1
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Narayan B, Herbert C, Rodriguez BJ, Brooks BR, Buchete NV. Replica Exchange Molecular Dynamics of Diphenylalanine Amyloid Peptides in Electric Fields. J Phys Chem B 2021; 125:5233-5242. [PMID: 33990140 PMCID: PMC8279545 DOI: 10.1021/acs.jpcb.1c01939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The self-assembling propensity of amyloid peptides such as diphenylalanine (FF) allows them to form ordered, nanoscale structures, with biocompatible properties important for biomedical applications. Moreover, piezoelectric properties allow FF molecules and their aggregates (e.g., FF nanotubes) to be aligned in a controlled way by the application of external electric fields. However, while the behavior of FF nanostructures emerges from the biophysical properties of the monomers, the detailed responses of individual peptides to both temperature and electric fields are not fully understood. Here, we study the temperature-dependent conformational dynamics of FF peptides solvated in explicit water molecules, an environment relevant to biomedical applications, by using an enhanced sampling method, replica exchange molecular dynamics (REMD), in conjunction with applied electric fields. Our simulations highlight and overcome possible artifacts that may occur during the setup of REMD simulations of explicitly solvated peptides in the presence of external electric fields, a problem particularly important in the case of short peptides such as FF. The presence of the external fields could overstabilize certain conformational states in one or more REMD replicas, leading to distortions of the underlying potential energy distributions observed at each temperature. This can be overcome by correcting the REMD initial conditions to include the lower-energy conformations induced by the external field. We show that the converged REMD data can be analyzed using a Markovian description of conformational states and show that a rather complex, 3-state, temperature-dependent conformational dynamics in the absence of electric fields collapses to only one of these states in the presence of the electric fields. These details on the temperature- and electric-field-dependent thermodynamic and kinetic properties of small FF amyloid peptides can be useful in understanding and devising new methods to control their aggregation-prone biophysical properties and, possibly, the structural and biophysical properties of FF molecular nanostructures.
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Affiliation(s)
- Brajesh Narayan
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland.,Institute for Discovery, University College Dublin, Belfield, Dublin 4, Ireland
| | - Colm Herbert
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland.,Institute for Discovery, University College Dublin, Belfield, Dublin 4, Ireland
| | - Brian J Rodriguez
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland.,Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - Bernard R Brooks
- Laboratory of Computational Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Nicolae-Viorel Buchete
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland.,Institute for Discovery, University College Dublin, Belfield, Dublin 4, Ireland
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2
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Yang M, Tang Y, Weng J, Liu Z, Wang W. The Role of Calcium in Regulating the Conformational Dynamics of d-Galactose/d-Glucose-Binding Protein Revealed by Markov State Model Analysis. J Chem Inf Model 2021; 61:891-900. [PMID: 33445873 DOI: 10.1021/acs.jcim.0c01119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The d-glucose/d-galactose-binding protein (GGBP) from Escherichia coli is a substrate-binding protein (SBP) associated with sugar transport and chemotaxis. It is also a calcium-binding protein, which makes it unique in the SBP family. However, the functional importance of Ca2+ binding is not fully understood. Here, the calcium-dependent properties of GGBP were explored by all-atom molecular dynamics simulations and Markov state model (MSM) analysis as well as single-molecule Förster resonance energy transfer (smFRET) measurements. In agreement with previous experimental studies, we observed the structure stabilization effect of Ca2+ binding on the C-terminal domain of GGBP, especially the Ca2+-binding site. Interestingly, the MSMs of calcium-depleted GGBP and calcium-bound GGBP (GGBP/Ca2+) demonstrate that Ca2+ greatly stabilizes the open conformation, and smFRET measurements confirmed this result. Further analysis reveals that Ca2+ binding disturbs the local hydrogen bonding interactions and the conformational dynamics of the hinge region, thereby weakening the long-range interdomain correlations to favor the open conformation. These results suggest an active regulatory role of Ca2+ binding in GGBP, which finely tunes the conformational distribution. The work sheds new light on the study of calcium-binding proteins in prokaryotes.
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Affiliation(s)
- Maohua Yang
- Department of Chemistry, Multiscale Research Institute of Complex Systems and Institute of Biomedical Sciences, Fudan University, Shanghai 200438, China
| | - Yegen Tang
- Department of Chemistry, Multiscale Research Institute of Complex Systems and Institute of Biomedical Sciences, Fudan University, Shanghai 200438, China
| | - Jingwei Weng
- Department of Chemistry, Multiscale Research Institute of Complex Systems and Institute of Biomedical Sciences, Fudan University, Shanghai 200438, China
| | - Zhijun Liu
- National Facility for Protein Science in Shanghai, Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
| | - Wenning Wang
- Department of Chemistry, Multiscale Research Institute of Complex Systems and Institute of Biomedical Sciences, Fudan University, Shanghai 200438, China
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3
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Sharpe DJ, Wales DJ. Efficient and exact sampling of transition path ensembles on Markovian networks. J Chem Phys 2020; 153:024121. [DOI: 10.1063/5.0012128] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Daniel J. Sharpe
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - David J. Wales
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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4
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Wang D, Weng J, Wang W. Glycerol transport through the aquaglyceroporin GlpF: bridging dynamics and kinetics with atomic simulation. Chem Sci 2019; 10:6957-6965. [PMID: 31588262 PMCID: PMC6685356 DOI: 10.1039/c9sc01690b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Accepted: 06/17/2019] [Indexed: 11/21/2022] Open
Abstract
The aquaglyceroporin GlpF is a member of the aquaporin family. It selectively conducts small molecules, such as glycerol, across the cell membrane under a concentration gradient of the substrate. Atomistic molecular dynamics (MD) simulation would provide great insight into the substrate transport mechanism of GlpF and membrane channels alike. Ideally, non-equilibrium simulations under various concentration gradients of glycerol are desired to emulate the transportation in cells, but this kind of simulation is difficult due to a complicated system setup and high computational cost. Here, we present a new strategy to extract non-equilibrium kinetic information from equilibrium MD simulation. We first performed long-time (totally 22.5 μs) multi-copy equilibrium MD simulations of glycerol conduction through GlpF. Tens of times the spontaneous permeation of glycerol through GlpF was observed, allowing us to elucidate the detailed mechanism of the stereoselectivity for glycerol. Then we employed Markov state model (MSM) analysis of the MD trajectories to identify the intermediate states during glycerol transport and calculate the inter-state transition rate constants. Based on the results of MSM analysis, we built the kinetic models of glycerol transport and calculated the glycerol fluxes under various concentration gradients by solving the master equations. The results agree well with the experimental measurement at a certain glycerol concentration, and provide holistic information on the glycerol conduction capacity of GlpF. Our work demonstrates that long-time atomistic MD simulations can now bridge the microscopic dynamics and the kinetic description of substance transport through membrane channels, hopefully facilitating the engineering of new selective channels for various molecules.
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Affiliation(s)
- Dongdong Wang
- Department of Chemistry , Institutes of Biomedical Sciences , Multiscale Research Institute of Complex Systems , Fudan University , Shanghai , P. R. China . ;
| | - Jingwei Weng
- Department of Chemistry , Institutes of Biomedical Sciences , Multiscale Research Institute of Complex Systems , Fudan University , Shanghai , P. R. China . ;
| | - Wenning Wang
- Department of Chemistry , Institutes of Biomedical Sciences , Multiscale Research Institute of Complex Systems , Fudan University , Shanghai , P. R. China . ;
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5
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Bacci M, Caflisch A, Vitalis A. On the removal of initial state bias from simulation data. J Chem Phys 2019; 150:104105. [PMID: 30876362 DOI: 10.1063/1.5063556] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Classical atomistic simulations of biomolecules play an increasingly important role in molecular life science. The structure of current computing architectures favors methods that run multiple trajectories at once without requiring extensive communication between them. Many advanced sampling strategies in the field fit this mold. These approaches often rely on an adaptive logic and create ensembles of comparatively short trajectories whose starting points are not distributed according to the correct Boltzmann weights. This type of bias is notoriously difficult to remove, and Markov state models (MSMs) are one of the few strategies available for recovering the correct kinetics and thermodynamics from these ensembles of trajectories. In this contribution, we analyze the performance of MSMs in the thermodynamic reweighting task for a hierarchical set of systems. We show that MSMs can be rigorous tools to recover the correct equilibrium distribution for systems of sufficiently low dimensionality. This is conditional upon not tampering with local flux imbalances found in the data. For a real-world application, we find that a pure likelihood-based inference of the transition matrix produces the best results. The removal of the bias is incomplete, however, and for this system, all tested MSMs are outperformed by an alternative albeit less general approach rooted in the ideas of statistical resampling. We conclude by formulating some recommendations for how to address the reweighting issue in practice.
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Affiliation(s)
- Marco Bacci
- University of Zurich, Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Amedeo Caflisch
- University of Zurich, Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Andreas Vitalis
- University of Zurich, Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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6
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Narayan B, Herbert C, Yuan Y, Rodriguez BJ, Brooks BR, Buchete NV. Conformational analysis of replica exchange MD: Temperature-dependent Markov networks for FF amyloid peptides. J Chem Phys 2018; 149:072323. [PMID: 30134732 DOI: 10.1063/1.5027580] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Recent molecular modeling methods using Markovian descriptions of conformational states of biomolecular systems have led to powerful analysis frameworks that can accurately describe their complex dynamical behavior. In conjunction with enhanced sampling methods, such as replica exchange molecular dynamics (REMD), these frameworks allow the systematic and accurate extraction of transition probabilities between the corresponding states, in the case of Markov state models, and of statistically-optimized transition rates, in the case of the corresponding coarse master equations. However, applying automatically such methods to large molecular dynamics (MD) simulations, with explicit water molecules, remains limited both by the initial ability to identify good candidates for the underlying Markovian states and by the necessity to do so using good collective variables as reaction coordinates that allow the correct counting of inter-state transitions at various lag times. Here, we show that, in cases when representative molecular conformations can be identified for the corresponding Markovian states, and thus their corresponding collective evolution of atomic positions can be calculated along MD trajectories, one can use them to build a new type of simple collective variable, which can be particularly useful in both the correct state assignment and in the subsequent accurate counting of inter-state transition probabilities. In the case of the ubiquitously used root-mean-square deviation (RMSD) of atomic positions, we introduce the relative RMSD (RelRMSD) measure as a good reaction coordinate candidate. We apply this method to the analysis of REMD trajectories of amyloid-forming diphenylalanine (FF) peptides-a system with important nanotechnology and biomedical applications due to its self-assembling and piezoelectric properties-illustrating the use of RelRMSD in extracting its temperature-dependent intrinsic kinetics, without a priori assumptions on the functional form (e.g., Arrhenius or not) of the underlying conformational transition rates. The RelRMSD analysis enables as well a more objective assessment of the convergence of the REMD simulations. This type of collective variable may be generalized to other observables that could accurately capture conformational differences between the underlying Markov states (e.g., distance RMSD, the fraction of native contacts, etc.).
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Affiliation(s)
- Brajesh Narayan
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
| | - Colm Herbert
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
| | - Ye Yuan
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
| | - Brian J Rodriguez
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
| | - Bernard R Brooks
- Laboratory of Computational Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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7
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Leahy CT, Kells A, Hummer G, Buchete NV, Rosta E. Peptide dimerization-dissociation rates from replica exchange molecular dynamics. J Chem Phys 2018; 147:152725. [PMID: 29055328 DOI: 10.1063/1.5004774] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We show how accurate rates of formation and dissociation of peptide dimers can be calculated using direct transition counting (DTC) from replica-exchange molecular dynamics (REMD) simulations. First, continuous trajectories corresponding to system replicas evolving at different temperatures are used to assign conformational states. Second, we analyze the entire REMD data to calculate the corresponding rates at each temperature directly from the number of transition counts. Finally, we compare the kinetics extracted directly, using the DTC method, with indirect estimations based on trajectory likelihood maximization using short-time propagators and on decay rates of state autocorrelation functions. For systems with relatively low-dimensional intrinsic conformational dynamics, the DTC method is simple to implement and leads to accurate temperature-dependent rates. We apply the DTC rate-extraction method to all-atom REMD simulations of dimerization of amyloid-forming NNQQ tetrapetides in explicit water. In an assessment of the REMD sampling efficiency with respect to standard MD, we find a gain of more than a factor of two at the lowest temperature.
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Affiliation(s)
- Cathal T Leahy
- School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
| | - Adam Kells
- Department of Chemistry, King's College London, London SE1 1DB, United Kingdom
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | | | - Edina Rosta
- Department of Chemistry, King's College London, London SE1 1DB, United Kingdom
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8
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El Hage K, Mondal P, Meuwly M. Free energy simulations for protein ligand binding and stability. MOLECULAR SIMULATION 2018. [DOI: 10.1080/08927022.2017.1416115] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Krystel El Hage
- Department of Chemistry, University of Basel , Basel, Switzerland
| | - Padmabati Mondal
- Department of Chemistry, University of Basel , Basel, Switzerland
| | - Markus Meuwly
- Department of Chemistry, University of Basel , Basel, Switzerland
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9
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El Hage K, Brickel S, Hermelin S, Gaulier G, Schmidt C, Bonacina L, van Keulen SC, Bhattacharyya S, Chergui M, Hamm P, Rothlisberger U, Wolf JP, Meuwly M. Implications of short time scale dynamics on long time processes. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2017; 4:061507. [PMID: 29308419 PMCID: PMC5741438 DOI: 10.1063/1.4996448] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/15/2017] [Indexed: 05/02/2023]
Abstract
This review provides a comprehensive overview of the structural dynamics in topical gas- and condensed-phase systems on multiple length and time scales. Starting from vibrationally induced dissociation of small molecules in the gas phase, the question of vibrational and internal energy redistribution through conformational dynamics is further developed by considering coupled electron/proton transfer in a model peptide over many orders of magnitude. The influence of the surrounding solvent is probed for electron transfer to the solvent in hydrated I-. Next, the dynamics of a modified PDZ domain over many time scales is analyzed following activation of a photoswitch. The hydration dynamics around halogenated amino acid side chains and their structural dynamics in proteins are relevant for iodinated TyrB26 insulin. Binding of nitric oxide to myoglobin is a process for which experimental and computational analyses have converged to a common view which connects rebinding time scales and the underlying dynamics. Finally, rhodopsin is a paradigmatic system for multiple length- and time-scale processes for which experimental and computational methods provide valuable insights into the functional dynamics. The systems discussed here highlight that for a comprehensive understanding of how structure, flexibility, energetics, and dynamics contribute to functional dynamics, experimental studies in multiple wavelength regions and computational studies including quantum, classical, and more coarse grained levels are required.
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Affiliation(s)
- Krystel El Hage
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Sebastian Brickel
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
| | - Sylvain Hermelin
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Geoffrey Gaulier
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Cédric Schmidt
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Luigi Bonacina
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Siri C van Keulen
- Institute of Chemical Sciences and Engineering, EPFL, Lausanne, Switzerland
| | | | - Majed Chergui
- Institute of Chemical Sciences and Engineering, EPFL, Lausanne, Switzerland
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | | | - Jean-Pierre Wolf
- Department of Applied Physics (GAP), University of Geneva, 22 Ch. de Pinchat, 1211 Geneva 4, Switzerland
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland
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10
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Liao Q, Owen MC, Olubiyi OO, Barz B, Strodel B. Conformational Transitions of the Amyloid-β Peptide Upon Copper(II) Binding and pH Changes. Isr J Chem 2017. [DOI: 10.1002/ijch.201600108] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Qinghua Liao
- Institute of Complex Systems: Structural Biochemistry (ICS-6); Forschungszentrum Jülich GmbH; 52425 Jülich Germany
| | - Michael C. Owen
- Institute of Complex Systems: Structural Biochemistry (ICS-6); Forschungszentrum Jülich GmbH; 52425 Jülich Germany
| | - Olujide O. Olubiyi
- Department of Pharmacology and Therapeutics; College of Medicine and Health Sciences; Afe Babalola University; Nigeria
| | - Bogdan Barz
- Institute of Complex Systems: Structural Biochemistry (ICS-6); Forschungszentrum Jülich GmbH; 52425 Jülich Germany
- Institute of Theoretical and Computational Chemistry; Heinrich Heine University Düsseldorf; 40225 Düsseldorf Germany
| | - Birgit Strodel
- Institute of Complex Systems: Structural Biochemistry (ICS-6); Forschungszentrum Jülich GmbH; 52425 Jülich Germany
- Institute of Theoretical and Computational Chemistry; Heinrich Heine University Düsseldorf; 40225 Düsseldorf Germany
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11
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Leahy CT, Murphy RD, Hummer G, Rosta E, Buchete NV. Coarse Master Equations for Binding Kinetics of Amyloid Peptide Dimers. J Phys Chem Lett 2016; 7:2676-2682. [PMID: 27323250 DOI: 10.1021/acs.jpclett.6b00518] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We characterize the kinetics of dimer formation of the short amyloid microcrystal-forming tetrapeptides NNQQ by constructing coarse master equations for the conformational dynamics of the system, using temperature replica-exchange molecular dynamics (REMD) simulations. We minimize the effects of Kramers-type recrossings by assigning conformational states based on their sequential time evolution. Transition rates are further estimated from short-time state propagators by maximizing the likelihood that the extracted rates agree with the observed atomistic trajectories without any a priori assumptions about their temperature dependence. Here, we evaluate the rates for both continuous replica trajectories that visit different temperatures and for discontinuous data corresponding to each REMD temperature. While the binding-unbinding kinetic process is clearly Markovian, the conformational dynamics of the bound NNQQ dimer has a complex character. Our kinetic analysis allows us to discriminate between short-lived encounter pairs and strongly bound conformational states. The conformational dynamics of NNQQ dimers supports a kinetically driven aggregation mechanism, in agreement with the polymorphic character reported for amyloid aggregates such as microcrystals and fibrils.
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Affiliation(s)
- Cathal T Leahy
- School of Physics, University College Dublin , Belfield, Dublin 4, Ireland
- Complex and Adaptive Systems Laboratory, University College Dublin , Belfield, Dublin 4, Ireland
| | - Ronan D Murphy
- School of Physics, University College Dublin , Belfield, Dublin 4, Ireland
- Complex and Adaptive Systems Laboratory, University College Dublin , Belfield, Dublin 4, Ireland
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics , Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany
| | - Edina Rosta
- Department of Chemistry, King's College London , London SE1 1DB, United Kingdom
| | - Nicolae-Viorel Buchete
- School of Physics, University College Dublin , Belfield, Dublin 4, Ireland
- Complex and Adaptive Systems Laboratory, University College Dublin , Belfield, Dublin 4, Ireland
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12
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Zhang BW, Dai W, Gallicchio E, He P, Xia J, Tan Z, Levy RM. Simulating Replica Exchange: Markov State Models, Proposal Schemes, and the Infinite Swapping Limit. J Phys Chem B 2016; 120:8289-301. [PMID: 27079355 DOI: 10.1021/acs.jpcb.6b02015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Replica exchange molecular dynamics is a multicanonical simulation technique commonly used to enhance the sampling of solvated biomolecules on rugged free energy landscapes. While replica exchange is relatively easy to implement, there are many unanswered questions about how to use this technique most efficiently, especially because it is frequently the case in practice that replica exchange simulations are not fully converged. A replica exchange cycle consists of a series of molecular dynamics steps of a set of replicas moving under different Hamiltonians or at different thermodynamic states followed by one or more replica exchange attempts to swap replicas among the different states. How the replica exchange cycle is constructed affects how rapidly the system equilibrates. We have constructed a Markov state model of replica exchange (MSMRE) using long molecular dynamics simulations of a host-guest binding system as an example, in order to study how different implementations of the replica exchange cycle can affect the sampling efficiency. We analyze how the number of replica exchange attempts per cycle, the number of MD steps per cycle, and the interaction between the two parameters affects the largest implied time scale of the MSMRE simulation. The infinite swapping limit is an important concept in replica exchange. We show how to estimate the infinite swapping limit from the diagonal elements of the exchange transition matrix constructed from MSMRE "simulations of simulations" as well as from relatively short runs of the actual replica exchange simulations.
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Affiliation(s)
- Bin W Zhang
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University , Philadelphia, Pennsylvania 19122, United States
| | - Wei Dai
- Department of Physics and Astronomy, Rutgers, the State University of New Jersey , Piscataway, New Jersey 08854, United States
| | - Emilio Gallicchio
- Department of Chemistry, Brooklyn College of the City University of New York , Brooklyn, New York 11210, United States
| | - Peng He
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University , Philadelphia, Pennsylvania 19122, United States
| | - Junchao Xia
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University , Philadelphia, Pennsylvania 19122, United States
| | - Zhiqiang Tan
- Department of Statistics, Rutgers, the State University of New Jersey , Piscataway, New Jersey 08854, United States
| | - Ronald M Levy
- Center for Biophysics and Computational Biology, Department of Chemistry and Institute for Computational Molecular Science, Temple University , Philadelphia, Pennsylvania 19122, United States
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13
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Suárez E, Pratt AJ, Chong LT, Zuckerman DM. Estimating first-passage time distributions from weighted ensemble simulations and non-Markovian analyses. Protein Sci 2016; 25:67-78. [PMID: 26131764 PMCID: PMC4815309 DOI: 10.1002/pro.2738] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 06/23/2015] [Accepted: 06/24/2015] [Indexed: 01/17/2023]
Abstract
First-passage times (FPTs) are widely used to characterize stochastic processes such as chemical reactions, protein folding, diffusion processes or triggering a stock option. In previous work (Suarez et al., JCTC 2014;10:2658-2667), we demonstrated a non-Markovian analysis approach that, with a sufficient subset of history information, yields unbiased mean first-passage times from weighted-ensemble (WE) simulations. The estimation of the distribution of the first-passage times is, however, a more ambitious goal since it cannot be obtained by direct observation in WE trajectories. Likewise, a large number of events would be required to make a good estimation of the distribution from a regular "brute force" simulation. Here, we show how the previously developed non-Markovian analysis can generate approximate, but highly accurate, FPT distributions from WE data. The analysis can also be applied to any other unbiased trajectories, such as from standard molecular dynamics simulations. The present study employs a range of systems with independent verification of the distributions to demonstrate the success and limitations of the approach. By comparison to a standard Markov analysis, the non-Markovian approach is less sensitive to the user-defined discretization of configuration space.
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Affiliation(s)
- Ernesto Suárez
- Department of Computational and Systems Biology, University of Pittsburgh, Pennsylvania
| | - Adam J Pratt
- Department of Chemistry, University of Pittsburgh, Pennsylvania
| | - Lillian T Chong
- Department of Chemistry, University of Pittsburgh, Pennsylvania
| | - Daniel M Zuckerman
- Department of Computational and Systems Biology, University of Pittsburgh, Pennsylvania
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14
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Kukic P, Kannan A, Dijkstra MJJ, Abeln S, Camilloni C, Vendruscolo M. Mapping the Protein Fold Universe Using the CamTube Force Field in Molecular Dynamics Simulations. PLoS Comput Biol 2015; 11:e1004435. [PMID: 26505754 PMCID: PMC4624779 DOI: 10.1371/journal.pcbi.1004435] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Accepted: 07/06/2015] [Indexed: 12/02/2022] Open
Abstract
It has been recently shown that the coarse-graining of the structures of polypeptide chains as self-avoiding tubes can provide an effective representation of the conformational space of proteins. In order to fully exploit the opportunities offered by such a ‘tube model’ approach, we present here a strategy to combine it with molecular dynamics simulations. This strategy is based on the incorporation of the ‘CamTube’ force field into the Gromacs molecular dynamics package. By considering the case of a 60-residue polyvaline chain, we show that CamTube molecular dynamics simulations can comprehensively explore the conformational space of proteins. We obtain this result by a 20 μs metadynamics simulation of the polyvaline chain that recapitulates the currently known protein fold universe. We further show that, if residue-specific interaction potentials are added to the CamTube force field, it is possible to fold a protein into a topology close to that of its native state. These results illustrate how the CamTube force field can be used to explore efficiently the universe of protein folds with good accuracy and very limited computational cost. Modelling protein behaviour using computer simulations has progressively emerged in the last 50 years as a powerful strategy in structural and molecular biology. Over this period there has been a continuing interest in pushing the boundaries of this approach in terms of the size of the systems and the timescale of the processes that can be studied. Coarse-grained models offer in principle great opportunities in this context, but it has been extremely challenging to obtain force fields of accuracy comparable to that typical of fully atomistic models. We show here that the representation of protein molecules as self-avoiding tubes within the CamTube model enables the comprehensive, accurate and very fast exploration of the conformational space of proteins in molecular dynamics simulations. We illustrate in particular how the comprehensive mapping of the protein fold universe obtained using the CamTube model offers the possibility of analysing the behaviour of proteins in a wide range of non-native states.
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Affiliation(s)
- Predrag Kukic
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Arvind Kannan
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- Departments of Bioengineering, Stanford University, Stanford, California, United States of America
| | - Maurits J. J. Dijkstra
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- Department of Computer Science, Vrije Universiteit, Amsterdam, The Netherlands
| | - Sanne Abeln
- Department of Computer Science, Vrije Universiteit, Amsterdam, The Netherlands
| | - Carlo Camilloni
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Michele Vendruscolo
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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15
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Cazade PA, Zheng W, Prada-Gracia D, Berezovska G, Rao F, Clementi C, Meuwly M. A comparative analysis of clustering algorithms: O2 migration in truncated hemoglobin I from transition networks. J Chem Phys 2015; 142:025103. [PMID: 25591387 DOI: 10.1063/1.4904431] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The ligand migration network for O2-diffusion in truncated Hemoglobin N is analyzed based on three different clustering schemes. For coordinate-based clustering, the conventional k-means and the kinetics-based Markov Clustering (MCL) methods are employed, whereas the locally scaled diffusion map (LSDMap) method is a collective-variable-based approach. It is found that all three methods agree well in their geometrical definition of the most important docking site, and all experimentally known docking sites are recovered by all three methods. Also, for most of the states, their population coincides quite favourably, whereas the kinetics of and between the states differs. One of the major differences between k-means and MCL clustering on the one hand and LSDMap on the other is that the latter finds one large primary cluster containing the Xe1a, IS1, and ENT states. This is related to the fact that the motion within the state occurs on similar time scales, whereas structurally the state is found to be quite diverse. In agreement with previous explicit atomistic simulations, the Xe3 pocket is found to be a highly dynamical site which points to its potential role as a hub in the network. This is also highlighted in the fact that LSDMap cannot identify this state. First passage time distributions from MCL clusterings using a one- (ligand-position) and two-dimensional (ligand-position and protein-structure) descriptor suggest that ligand- and protein-motions are coupled. The benefits and drawbacks of the three methods are discussed in a comparative fashion and highlight that depending on the questions at hand the best-performing method for a particular data set may differ.
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Affiliation(s)
- Pierre-André Cazade
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Wenwei Zheng
- Department of Chemistry, Rice University, 6100 Main St., Houston, Texas 77005, USA
| | - Diego Prada-Gracia
- School of Soft Matter Research, Freiburg Institute for Advanced Studies, Albertstrasse 19, 79104 Freiburg im Breisgau, Germany
| | - Ganna Berezovska
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Francesco Rao
- School of Soft Matter Research, Freiburg Institute for Advanced Studies, Albertstrasse 19, 79104 Freiburg im Breisgau, Germany
| | - Cecilia Clementi
- Department of Chemistry, Rice University, 6100 Main St., Houston, Texas 77005, USA
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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16
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Nam GM, Makarov DE. Extracting intrinsic dynamic parameters of biomolecular folding from single-molecule force spectroscopy experiments. Protein Sci 2015; 25:123-34. [PMID: 26088347 DOI: 10.1002/pro.2727] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 06/17/2015] [Accepted: 06/17/2015] [Indexed: 11/12/2022]
Abstract
Single-molecule studies in which a mechanical force is transmitted to the molecule of interest and the molecular extension or position is monitored as a function of time are versatile tools for probing the dynamics of protein folding, stepping of molecular motors, and other biomolecular processes involving activated barrier crossing. One complication in interpreting such studies, however, is the fact that the typical size of a force probe (e.g., a dielectric bead in optical tweezers or the atomic force microscope tip/cantilever assembly) is much larger than the molecule itself, and so the observed molecular motion is affected by the hydrodynamic drag on the probe. This presents the experimenter with a nontrivial task of deconvolving the intrinsic molecular parameters, such as the intrinsic free energy barrier and the effective diffusion coefficient exhibited while crossing the barrier from the experimental signal. Here we focus on the dynamical aspect of this task and show how the intrinsic diffusion coefficient along the molecular reaction coordinate can be inferred from single-molecule measurements of the rates of biomolecular folding and unfolding. We show that the feasibility of accomplishing this task is strongly dependent on the relationship between the intrinsic molecular elasticity and that of the linker connecting the molecule to the force probe and identify the optimal range of instrumental parameters allowing determination of instrument-free molecular dynamics.
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Affiliation(s)
- Gi-Moon Nam
- Department of Chemistry, University of Texas at Austin, Austin, Texas, 78712
| | - Dmitrii E Makarov
- Department of Chemistry, University of Texas at Austin, Austin, Texas, 78712.,Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas, 78712
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17
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Han W, Schulten K. Fibril elongation by Aβ(17-42): kinetic network analysis of hybrid-resolution molecular dynamics simulations. J Am Chem Soc 2014; 136:12450-60. [PMID: 25134066 PMCID: PMC4156860 DOI: 10.1021/ja507002p] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
![]()
A critical step of β-amyloid
fibril formation is fibril elongation
in which amyloid-β monomers undergo structural transitions to
fibrillar structures upon their binding to fibril tips. The atomic
detail of the structural transitions remains poorly understood. Computational
characterization of the structural transitions is limited so far to
short Aβ segments (5–10 aa) owing to the long time scale
of Aβ fibril elongation. To overcome the computational time
scale limit, we combined a hybrid-resolution model with umbrella sampling
and replica exchange molecular dynamics and performed altogether ∼1.3
ms of molecular dynamics simulations of fibril elongation for Aβ17–42. Kinetic network analysis of biased simulations
resulted in a kinetic model that encompasses all Aβ segments
essential for fibril formation. The model not only reproduces key
properties of fibril elongation measured in experiments, including
Aβ binding affinity, activation enthalpy of Aβ structural
transitions and a large time scale gap (τlock/τdock = 103–104) between Aβ
binding and its structural transitions, but also reveals detailed
pathways involving structural transitions not seen before, namely,
fibril formation both in hydrophobic regions L17-A21 and G37-A42 preceding
fibril formation in hydrophilic region E22-A30. Moreover, the model
identifies as important kinetic intermediates strand–loop–strand
(SLS) structures of Aβ monomers, long suspected to be related
to fibril elongation. The kinetic model suggests further that fibril
elongation arises faster at the fibril tip with exposed L17-A21, rather
than at the other tip, explaining thereby unidirectional fibril growth
observed previously in experiments.
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Affiliation(s)
- Wei Han
- Beckman Institute, ‡Center for Biophysics and Computational Biology, and §Department of Physics, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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18
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Ghoneim MM, Elokely KM, El-Hela AA, Mohammad AEI, Jacob M, Cutler SJ, Doerksen RJ, Ross SA. Isolation and characterization of new secondary metabolites from Asphodelus microcarpus. Med Chem Res 2014; 23:3510-3515. [PMID: 27713615 PMCID: PMC5048751 DOI: 10.1007/s00044-014-0928-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Phytochemical study of the ethanolic extract of Asphodelus microcarpus Salzm. et Viv. (Asphodelaceae) resulted in the isolation of two new compounds, methyl-1,4,5-trihydroxy-7-methyl-9,10-dioxo-9,10-dihydroanthracene-2-carboxylate (1), and (1R) 3,10-dimethoxy-5-methyl-1H-1,4-epoxybenzo[h]isochromene (2) as well as three known compounds; 3,4-dihydroxy-methyl benzoate (3), 3,4-dihydroxybenzoic acid (4), and 6-methoxychrysophanol (5). Compound 1 showed a potent activity against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus with IC50 values of 1.5 and 1.2 µg/mL, respectively. Compound 3 showed antileishmanial activity with an IC50 value of 33.2 µg/mL. Compound 2 is the first isochromene possessing a highly strained 1,4-epoxy moiety. The structure elucidation of isolated metabolites was carried out using spectroscopic data, the absolute configuration of 2 based on optical rotation and electronic circular dichroism experiments and calculations.
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Affiliation(s)
- Mohammed M. Ghoneim
- National Center for Natural Products Research, University of Mississippi, University, MS 38677, USA
- Department of Pharmacognosy, Faculty of Pharmacy, University of Al-Azhar, Cairo 11371, Egypt
| | - Khaled M. Elokely
- Department of Medicinal Chemistry and National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38677, USA
| | - Atef A. El-Hela
- Department of Pharmacognosy, Faculty of Pharmacy, University of Al-Azhar, Cairo 11371, Egypt
| | - Abd Elsalam I. Mohammad
- Department of Pharmacognosy, Faculty of Pharmacy, University of Al-Azhar, Cairo 11371, Egypt
| | - Melissa Jacob
- National Center for Natural Products Research, University of Mississippi, University, MS 38677, USA
| | - Stephen J. Cutler
- Department of Medicinal Chemistry and National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38677, USA
| | - Robert J. Doerksen
- Department of Medicinal Chemistry and National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38677, USA
| | - Samir A. Ross
- Department of Pharmacognosy and National Center for Natural Products Research, School of Pharmacy, University of Mississippi, University, MS 38677, USA
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19
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Levy RM, Dai W, Deng NJ, Makarov DE. How long does it take to equilibrate the unfolded state of a protein? Protein Sci 2013; 22:1459-65. [PMID: 23963761 DOI: 10.1002/pro.2335] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 08/09/2013] [Accepted: 08/12/2013] [Indexed: 01/18/2023]
Abstract
How long does it take to equilibrate the unfolded state of a protein? The answer to this question has important implications for our understanding of why many small proteins fold with two state kinetics. When the equilibration within the unfolded state U is much faster than the folding, the folding kinetics will be two state even if there are many folding pathways with different barriers. Yet the mean first passage times (MFPTs) between different regions of the unfolded state can be much longer than the folding time. This seems to imply that the equilibration within U is much slower than the folding. In this communication we resolve this paradox. We present a formula for estimating the time to equilibrate the unfolded state of a protein. We also present a formula for the MFPT to any state within U, which is proportional to the average lifetime of that state divided by the state population. This relation is valid when the equilibration within U is very fast as compared with folding as it often is for small proteins. To illustrate the concepts, we apply the formulas to estimate the time to equilibrate the unfolded state of Trp-cage and MFPTs within the unfolded state based on a Markov State Model using an ultra-long 208 microsecond trajectory of the miniprotein to parameterize the model. The time to equilibrate the unfolded state of Trp-cage is ∼100 ns while the typical MFPTs within U are tens of microseconds or longer.
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Affiliation(s)
- Ronald M Levy
- Department of Chemistry and Chemical Biology, Rutgers, the State University of New Jersey, Piscataway, New Jersey, 08854
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20
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Jimenez-Cruz CA, Garcia AE. Reconstructing the Most Probable Folding Transition Path from Replica Exchange Molecular Dynamics Simulations. J Chem Theory Comput 2013; 9:3750-5. [DOI: 10.1021/ct400170x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Camilo Andres Jimenez-Cruz
- Department of Physics,
Applied Physics and Astronomy,
and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180,
United States
| | - Angel E. Garcia
- Department of Physics,
Applied Physics and Astronomy,
and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180,
United States
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21
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Xia J, Deng NJ, Levy RM. NMR relaxation in proteins with fast internal motions and slow conformational exchange: model-free framework and Markov state simulations. J Phys Chem B 2013; 117:6625-34. [PMID: 23638941 DOI: 10.1021/jp400797y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Calculating NMR relaxation effects for proteins with dynamics on multiple time scales generally requires very long trajectories based on conventional molecular dynamics simulations. In this report, we have built Markov state models from multiple MD trajectories and used the resulting MSM to capture the very fast internal motions of the protein within a free energy basin on a time scale up to hundreds of picoseconds and the more than 3 orders of magnitude slower conformational exchange between macrostates. To interpret the relaxation data, we derive new equations using the model-free framework which includes two slowly exchanging macrostates, each of which also exhibits fast local motions. Using simulations of HIV-1 protease as an example, we show how the populations of slowly exchanging conformational states as well as order parameters for the different states can be determined from the NMR relaxation data.
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Affiliation(s)
- Junchao Xia
- Department of Chemistry and Chemical Biology and BioMaPS Institute for Quantitative Biology, Rutgers, the State University of New Jersey, 610 Taylor Road, Piscataway, New Jersey 08854, USA
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22
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Deng NJ, Zheng W, Gallicchio E, Levy RM. Insights into the dynamics of HIV-1 protease: a kinetic network model constructed from atomistic simulations. J Am Chem Soc 2011; 133:9387-94. [PMID: 21561098 DOI: 10.1021/ja2008032] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conformational dynamics in the flaps of HIV-1 protease plays a crucial role in the mechanism of substrate binding. We develop a kinetic network model, constructed from detailed atomistic simulations, to determine the kinetic mechanisms of the conformational transitions in HIV-1 PR. To overcome the time scale limitation of conventional molecular dynamics (MD) simulations, our method combines replica exchange MD with transition path theory (TPT) to study the diversity and temperature dependence of the pathways connecting functionally important states of the protease. At low temperatures the large-scale flap opening is dominated by a small number of paths; at elevated temperatures the transition occurs through many structurally heterogeneous routes. The expanded conformation in the crystal structure 1TW7 is found to closely mimic a key intermediate in the flap-opening pathways at low temperature. We investigated the different transition mechanisms between the semi-open and closed forms. The calculated relaxation times reveal fast semi-open ↔ closed transitions, and infrequently the flaps fully open. The ligand binding rate predicted from this kinetic model increases by 38-fold from 285 to 309 K, which is in general agreement with experiments. To our knowledge, this is the first application of a network model constructed from atomistic simulations together with TPT to analyze conformational changes between different functional states of a natively folded protein.
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Affiliation(s)
- Nan-jie Deng
- BioMaPS Institute for Quantitative Biology and Department of Chemistry and Chemical Biology, Rutgers, the State University of New Jersey, Piscataway, New Jersey 08854, USA
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23
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Cruz V, Ramos J, Martínez-Salazar J. Water-Mediated Conformations of the Alanine Dipeptide as Revealed by Distributed Umbrella Sampling Simulations, Quantum Mechanics Based Calculations, and Experimental Data. J Phys Chem B 2011; 115:4880-6. [DOI: 10.1021/jp2022727] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Víctor Cruz
- BIOPHYM, Instituto de Estructura de la Materia, CSIC, Serrano 113bis, 28006, Madrid, Spain
| | - Javier Ramos
- BIOPHYM, Instituto de Estructura de la Materia, CSIC, Serrano 113bis, 28006, Madrid, Spain
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24
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Campbell ZT, Baldwin TO, Miyashita O. Analysis of the bacterial luciferase mobile loop by replica-exchange molecular dynamics. Biophys J 2011; 99:4012-9. [PMID: 21156144 DOI: 10.1016/j.bpj.2010.11.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Revised: 10/21/2010] [Accepted: 11/01/2010] [Indexed: 12/29/2022] Open
Abstract
Bacterial luciferase contains an extended 29-residue mobile loop. Movements of this loop are governed by binding of either flavin mononucleotide (FMNH2) or polyvalent anions. To understand this process, loop dynamics were investigated using replica-exchange molecular dynamics that yielded conformational ensembles in either the presence or absence of FMNH2. The resulting data were analyzed using clustering and network analysis. We observed the closed conformations that are visited only in the simulations with the ligand. Yet the mobile loop is intrinsically flexible, and FMNH2 binding modifies the relative populations of conformations. This model provides unique information regarding the function of a crystallographically disordered segment of the loop near the binding site. Structures at or near the fringe of this network were compatible with flavin binding or release. Finally, we demonstrate that the crystallographically observed conformation of the mobile loop bound to oxidized flavin was influenced by crystal packing. Thus, our study has revealed what we believe are novel conformations of the mobile loop and additional context for experimentally determined structures.
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Affiliation(s)
- Zachary T Campbell
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona, USA
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25
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Mishra S, Meuwly M. Quantitative analysis of ligand migration from transition networks. Biophys J 2011; 99:3969-78. [PMID: 21156139 DOI: 10.1016/j.bpj.2010.09.068] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 09/22/2010] [Accepted: 09/29/2010] [Indexed: 11/24/2022] Open
Abstract
In this work we use transition network analysis for the first time to investigate ligand migration in truncated hemoglobin (trHbN) and obtain kinetic information about the docking-site dynamics in the protein. A comparison with explicit water molecular dynamics simulations (100 ns in total) shows that the rate constants derived from the network analysis are realistic. The transition network analysis provides 1) The time-resolved connectivity network in the protein; 2) The half-lives of the docking sites; 3) The transition timescales between two given docking sites; and 4) The extent of population transfer among different docking sites of the protein as a function of lag time. We investigate the role of the Tyr33 and Gln58 residues in ligand migration by studying ligand migration in four mutants of trHbN. The mutation study suggests that residues Tyr33 and Gln58 stabilize the NO ligand in the Xe2 docking site of trHbN, thus facilitating the efficiency of the NO detoxification reaction.
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26
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Zheng W, Gallicchio E, Deng N, Andrec M, Levy RM. Kinetic network study of the diversity and temperature dependence of Trp-Cage folding pathways: combining transition path theory with stochastic simulations. J Phys Chem B 2011; 115:1512-23. [PMID: 21254767 PMCID: PMC3059588 DOI: 10.1021/jp1089596] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present a new approach to study a multitude of folding pathways and different folding mechanisms for the 20-residue mini-protein Trp-Cage using the combined power of replica exchange molecular dynamics (REMD) simulations for conformational sampling, transition path theory (TPT) for constructing folding pathways, and stochastic simulations for sampling the pathways in a high dimensional structure space. REMD simulations of Trp-Cage with 16 replicas at temperatures between 270 and 566 K are carried out with an all-atom force field (OPLSAA) and an implicit solvent model (AGBNP). The conformations sampled from all temperatures are collected. They form a discretized state space that can be used to model the folding process. The equilibrium population for each state at a target temperature can be calculated using the weighted-histogram-analysis method (WHAM). By connecting states with similar structures and creating edges satisfying detailed balance conditions, we construct a kinetic network that preserves the equilibrium population distribution of the state space. After defining the folded and unfolded macrostates, committor probabilities (P(fold)) are calculated by solving a set of linear equations for each node in the network and pathways are extracted together with their fluxes using the TPT algorithm. By clustering the pathways into folding "tubes", a more physically meaningful picture of the diversity of folding routes emerges. Stochastic simulations are carried out on the network, and a procedure is developed to project sampled trajectories onto the folding tubes. The fluxes through the folding tubes calculated from the stochastic trajectories are in good agreement with the corresponding values obtained from the TPT analysis. The temperature dependence of the ensemble of Trp-Cage folding pathways is investigated. Above the folding temperature, a large number of diverse folding pathways with comparable fluxes flood the energy landscape. At low temperature, however, the folding transition is dominated by only a few localized pathways.
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Affiliation(s)
- Weihua Zheng
- Department of Chemistry and Chemical Biology and BioMaPS Institute for Quantitative Biology, Rutgers, the State University of New Jersey Piscataway, NJ 08854
| | - Emilio Gallicchio
- Department of Chemistry and Chemical Biology and BioMaPS Institute for Quantitative Biology, Rutgers, the State University of New Jersey Piscataway, NJ 08854
| | - Nanjie Deng
- Department of Chemistry and Chemical Biology and BioMaPS Institute for Quantitative Biology, Rutgers, the State University of New Jersey Piscataway, NJ 08854
| | - Michael Andrec
- Department of Chemistry and Chemical Biology and BioMaPS Institute for Quantitative Biology, Rutgers, the State University of New Jersey Piscataway, NJ 08854
| | - Ronald M. Levy
- Department of Chemistry and Chemical Biology and BioMaPS Institute for Quantitative Biology, Rutgers, the State University of New Jersey Piscataway, NJ 08854
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27
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Klenin K, Strodel B, Wales DJ, Wenzel W. Modelling proteins: conformational sampling and reconstruction of folding kinetics. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1814:977-1000. [PMID: 20851219 DOI: 10.1016/j.bbapap.2010.09.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 09/03/2010] [Accepted: 09/05/2010] [Indexed: 01/08/2023]
Abstract
In the last decades biomolecular simulation has made tremendous inroads to help elucidate biomolecular processes in-silico. Despite enormous advances in molecular dynamics techniques and the available computational power, many problems involve long time scales and large-scale molecular rearrangements that are still difficult to sample adequately. In this review we therefore summarise recent efforts to fundamentally improve this situation by decoupling the sampling of the energy landscape from the description of the kinetics of the process. Recent years have seen the emergence of many advanced sampling techniques, which permit efficient characterisation of the relevant family of molecular conformations by dispensing with the details of the short-term kinetics of the process. Because these methods generate thermodynamic information at best, they must be complemented by techniques to reconstruct the kinetics of the process using the ensemble of relevant conformations. Here we review recent advances for both types of methods and discuss their perspectives to permit efficient and accurate modelling of large-scale conformational changes in biomolecules. This article is part of a Special Issue entitled: Protein Dynamics: Experimental and Computational Approaches.
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Affiliation(s)
- Konstantin Klenin
- Steinbuch Centre for Computing, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany
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