biophysics
- University of Texas Medical Branch
- 301 University Boulevard
- Galveston
- USA
| | - Di Cui
- Department of Chemistry
- Temple University
- Philadelphia
- USA
| | - Sandeep Patel
- Department of Chemistry and Biochemistry
- University of Delaware
- Newark
- USA
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75
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Schravendijk P, van der Vegt NFA. From Hydrophobic to Hydrophilic Solvation: An Application to Hydration of Benzene. J Chem Theory Comput 2015; 1:643-52. [PMID: 26641686 DOI: 10.1021/ct049841c] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report a computer simulation study on the hydration of benzene, which, despite being hydrophobic, is a weak hydrogen bond acceptor. The effect of benzene-water hydrogen bonding on the hydration free energy has been analyzed in terms of solute-solvent energies and entropies. Our calculations show that benzene-water hydrogen bonding restricts the number of arrangements possible for the water molecules resulting in a more unfavorable (negative) solute-solvent entropy change than observed for a 'nonpolar benzene' not capable of accepting water hydrogen bonds. More favorable hydration free energies of aromatic hydrocarbons in comparison with aliphatic hydrocarbons observed experimentally as well as in our calculations must therefore be a result of more favorable solute-solvent interaction energies. This result supports the view that lower aqueous solubilities of nonpolar molecules compared to polar molecules are due to a lack of favorable electrostatic interactions with water molecules. The calculated hydration free energy, enthalpy, entropy, and hydration heat capacity of benzene are in good agreement with experimentally reported values.
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Affiliation(s)
- Pim Schravendijk
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
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76
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Swanson JMJ, Adcock SA, McCammon JA. Optimized Radii for Poisson-Boltzmann Calculations with the AMBER Force Field. J Chem Theory Comput 2015; 1:484-93. [PMID: 26641515 DOI: 10.1021/ct049834o] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Implicit solvent models are a standard tool for assessing the electrostatics of biomolecular systems. The accuracy of quantitative predictions, such as pKa values, transfer free energies, binding energies, and solvation forces, is strongly dependent on one's choice of continuum parameters: the solute charges, dielectric coefficient, and radii, which define the dielectric boundary. To ensure quantitative accuracy, these parameters can be benchmarked against explicit solvent simulations. Here we present two sets of optimized radii to define either abrupt or cubic-spline smoothed dielectric boundaries in Poisson-Boltzmann calculations of protein systems with AMBER (parm99) charges. Spline smoothing stabilizes the electrostatic potential at the molecular surface, allowing for continuum force calculations. Most implementations, however, require significantly different radii than the abrupt boundary surfaces. The optimal continuum radii are initially approximated from the solvent radial charge distribution surrounding each atom type. A genetic algorithm is then used to fine-tune the starting values to reproduce charging free energies measured from explicit solvent simulations. The optimized radii are tested on four protein-like polypeptides. The results show increased accuracy of molecular solvation energies and atomic forces relative to commonly used continuum parameter sets. These radii are suitable for Poisson-Boltzmann calculations with the AMBER force field and offer energetic congruence to any model that combines molecular mechanics and Poisson-Boltzmann solvation energies.
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Affiliation(s)
- Jessica M J Swanson
- Howard Hughes Medical Institute, Center for Theoretical Biological Physics, Department of Chemistry and Biochemistry, and Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0365
| | - Stewart A Adcock
- Howard Hughes Medical Institute, Center for Theoretical Biological Physics, Department of Chemistry and Biochemistry, and Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0365
| | - J Andrew McCammon
- Howard Hughes Medical Institute, Center for Theoretical Biological Physics, Department of Chemistry and Biochemistry, and Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0365
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77
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Almlöf M, Carlsson J, Åqvist J. Improving the Accuracy of the Linear Interaction Energy Method for Solvation Free Energies. J Chem Theory Comput 2015; 3:2162-75. [PMID: 26636209 DOI: 10.1021/ct700106b] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A linear response method for estimating the free energy of solvation is presented and validated using explicit solvent molecular dynamics, thermodynamic perturbation calculations, and experimental data. The electrostatic contribution to the solvation free energy is calculated using a linear response estimate, which is obtained by comparison to the free energy calculated using thermodynamic perturbation. Systematic deviations from the value of (1)/2 in the potential energy scaling factor are observed for some types of compounds, and these are taken into account by introducing specific coefficients for different chemical groups. The derived model reduces the rms error of the linear response estimate significantly from 1.6 to 0.3 kcal/mol on a training set of 221 molecules used to parametrize the model and from 3.7 to 1.3 kcal/mol on a test set of 355 molecules that were not used in the derivation of the model. The total solvation free energy is estimated by combining the derived model with an empirical size dependent term for predicting the nonpolar contribution. Using this model, the experimental hydration free energies for 192 molecules are reproduced with an rms error of 1.1 kcal/mol. The use of LIE in simplified binding free energy calculations to predict protein-ligand binding free energies is also discussed.
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Affiliation(s)
- Martin Almlöf
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, SE-751 24 Uppsala, Sweden
| | - Jens Carlsson
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, SE-751 24 Uppsala, Sweden
| | - Johan Åqvist
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, SE-751 24 Uppsala, Sweden
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78
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Swanson JMJ, Wagoner JA, Baker NA, McCammon JA. Optimizing the Poisson Dielectric Boundary with Explicit Solvent Forces and Energies: Lessons Learned with Atom-Centered Dielectric Functions. J Chem Theory Comput 2015; 3:170-83. [PMID: 26627162 DOI: 10.1021/ct600216k] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Accurate implicit solvent models require parameters that have been optimized in a system- or atom-specific manner on the basis of experimental data or more rigorous explicit solvent simulations. Models based on the Poisson or Poisson-Boltzmann equation are particularly sensitive to the nature and location of the boundary which separates the low dielectric solute from the high dielectric solvent. Here, we present a novel method for optimizing the solute radii, which define the dielectric boundary, on the basis of forces and energies from explicit solvent simulations. We use this method to optimize radii for protein systems defined by AMBER ff99 partial charges and a spline-smoothed solute surface. The spline-smoothed surface is an atom-centered dielectric function that enables stable and efficient force calculations. We explore the relative performance of radii optimized with forces alone and those optimized with forces and energies. We show that our radii reproduce the explicit solvent forces and energies more accurately than four other parameter sets commonly used in conjunction with the AMBER force field, each of which has been appropriately scaled for spline-smoothed surfaces. Finally, we demonstrate that spline-smoothed surfaces show surprising accuracy for small, compact systems but may have limitations for highly solvated protein systems. The optimization method presented here is efficient and applicable to any system with explicit solvent parameters. It can be used to determine the optimal continuum parameters when experimental solvation energies are unavailable and the computational costs of explicit solvent charging free energies are prohibitive.
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Affiliation(s)
- Jessica M J Swanson
- Howard Hughes Medical Institute, Center for Theoretical Biological Physics, Department of Chemistry and Biochemistry and Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0365
| | - Jason A Wagoner
- Howard Hughes Medical Institute, Center for Theoretical Biological Physics, Department of Chemistry and Biochemistry and Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0365
| | - Nathan A Baker
- Howard Hughes Medical Institute, Center for Theoretical Biological Physics, Department of Chemistry and Biochemistry and Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0365
| | - J A McCammon
- Howard Hughes Medical Institute, Center for Theoretical Biological Physics, Department of Chemistry and Biochemistry and Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0365
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79
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Cumberworth A, Bui JM, Gsponer J. Free energies of solvation in the context of protein folding: Implications for implicit and explicit solvent models. J Comput Chem 2015; 37:629-40. [DOI: 10.1002/jcc.24235] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 09/25/2015] [Accepted: 10/06/2015] [Indexed: 12/13/2022]
Affiliation(s)
| | | | - Jörg Gsponer
- Center for High-Throughput Biology, UBC; Vancouver Canada
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80
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Mills EA, Plotkin SS. Protein Transfer Free Energy Obeys Entropy-Enthalpy Compensation. J Phys Chem B 2015; 119:14130-44. [DOI: 10.1021/acs.jpcb.5b09219] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Eric A. Mills
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
| | - Steven S. Plotkin
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada
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81
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Wang B, Wei GW. Parameter optimization in differential geometry based solvation models. J Chem Phys 2015; 143:134119. [PMID: 26450304 PMCID: PMC4602332 DOI: 10.1063/1.4932342] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 09/22/2015] [Indexed: 01/01/2023] Open
Abstract
Differential geometry (DG) based solvation models are a new class of variational implicit solvent approaches that are able to avoid unphysical solvent-solute boundary definitions and associated geometric singularities, and dynamically couple polar and non-polar interactions in a self-consistent framework. Our earlier study indicates that DG based non-polar solvation model outperforms other methods in non-polar solvation energy predictions. However, the DG based full solvation model has not shown its superiority in solvation analysis, due to its difficulty in parametrization, which must ensure the stability of the solution of strongly coupled nonlinear Laplace-Beltrami and Poisson-Boltzmann equations. In this work, we introduce new parameter learning algorithms based on perturbation and convex optimization theories to stabilize the numerical solution and thus achieve an optimal parametrization of the DG based solvation models. An interesting feature of the present DG based solvation model is that it provides accurate solvation free energy predictions for both polar and non-polar molecules in a unified formulation. Extensive numerical experiment demonstrates that the present DG based solvation model delivers some of the most accurate predictions of the solvation free energies for a large number of molecules.
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Affiliation(s)
- Bao Wang
- Department of Mathematics, Michigan State University, East Lansing, Michigan 48824, USA
| | - G W Wei
- Department of Mathematics, Michigan State University, East Lansing, Michigan 48824, USA
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82
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Choi H, Kang H, Park H. Computational Prediction of Molecular Hydration Entropy with Hybrid Scaled Particle Theory and Free-Energy Perturbation Method. J Chem Theory Comput 2015; 11:4933-42. [DOI: 10.1021/acs.jctc.5b00325] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hwanho Choi
- Department
of Bioscience and Biotechnology, Sejong University, 209 Neungdong-ro, Kwangjin-gu, Seoul 143-747, Korea
| | - Hongsuk Kang
- Institute
for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, United States
| | - Hwangseo Park
- Department
of Bioscience and Biotechnology, Sejong University, 209 Neungdong-ro, Kwangjin-gu, Seoul 143-747, Korea
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83
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Harris RC, Pettitt BM. Examining the assumptions underlying continuum-solvent models. J Chem Theory Comput 2015; 11:4593-600. [PMID: 26574250 DOI: 10.1021/acs.jctc.5b00684] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Continuum-solvent models (CSMs) have successfully predicted many quantities, including the solvation-free energies (ΔG) of small molecules, but they have not consistently succeeded at reproducing experimental binding free energies (ΔΔG), especially for protein-protein complexes. Several CSMs break ΔG into the free energy (ΔGvdw) of inserting an uncharged molecule into solution and the free energy (ΔGel) gained from charging. Some further divide ΔGvdw into the free energy (ΔGrep) of inserting a nearly hard cavity into solution and the free energy (ΔGatt) gained from turning on dispersive interactions between the solute and solvent. We show that for 9 protein-protein complexes neither ΔGrep nor ΔGvdw was linear in the solvent-accessible area A, as assumed in many CSMs, and the corresponding components of ΔΔG were not linear in changes in A. We show that linear response theory (LRT) yielded good estimates of ΔGatt and ΔΔGatt, but estimates of ΔΔGatt obtained from either the initial or final configurations of the solvent were not consistent with those from LRT. The LRT estimates of ΔGel differed by more than 100 kcal/mol from the explicit solvent model's (ESM's) predictions, and its estimates of the corresponding component (ΔΔGel) of ΔΔG differed by more than 10 kcal/mol. Finally, the Poisson-Boltzmann equation produced estimates of ΔGel that were correlated with those from the ESM, but its estimates of ΔΔGel were much less so. These findings may help explain why many CSMs have not been consistently successful at predicting ΔΔG for many complexes, including protein-protein complexes.
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Affiliation(s)
- Robert C Harris
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
| | - B Montgomery Pettitt
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
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84
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Harris RC, Drake JA, Pettitt BM. Multibody correlations in the hydrophobic solvation of glycine peptides. J Chem Phys 2015; 141:22D525. [PMID: 25494796 DOI: 10.1063/1.4901886] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Protein collapse during folding is often assumed to be driven by a hydrophobic solvation energy (ΔGvdw) that scales linearly with solvent-accessible surface area (A). In a previous study, we argued that ΔGvdw, as well as its attractive (ΔGatt) and repulsive (ΔGrep) components, was not simply a linear function of A. We found that the surface tensions, γrep, γatt, and γvdw, gotten from ΔGrep, ΔGatt, and ΔGvdw against A for four configurations of deca-alanine differed from those obtained for a set of alkanes. In the present study, we extend our analysis to fifty decaglycine structures and atomic decompositions. We find that different configurations of decaglycine generate different estimates of γrep. Additionally, we considered the reconstruction of the solvation free energy from scaling the free energy of solvation of each atom type, free in solution. The free energy of the isolated atoms, scaled by the inverse surface area the atom would expose in the molecule does not reproduce the γrep for the intact decaglycines. Finally, γatt for the decaglycine conformations is much larger in magnitude than those for deca-alanine or the alkanes, leading to large negative values of γvdw (-74 and -56 cal/mol/Å(2) for CHARMM27 and AMBER ff12sb force fields, respectively). These findings imply that ΔGvdw favors extended rather than compact structures for decaglycine. We find that ΔGrep and ΔGvdw have complicated dependencies on multibody correlations between solute atoms, on the geometry of the molecular surface, and on the chemical identities of the atoms.
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Affiliation(s)
- Robert C Harris
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Blvd, Galveston, Texas 77555-0304, USA
| | - Justin A Drake
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Blvd, Galveston, Texas 77555-0304, USA
| | - B Montgomery Pettitt
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, 301 University Blvd, Galveston, Texas 77555-0304, USA
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85
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Ratkova EL, Palmer DS, Fedorov MV. Solvation thermodynamics of organic molecules by the molecular integral equation theory: approaching chemical accuracy. Chem Rev 2015; 115:6312-56. [PMID: 26073187 DOI: 10.1021/cr5000283] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Ekaterina L Ratkova
- †G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Akademicheskaya Street 1, Ivanovo 153045, Russia.,‡The Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, Leipzig 04103, Germany
| | - David S Palmer
- ‡The Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, Leipzig 04103, Germany.,§Department of Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, Scotland G1 1XL, United Kingdom
| | - Maxim V Fedorov
- ‡The Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, Leipzig 04103, Germany.,∥Department of Physics, Scottish Universities Physics Alliance (SUPA), University of Strathclyde, John Anderson Building, 107 Rottenrow East, Glasgow G4 0NG, United Kingdom
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86
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Abstract
Processes ranging from oil-water phase separation to the formation of solid clathrate hydrates send mixed messages regarding whether oil molecules hate or love to be surrounded by water. Recent experimental and theoretical results help decipher these mixed messages by illuminating the conditions under which the stability of a hydrophobic contact is expected to exceed thermal energy fluctuations - thus facilitating hydrophobic self-assembly and the emergence of structure from randomness. Important open questions remain regarding the dependence of hydrophobic interactions on molecular size and temperature, as well as the balance of direct and water-mediated interactions.
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Affiliation(s)
- Dor Ben-Amotz
- Purdue University, Department of Chemistry, West Lafayette, Indiana 47907, United States
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87
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Liu M, Besford QA, Mulvaney T, Gray-Weale A. Order and correlation contributions to the entropy of hydrophobic solvation. J Chem Phys 2015; 142:114117. [PMID: 25796241 DOI: 10.1063/1.4908532] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The entropy of hydrophobic solvation has been explained as the result of ordered solvation structures, of hydrogen bonds, of the small size of the water molecule, of dispersion forces, and of solvent density fluctuations. We report a new approach to the calculation of the entropy of hydrophobic solvation, along with tests of and comparisons to several other methods. The methods are assessed in the light of the available thermodynamic and spectroscopic information on the effects of temperature on hydrophobic solvation. Five model hydrophobes in SPC/E water give benchmark solvation entropies via Widom's test-particle insertion method, and other methods and models are tested against these particle-insertion results. Entropies associated with distributions of tetrahedral order, of electric field, and of solvent dipole orientations are examined. We find these contributions are small compared to the benchmark particle-insertion entropy. Competitive with or better than other theories in accuracy, but with no free parameters, is the new estimate of the entropy contributed by correlations between dipole moments. Dipole correlations account for most of the hydrophobic solvation entropy for all models studied and capture the distinctive temperature dependence seen in thermodynamic and spectroscopic experiments. Entropies based on pair and many-body correlations in number density approach the correct magnitudes but fail to describe temperature and size dependences, respectively. Hydrogen-bond definitions and free energies that best reproduce entropies from simulations are reported, but it is difficult to choose one hydrogen bond model that fits a variety of experiments. The use of information theory, scaled-particle theory, and related methods is discussed briefly. Our results provide a test of the Frank-Evans hypothesis that the negative solvation entropy is due to structured water near the solute, complement the spectroscopic detection of that solvation structure by identifying the structural feature responsible for the entropy change, and point to a possible explanation for the observed dependence on length scale. Our key results are that the hydrophobic effect, i.e. the signature, temperature-dependent, solvation entropy of nonpolar molecules in water, is largely due to a dispersion force arising from correlations between rotating permanent dipole moments, that the strength of this force depends on the Kirkwood g-factor, and that the strength of this force may be obtained exactly without simulation.
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Affiliation(s)
- Maoyuan Liu
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
| | | | - Thomas Mulvaney
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
| | - Angus Gray-Weale
- School of Chemistry, The University of Melbourne, Victoria 3010, Australia
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88
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Colussi F, Sørensen TH, Alasepp K, Kari J, Cruys-Bagger N, Windahl MS, Olsen JP, Borch K, Westh P. Probing substrate interactions in the active tunnel of a catalytically deficient cellobiohydrolase (Cel7). J Biol Chem 2014; 290:2444-54. [PMID: 25477511 DOI: 10.1074/jbc.m114.624163] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellobiohydrolases break down cellulose sequentially by sliding along the crystal surface with a single cellulose strand threaded through the catalytic tunnel of the enzyme. This so-called processive mechanism relies on a complex pattern of enzyme-substrate interactions, which need to be addressed in molecular descriptions of processivity and its driving forces. Here, we have used titration calorimetry to study interactions of cellooligosaccharides (COS) and a catalytically deficient variant (E212Q) of the enzyme Cel7A from Trichoderma reesei. This enzyme has ∼10 glucopyranose subsites in the catalytic tunnel, and using COS ligands with a degree of polymerization (DP) from 2 to 8, different regions of the tunnel could be probed. For COS ligands with a DP of 2-3 the binding constants were around 10(5) m(-1), and for longer ligands (DP 5-8) this value was ∼10(7) m(-1). Within each of these groups we did not find increased affinity as the ligands got longer and potentially filled more subsites. On the contrary, we found a small but consistent affinity loss as DP rose from 6 to 8, particularly at the higher investigated temperatures. Other thermodynamic functions (ΔH, ΔS, and ΔCp) decreased monotonously with both temperature and DP. Combined interpretation of these thermodynamic results and previously published structural data allowed assessment of an affinity profile along the length axis of the active tunnel.
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Affiliation(s)
- Francieli Colussi
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Trine H Sørensen
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Kadri Alasepp
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Jeppe Kari
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Nicolaj Cruys-Bagger
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Michael S Windahl
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and Novozymes A/S, Krogshøjvej 36, DK-2880, Bagsværd, Denmark
| | - Johan P Olsen
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
| | - Kim Borch
- Novozymes A/S, Krogshøjvej 36, DK-2880, Bagsværd, Denmark
| | - Peter Westh
- From the Roskilde University, NSM, Research Unit for Functional Biomaterials, 1 Universitetsvej, Building 28, DK-4000 Denmark and
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89
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Mondal J, Friesner RA, Berne BJ. Role of Desolvation in Thermodynamics and Kinetics of Ligand Binding to a Kinase. J Chem Theory Comput 2014; 10:5696-5705. [PMID: 25516727 PMCID: PMC4263462 DOI: 10.1021/ct500584n] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Indexed: 12/29/2022]
Abstract
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Computer
simulations are used to determine the free energy landscape
for the binding of the anticancer drug Dasatinib to its src kinase
receptor and show that before settling into a free energy basin the
ligand must surmount a free energy barrier. An analysis based on using
both the ligand-pocket separation and the pocket-water occupancy as
reaction coordinates shows that the free energy barrier is a result
of the free energy cost for almost complete desolvation of the binding
pocket. The simulations further show that the barrier is not a result
of the reorganization free energy of the binding pocket. Although
a continuum solvent model gives the location of free energy minima,
it is not able to reproduce the intermediate free energy barrier.
Finally, it is shown that a kinetic model for the on rate constant
in which the ligand diffuses up to a doorway state and then surmounts
the desolvation free energy barrier is consistent with published microsecond
time-scale simulations of the ligand binding kinetics for this system
[Shaw, D. E. et al. J. Am.
Chem. Soc.2011, 133, 9181−918321545110].
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Affiliation(s)
- Jagannath Mondal
- Department of Chemistry, Columbia University , 3000 Broadway, New York, New York 10027, United States
| | - Richard A Friesner
- Department of Chemistry, Columbia University , 3000 Broadway, New York, New York 10027, United States
| | - B J Berne
- Department of Chemistry, Columbia University , 3000 Broadway, New York, New York 10027, United States
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90
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Abstract
Inserting an uncharged van der Waals (vdw) cavity into water disrupts the distribution of water and creates attractive dispersion interactions between the solvent and solute. This free-energy change is the hydrophobic solvation energy (ΔG(vdw)). Frequently, it is assumed to be linear in the solvent-accessible surface area, with a positive surface tension (γ) that is independent of the properties of the molecule. However, we found that γ for a set of alkanes differed from that for four configurations of decaalanine, and γ = -5 was negative for the decaalanines. These findings conflict with the notion that ΔG(vdw) favors smaller A. We broke ΔG(vdw) into the free energy required to exclude water from the vdw cavity (ΔG(rep)) and the free energy of forming the attractive interactions between the solute and solvent (ΔG(att)) and found that γ < 0 for the decaalanines because -γ(att) > γ(rep) and γ(att) < 0. Additionally, γ(att) and γ(rep) for the alkanes differed from those for the decaalanines, implying that none of ΔG(att), ΔG(rep), and ΔG(vdw) can be computed with a constant surface tension. We also showed that ΔG(att) could not be computed from either the initial or final water distributions, implying that this quantity is more difficult to compute than is sometimes assumed. Finally, we showed that each atom's contribution to γ(rep) depended on multibody interactions with its surrounding atoms, implying that these contributions are not additive. These findings call into question some hydrophobic models.
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91
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Drechsel NJD, Fennell CJ, Dill KA, Villà-Freixa J. TRIFORCE: Tessellated Semianalytical Solvent Exposed Surface Areas and Derivatives. J Chem Theory Comput 2014; 10:4121-4132. [PMID: 25221446 PMCID: PMC4159216 DOI: 10.1021/ct5002818] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Indexed: 12/01/2022]
Abstract
We present a new approach to the calculation of solvent-accessible surface areas of molecules with potential application to surface area based methods for determination of solvation free energies. As in traditional analytical and statistical approaches, this new algorithm, called TRIFORCE, reports both component areas and derivatives as a function of the atomic coordinates and radii. Unique to TRIFORCE are the rapid and scalable approaches for the determination of sphere intersection points and numerical estimation of the surface areas, derivatives, and other properties that can be associated with the surface area facets. The algorithm performs a special tessellation and semianalytical integration that uses a precomputed look-up table. This provides a simple way to balance numerical accuracy and memory usage. TRIFORCE calculates derivatives in the same manner, enabling application in force-dependent activities such as molecular geometry minimization. TRIFORCE is available free of charge for academic purposes as both a C++ library, which can be directly interfaced to existing molecular simulation packages, and a web-accessible application.
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Affiliation(s)
- Nils J. D. Drechsel
- Computational
Biochemistry and Biophysics Laboratory,
Research Unit on Biomedical Informatics, Universitat Pompeu Fabra, C/Doctor Aiguader, 88, 08003 Barcelona, Catalunya, Spain
- Laufer
Center for Physical and Quantitative Biology, Stony Brook University, Stony
Brook, New York 11794-5252, United States
- Department
of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Christopher J. Fennell
- Department
of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Ken A. Dill
- Laufer
Center for Physical and Quantitative Biology and Departments of Physics
and Chemistry, Stony Brook University, Stony Brook, New York 11794-5252, United States
| | - Jordi Villà-Freixa
- Computational
Biochemistry and Biophysics Laboratory,
Research Unit on Biomedical Informatics, Universitat Pompeu Fabra, C/Doctor Aiguader, 88, 08003 Barcelona, Catalunya, Spain
- Escola
Politècnica Superior, Universitat
de Vic—Universitat Central de Catalunya, C/de la Laura, 13, 08500 Vic, Catalunya, Spain
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92
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Schönbeck C, Westh P, Holm R. Complexation Thermodynamics of Modified Cyclodextrins: Extended Cavities and Distorted Structures. J Phys Chem B 2014; 118:10120-9. [DOI: 10.1021/jp506001j] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christian Schönbeck
- NSM,
Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark
- Biologics
and Pharmaceutical Science, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
- Department
of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- Sino-Danish Center for Education and Research (SDC), Niels Jensens Vej 2, DK-8000 Aarhus C, Denmark
| | - Peter Westh
- NSM,
Research Unit for Functional Biomaterials, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark
| | - René Holm
- Biologics
and Pharmaceutical Science, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
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93
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Nunes-Alves A, Arantes GM. Ligand-receptor affinities computed by an adapted linear interaction model for continuum electrostatics and by protein conformational averaging. J Chem Inf Model 2014; 54:2309-19. [PMID: 25076043 DOI: 10.1021/ci500301s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Accurate calculations of free energies involved in small-molecule binding to a receptor are challenging. Interactions between ligand, receptor, and solvent molecules have to be described precisely, and a large number of conformational microstates has to be sampled, particularly for ligand binding to a flexible protein. Linear interaction energy models are computationally efficient methods that have found considerable success in the prediction of binding free energies. Here, we parametrize a linear interaction model for implicit solvation with coefficients adapted by ligand and binding site relative polarities in order to predict ligand binding free energies. Results obtained for a diverse series of ligands suggest that the model has good predictive power and transferability. We also apply implicit ligand theory and propose approximations to average contributions of multiple ligand-receptor poses built from a protein conformational ensemble and find that exponential averages require proper energy discrimination between plausible binding poses and false-positives (i.e., decoys). The linear interaction model and the averaging procedures presented can be applied independently of each other and of the method used to obtain the receptor structural representation.
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Affiliation(s)
- Ariane Nunes-Alves
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo , Av. Prof. Lineu Prestes 748, 05508-900, São Paulo, SP, Brazil
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94
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Nakano M, Tateishi-Karimata H, Tanaka S, Sugimoto N. Affinity of Molecular Ions for DNA Structures Is Determined by Solvent-Accessible Surface Area. J Phys Chem B 2014; 118:9583-94. [DOI: 10.1021/jp505107g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
| | | | - Shigenori Tanaka
- Graduate
School of System Informatics, Department of Computational Science, Kobe University, 1-1, Rokkodai, Nada-ku, Kobe 657-8501, Japan
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95
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Daily MD, Chun J, Heredia-Langner A, Wei G, Baker NA. Origin of parameter degeneracy and molecular shape relationships in geometric-flow calculations of solvation free energies. J Chem Phys 2014; 139:204108. [PMID: 24289345 DOI: 10.1063/1.4832900] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Implicit solvent models are important tools for calculating solvation free energies for chemical and biophysical studies since they require fewer computational resources but can achieve accuracy comparable to that of explicit-solvent models. In past papers, geometric flow-based solvation models have been established for solvation analysis of small and large compounds. In the present work, the use of realistic experiment-based parameter choices for the geometric flow models is studied. We find that the experimental parameters of solvent internal pressure p = 172 MPa and surface tension γ = 72 mN/m produce solvation free energies within 1 RT of the global minimum root-mean-squared deviation from experimental data over the expanded set. Our results demonstrate that experimental values can be used for geometric flow solvent model parameters, thus eliminating the need for additional parameterization. We also examine the correlations between optimal values of p and γ which are strongly anti-correlated. Geometric analysis of the small molecule test set shows that these results are inter-connected with an approximately linear relationship between area and volume in the range of molecular sizes spanned by the data set. In spite of this considerable degeneracy between the surface tension and pressure terms in the model, both terms are important for the broader applicability of the model.
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Affiliation(s)
- Michael D Daily
- Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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96
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Vilseck J, Tirado-Rives J, Jorgensen WL. Evaluation of CM5 Charges for Condensed-Phase Modeling. J Chem Theory Comput 2014; 10:2802-2812. [PMID: 25061445 PMCID: PMC4095915 DOI: 10.1021/ct500016d] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Indexed: 11/30/2022]
Abstract
The recently developed Charge Model 5 (CM5) is tested for its utility in condensed-phase simulations. The CM5 approach, which derives partial atomic charges from Hirshfeld population analyses, provides excellent results for gas-phase dipole moments and is applicable to all elements of the periodic table. Herein, the adequacy of scaled CM5 charges for use in modeling aqueous solutions has been evaluated by computing free energies of hydration (ΔGhyd) for 42 neutral organic molecules via Monte Carlo statistical mechanics. An optimal scaling factor for the CM5 charges was determined to be 1.27, resulting in a mean unsigned error (MUE) of 1.1 kcal/mol for the free energies of hydration. Testing for an additional 20 molecules gave an MUE of 1.3 kcal/mol. The high precision of the results is confirmed by free energy calculations using both sequential perturbations and complete molecular annihilation. Performance for specific functional groups is discussed; sulfur-containing molecules yield the largest errors. In addition, the scaling factor of 1.27 is shown to be appropriate for CM5 charges derived from a variety of density functional methods and basis sets. Though the average errors from the 1.27*CM5 results are only slightly lower than those using 1.14*CM1A charges, the broader applicability and easier access to CM5 charges via the Gaussian program are additional attractive features. The 1.27*CM5 charge model can be used for an enormous variety of applications in conjunction with many fixed-charge force fields and molecular modeling programs.
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Affiliation(s)
- Jonah
Z. Vilseck
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Julian Tirado-Rives
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - William L. Jorgensen
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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97
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Graziano G. Comment on “Water’s Structure around Hydrophobic Solutes and the Iceberg Model”. J Phys Chem B 2014; 118:2598-9. [DOI: 10.1021/jp5008895] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Giuseppe Graziano
- Dipartimento di Scienze e Tecnologie, Università del Sannio, Via Port’Arsa
11, 82100 Benevento, Italy
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98
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Zahn R, Bickel KR, Zambelli T, Reichenbach J, Kuhn FM, Vörös J, Schuster R. The entropy of water in swelling PGA/PAH polyelectrolyte multilayers. SOFT MATTER 2014; 10:688-693. [PMID: 24835977 DOI: 10.1039/c3sm52489b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigated the thermodynamical properties of water exchanged in poly(l-glutamic acid)/poly(allylamine)hydrochloride (PGA/PAH) polyelectrolyte multilayers containing ferrocyanide. Oxidation/reduction of the ferrocyanide in the multilayer caused a reversible swelling/contraction of the film due to the uptake/release of counter ions and water. We used electrochemical quartz crystal microbalance and electrochemical microcalorimetry to correlate the amount of water with the accompanying entropy changes during electrochemical swelling of the multilayer for a series of different anions at different concentrations. The number of exchanged water molecules was highly dependent on the ionic strength and the type of anion in the buffer solution. However, the entropy change per exchanged water molecule was found to be independent of these two parameters. The water molecules in the polyelectrolyte multilayer have reduced the entropy compared to that of bulk water (≈-1 J mol(-1) K(-1)). A comparison of hydration entropies for free polyelectrolytes and PGA/PAH multilayers suggests that such systems are mainly stabilized by water release during multilayer construction.
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Affiliation(s)
- Raphael Zahn
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich, Switzerland.
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99
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Kokubo H, Harris RC, Asthagiri D, Pettitt BM. Solvation free energies of alanine peptides: the effect of flexibility. J Phys Chem B 2013; 117:16428-35. [PMID: 24328358 DOI: 10.1021/jp409693p] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electrostatic (ΔGel), van der Waals cavity-formation (ΔGvdw), and total (ΔG) solvation free energies for 10 alanine peptides ranging in length (n) from 1 to 10 monomers were calculated. The free energies were computed both with fixed, extended conformations of the peptides and again for some of the peptides without constraints. The solvation free energies, ΔGel, and components ΔGvdw, and ΔG, were found to be linear in n, with the slopes of the best-fit lines being γel, γvdw, and γ, respectively. Both γel and γ were negative for fixed and flexible peptides, and γvdw was negative for fixed peptides. That γvdw was negative was surprising, as experimental data on alkanes, theoretical models, and MD computations on small molecules and model systems generally suggest that γvdw should be positive. A negative γvdw seemingly contradicts the notion that ΔGvdw drives the initial collapse of the protein when it folds by favoring conformations with small surface areas. When we computed ΔGvdw for the flexible peptides, thereby allowing the peptides to assume natural ensembles of more compact conformations, γvdw was positive. Because most proteins do not assume extended conformations, a ΔGvdw that increases with increasing surface area may be typical for globular proteins. An alternative hypothesis is that the collapse is driven by intramolecular interactions. We find few intramolecular H-bonds but show that the intramolecular van der Waals interaction energy is more favorable for the flexible than for the extended peptides, seemingly favoring this hypothesis. The large fluctuations in the vdw energy may make attributing the collapse of the peptide to this intramolecular energy difficult.
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Affiliation(s)
- Hironori Kokubo
- Sealy Center for Structural Biology and Molecular Biophysics, Departments of Biochemistry and Molecular Biology and Pharmacology and Toxicology, University of Texas Medical Branch , 301 University Blvd, Galveston, Texas 77555-0304, United States
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100
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Chao MC, Weng NH, Chang HC, Jiang JC, Lin SH. High-Pressure and Concentration-Dependent Studies on C-H-O Interactions of Binary Aqueous Mixtures: Formic Acid/D2O and Acetone/D2O. J CHIN CHEM SOC-TAIP 2013. [DOI: 10.1002/jccs.200100090] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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