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Manukyan AK. Structural aspects and activation mechanism of human secretory group IIA phospholipase. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2020; 49:511-531. [DOI: 10.1007/s00249-020-01458-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 08/12/2020] [Accepted: 08/14/2020] [Indexed: 11/30/2022]
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2
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Bouquiaux C, Tonnelé C, Castet F, Champagne B. Second-Order Nonlinear Optical Properties of an Amphiphilic Dye Embedded in a Lipid Bilayer. A Combined Molecular Dynamics–Quantum Chemistry Study. J Phys Chem B 2020; 124:2101-2109. [DOI: 10.1021/acs.jpcb.9b10988] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Charlotte Bouquiaux
- Theoretical Chemistry Laboratory, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, University of Namur, Rue de Bruxelles, 61, B-5000 Namur, Belgium
| | - Claire Tonnelé
- University of Bordeaux, Institut des Sciences Moléculaires, UMR 5255 CNRS, Cours de la Libération 351, F-33405 Talence Cedex, France
| | - Frédéric Castet
- University of Bordeaux, Institut des Sciences Moléculaires, UMR 5255 CNRS, Cours de la Libération 351, F-33405 Talence Cedex, France
| | - Benoît Champagne
- Theoretical Chemistry Laboratory, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter, University of Namur, Rue de Bruxelles, 61, B-5000 Namur, Belgium
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3
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Kasimova MA, Tewari D, Cowgill JB, Ursuleaz WC, Lin JL, Delemotte L, Chanda B. Helix breaking transition in the S4 of HCN channel is critical for hyperpolarization-dependent gating. eLife 2019; 8:e53400. [PMID: 31774399 PMCID: PMC6904216 DOI: 10.7554/elife.53400] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 11/19/2019] [Indexed: 12/19/2022] Open
Abstract
In contrast to most voltage-gated ion channels, hyperpolarization- and cAMP gated (HCN) ion channels open on hyperpolarization. Structure-function studies show that the voltage-sensor of HCN channels are unique but the mechanisms that determine gating polarity remain poorly understood. All-atom molecular dynamics simulations (~20 μs) of HCN1 channel under hyperpolarization reveals an initial downward movement of the S4 voltage-sensor but following the transfer of last gating charge, the S4 breaks into two sub-helices with the lower sub-helix becoming parallel to the membrane. Functional studies on bipolar channels show that the gating polarity strongly correlates with helical turn propensity of the substituents at the breakpoint. Remarkably, in a proto-HCN background, the replacement of breakpoint serine with a bulky hydrophobic amino acid is sufficient to completely flip the gating polarity from inward to outward-rectifying. Our studies reveal an unexpected mechanism of inward rectification involving a linker sub-helix emerging from HCN S4 during hyperpolarization.
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Affiliation(s)
- Marina A Kasimova
- Science for Life Laboratory, Department of Applied PhysicsKTH Royal Institute of TechnologyStockholmSweden
| | - Debanjan Tewari
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
| | - John B Cowgill
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
- Graduate program in BiophysicsUniversity of WisconsinMadisonUnited States
| | | | - Jenna L Lin
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
- Graduate program in BiophysicsUniversity of WisconsinMadisonUnited States
| | - Lucie Delemotte
- Science for Life Laboratory, Department of Applied PhysicsKTH Royal Institute of TechnologyStockholmSweden
| | - Baron Chanda
- Department of NeuroscienceUniversity of Wisconsin-MadisonMadisonUnited States
- Department of Biomolecular ChemistryUniversity of Wisconsin-MadisonMadisonUnited States
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4
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Pantelopulos GA, Nagai T, Bandara A, Panahi A, Straub JE. Critical size dependence of domain formation observed in coarse-grained simulations of bilayers composed of ternary lipid mixtures. J Chem Phys 2017; 147:095101. [PMID: 28886648 PMCID: PMC5648569 DOI: 10.1063/1.4999709] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/19/2017] [Indexed: 12/13/2022] Open
Abstract
Model cellular membranes are known to form micro- and macroscale lipid domains dependent on molecular composition. The formation of macroscopic lipid domains by lipid mixtures has been the subject of many simulation investigations. We present a critical study of system size impact on lipid domain phase separation into liquid-ordered and liquid-disordered macroscale domains in ternary lipid mixtures. In the popular di-C16:0 PC:di-C18:2 PC:cholesterol at 35:35:30 ratio mixture, we find systems with a minimum of 1480 lipids to be necessary for the formation of macroscopic phase separated domains and systems of 10 000 lipids to achieve structurally converged conformations similar to the thermodynamic limit. To understand these results and predict the behavior of any mixture forming two phases, we develop and investigate an analytical Flory-Huggins model which is recursively validated using simulation and experimental data. We find that micro- and macroscale domains can coexist in ternary mixtures. Additionally, we analyze the distributions of specific lipid-lipid interactions in each phase, characterizing domain structures proposed based on past experimental studies. These findings offer guidance in selecting appropriate system sizes for the study of phase separations and provide new insights into the nature of domain structure for a popular ternary lipid mixture.
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Affiliation(s)
- George A Pantelopulos
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - Tetsuro Nagai
- Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Aichi 464-8602, Japan
| | - Asanga Bandara
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - Afra Panahi
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
| | - John E Straub
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
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5
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Interactions stabilizing the C-terminal helix of human phospholipid scramblase 1 in lipid bilayers: A computational study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1200-1210. [DOI: 10.1016/j.bbamem.2017.03.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/09/2017] [Accepted: 03/29/2017] [Indexed: 12/19/2022]
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6
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Dutagaci B, Sayadi M, Feig M. Heterogeneous dielectric generalized Born model with a van der Waals term provides improved association energetics of membrane-embedded transmembrane helices. J Comput Chem 2017; 38:1308-1320. [PMID: 28160300 DOI: 10.1002/jcc.24691] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 10/18/2016] [Accepted: 11/17/2016] [Indexed: 11/07/2022]
Abstract
The heterogeneous dielectric generalized Born (HDGB) implicit membrane formalism is extended by the addition of a van der Waals dispersion term to better describe the nonpolar components of the free energy of solvation. The new model, termed HDGBvdW, improves the energy estimates in the hydrophobic interior of the membrane, where polar and charged species are rarely found and nonpolar interactions become significant. The implicit van der Waals term for the membrane environment extends the model from Gallicchio et al. (J. Comput. Chem. 2004, 25, 479) by combining separate contributions from each of the membrane components. The HDGBvdW model is validated with a series of test cases ranging from membrane insertion and pair association profiles of amino acid side chain analogs and transmembrane helices. Overall, the HDGBvdW model leads to increased agreement with explicit membrane simulation results and experimental data. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Bercem Dutagaci
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, 48824
| | - Maryam Sayadi
- Department of Chemistry, Michigan State University, East Lansing, Michigan, 48824
| | - Michael Feig
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, 48824
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7
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Lyubartsev AP, Rabinovich AL. Force Field Development for Lipid Membrane Simulations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2483-2497. [PMID: 26766518 DOI: 10.1016/j.bbamem.2015.12.033] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 12/21/2015] [Accepted: 12/23/2015] [Indexed: 02/04/2023]
Abstract
With the rapid development of computer power and wide availability of modelling software computer simulations of realistic models of lipid membranes, including their interactions with various molecular species, polypeptides and membrane proteins have become feasible for many research groups. The crucial issue of the reliability of such simulations is the quality of the force field, and many efforts, especially in the latest several years, have been devoted to parametrization and optimization of the force fields for biomembrane modelling. In this review, we give account of the recent development in this area, covering different classes of force fields, principles of the force field parametrization, comparison of the force fields, and their experimental validation. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
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Affiliation(s)
- Alexander P Lyubartsev
- Department of Materials and Environmental Chemistry, Stockholm University, SE 106 91, Stockholm, Sweden.
| | - Alexander L Rabinovich
- Institute of Biology, Karelian Research Center, Russian Academy of Sciences, Pushkinskaya 11, Petrozavodsk, 185910, Russian Federation.
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8
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Ulmschneider JP, Ulmschneider MB. Folding Simulations of the Transmembrane Helix of Virus Protein U in an Implicit Membrane Model. J Chem Theory Comput 2015; 3:2335-46. [PMID: 26636223 DOI: 10.1021/ct700103k] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vpu is an 81-amino-acid auxiliary membrane protein encoded by human immunodeficiency virus type 1 (HIV-1). One of its roles is to amplify viral release by self-assembling in homo-oligomers to form functional water-filled pores enabling the flux of ions across the membrane. Various NMR and CD studies have shown that the transmembrane domain of Vpu has a helical conformation. With a recently developed implicit membrane model and an efficient Monte Carlo (MC) algorithm using concerted backbone rotations, we simulate the folding of the transmembrane domain of Vpu at atomic resolution. The implicit membrane environment is based on the generalized Born theory and enables very long time scale events, such as folding to be observed using detailed all-atom representation of the protein. Such studies are currently computationally unfeasible with fully explicit lipid bilayer molecular dynamics simulations. The correct helical transmembrane structure of Vpu is predicted from extended conformations and remains stably inserted. Tilt and kink angles agree well with experimental estimates from NMR measurements. The experimentally observed change in tilt angle in membranes of varying hydrophobic width is accurately reproduced. The extensive simulation of a pentamer of the Vpu transmembrane domain in the implicit membrane gives results similar to the ones reported previously for fully explicit bilayer simulations.
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Affiliation(s)
- Jakob P Ulmschneider
- Department of Chemistry, University of Rome "La Sapienza", Rome, Italy, and Department of Biochemistry, University of Oxford, Oxford, U.K
| | - Martin B Ulmschneider
- Department of Chemistry, University of Rome "La Sapienza", Rome, Italy, and Department of Biochemistry, University of Oxford, Oxford, U.K
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9
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Moshfegh A, Ahmadi G, Jabbarzadeh A. Thermostatic and rheological responses of DPD fluid to extreme shear under modified Lees-Edwards boundary condition. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2015; 38:134. [PMID: 26701709 DOI: 10.1140/epje/i2015-15134-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2015] [Accepted: 11/20/2015] [Indexed: 06/05/2023]
Abstract
Thermodynamic, hydrodynamic and rheological interactions between velocity-dependent thermostats of Lowe-Andersen (LA) and Nosé-Hoover-Lowe-Andersen (NHLA), and modified Lees-Edwards (M-LEC) boundary condition were studied in the context of Dissipative Particle Dynamics method. Comparisons were made with original Lees-Edwards method to characterise the improvements that M-LEC offers in conserving the induced shear momentum. Different imposed shear velocities, heat bath collision/exchange frequencies and thermostating probabilities were considered. The presented analyses addressed an unusual discontinuity in momentum transfer that appeared in form of nonphysical jumps in velocity and temperature profiles. The usefulness of M-LEC was then quantified by evaluating the enhancements in obtained effective shear velocity, effective shear rate, Péclet number, and dynamic viscosity. System exchange frequency (Γ) with Maxwellian heat bath was found to play an important role, in that its larger values facilitated achieving higher shear rates with proper temperature control at the cost of deviation from an ideal momentum transfer. Similar dynamic viscosities were obtained under both shearing modes between LA and NHLA thermostats up to Γ = 10, whilst about twice the range of viscosity (1 < η < 20) was calculated for M-LEC at larger probabilities (ΓΔt > %). The main benefits of this modification were to facilitate momentum flow from shear boundaries to the system bulk. In addition, it was found that there exist upper thresholds for imposing shear on the system beyond which temperature cannot be controlled properly and nonphysical jumps reappear.
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Affiliation(s)
- Abouzar Moshfegh
- School of Aerospace, Mechanical and Mechatronic Eng., The University of Sydney, 2006, NSW, Australia.
| | - Goodarz Ahmadi
- Department of Mechanical and Aeronautical Engineering, Clarkson University, 13699-5725, Potsdam, NY, USA
| | - Ahmad Jabbarzadeh
- School of Aerospace, Mechanical and Mechatronic Eng., The University of Sydney, 2006, NSW, Australia
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Rajapaksha SP, Pal N, Zheng D, Lu HP. Protein-fluctuation-induced water-pore formation in ion channel voltage-sensor translocation across a lipid bilayer membrane. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:052719. [PMID: 26651735 DOI: 10.1103/physreve.92.052719] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Indexed: 06/05/2023]
Abstract
We have applied a combined fluorescence microscopy and single-ion-channel electric current recording approach, correlating with molecular dynamics (MD) simulations, to study the mechanism of voltage-sensor domain translocation across a lipid bilayer. We use the colicin Ia ion channel as a model system, and our experimental and simulation results show the following: (1) The open-close activity of an activated colicin Ia is not necessarily sensitive to the amplitude of the applied cross-membrane voltage when the cross-membrane voltage is around the resting potential of excitable membranes; and (2) there is a significant probability that the activation of colicin Ia occurs by forming a transient and fluctuating water pore of ∼15 Å diameter in the lipid bilayer membrane. The location of the water-pore formation is nonrandom and highly specific, right at the insertion site of colicin Ia charged residues in the lipid bilayer membrane, and the formation is intrinsically associated with the polypeptide conformational fluctuations and solvation dynamics. Our results suggest an interesting mechanistic pathway for voltage-sensitive ion channel activation, and specifically for translocation of charged polypeptide chains across the lipid membrane under a transmembrane electric field: the charged polypeptide domain facilitates the formation of hydrophilic water pore in the membrane and diffuses through the hydrophilic pathway across the membrane; i.e., the charged polypeptide chain can cross a lipid membrane without entering into the hydrophobic core of the lipid membrane but entirely through the aqueous and hydrophilic environment to achieve a cross-membrane translocation. This mechanism sheds light on the intensive and fundamental debate on how a hydrophilic and charged peptide domain diffuses across the biologically inaccessible high-energy barrier of the hydrophobic core of a lipid bilayer: The peptide domain does not need to cross the hydrophobic core to move across a lipid bilayer.
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Affiliation(s)
- Suneth P Rajapaksha
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
| | - Nibedita Pal
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
| | - Desheng Zheng
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
| | - H Peter Lu
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
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11
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Ramakrishna S, Padhi S, Priyakumar UD. Modeling the structure of SARS 3a transmembrane protein using a minimum unfavorable contact approach. J CHEM SCI 2015; 127:2159-2169. [PMID: 32218650 PMCID: PMC7090505 DOI: 10.1007/s12039-015-0982-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 09/02/2015] [Accepted: 09/04/2015] [Indexed: 12/11/2022]
Abstract
3a is an accessory protein from SARS coronavirus that is known to play a significant role in the proliferation of the virus by forming tetrameric ion channels. Although the monomeric units are known to consist of three transmembrane (TM) domains, there are no solved structures available for the complete monomer. The present study proposes a structural model for the transmembrane region of the monomer by employing our previously tested approach, which predicts potential orientations of TM α-helices by minimizing the unfavorable contact surfaces between the different TM domains. The best model structure comprising all three α-helices has been subjected to MD simulations to examine its quality. The TM bundle was found to form a compact and stable structure with significant intermolecular interactions. The structural features of the proposed model of 3a account for observations from previous experimental investigations on the activity of the protein. Further analysis indicates that residues from the TM2 and TM3 domains are likely to line the pore of the ion channel, which is in good agreement with a recent experimental study. In the absence of an experimental structure for the protein, the proposed structure can serve as a useful model for inferring structure-function relationships about the protein. The structure of the membrane protein 3a from SARS coronavirus is modeled using an approach that minimizes unfavorable contacts between transmembrane domains. A structure for a complete monomeric form of the protein thereby proposed is able to account for the behavior of the protein reported in previous experimental studies. ![]()
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Affiliation(s)
- S Ramakrishna
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, 500 032 India
| | - Siladitya Padhi
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, 500 032 India
| | - U Deva Priyakumar
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, 500 032 India
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12
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Steinhauser MO, Schmidt M. Destruction of cancer cells by laser-induced shock waves: recent developments in experimental treatments and multiscale computer simulations. SOFT MATTER 2014; 10:4778-88. [PMID: 24818846 DOI: 10.1039/c4sm00407h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
In this emerging area article we review recent progress in the mechanical destruction of cancer cells using laser-induced shock waves. The pure mechanical damaging and destruction of cancer cells associated with this technique possibly opens up a new route to tumor treatments and the corresponding therapies. At the same time progress in multiscale simulation techniques makes it possible to simulate mechanical properties of soft biological matter such as membranes, cytoskeletal networks and even whole cells and tissue. In this way an interdisciplinary approach to understanding key mechanisms in shock wave interactions with biological matter has become accessible. Mechanical properties of biological materials are also critical for many physiological processes and cover length scales ranging from the atomistic to the macroscopic scale. We argue that the latest developments and progress in experimentation enable the investigation of the shock wave interaction with cancer cells on multiple time- and length-scales. In this way the integrated use of experiment and simulation can address key challenges in this field. The exploration of the biological effects of laser-generated shock waves on a fundamental level constitutes an emerging multidisciplinary research area combining scientific methods from the areas of physics, biology, medicine and computer science.
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Affiliation(s)
- Martin Oliver Steinhauser
- Fraunhofer Research Group "Shock Waves in Soft Biological Matter", Ernst-Mach-Institut, EMI, Eckerstrasse 4, Freiburg, Germany.
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13
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Rabinovich AL, Lyubartsev AP. Computer simulation of lipid membranes: Methodology and achievements. POLYMER SCIENCE SERIES C 2013. [DOI: 10.1134/s1811238213070060] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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14
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Panahi A, Feig M. Dynamic Heterogeneous Dielectric Generalized Born (DHDGB): An implicit membrane model with a dynamically varying bilayer thickness. J Chem Theory Comput 2013; 9:1709-1719. [PMID: 23585740 PMCID: PMC3622271 DOI: 10.1021/ct300975k] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
An extension to the heterogeneous dielectric generalized Born (HDGB) implicit membrane formalism is presented to allow dynamic membrane deformations in response to membrane-inserted biomolecules during molecular dynamic simulations. The flexible membrane is implemented through additional degrees of freedom that represent the membrane deformation at the contact points of a membrane-inserted solute with the membrane. The extra degrees of freedom determine the dielectric and non-polar solvation free energy profiles that are used to obtain the solvation free energy in the presence of the membrane and are used to calculate membrane deformation free energies according to an elastic membrane model. With the dynamic HDGB (DHDGB) model the membrane is able to deform in response to the insertion of charged molecules thereby avoiding the overestimation of insertion free energies with static membrane models. The DHDGB model also allows the membrane to respond to the insertion of membrane-spanning solutes with hydrophobic mismatch. The model is tested with the membrane insertion of amino acid side chain analogs, arginine-containing helices, the WALP23 peptide, and the gramicidin A channel.
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Affiliation(s)
- Afra Panahi
- Department of Chemistry, Michigan State University, East Lansing, MI, 48824
| | - Michael Feig
- Department of Chemistry, Michigan State University, East Lansing, MI, 48824
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, 48824
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15
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Molecular Dynamics Simulations of Lipid Membrane Electroporation. J Membr Biol 2012; 245:531-43. [DOI: 10.1007/s00232-012-9434-6] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 04/30/2012] [Indexed: 10/28/2022]
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Monajjemi M, Farahani N, Mollaamin F. Thermodynamic study of solvent effects on nanostructures: phosphatidylserine and phosphatidylinositol membranes. PHYSICS AND CHEMISTRY OF LIQUIDS 2012. [DOI: 10.1080/00319104.2010.527842] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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17
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Polyansky AA, Volynsky PE, Efremov RG. Structural, dynamic, and functional aspects of helix association in membranes: a computational view. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2012; 83:129-61. [PMID: 21570667 DOI: 10.1016/b978-0-12-381262-9.00004-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This review surveys recent achievements of molecular computer modeling in understanding spatial structure, dynamics, and mechanisms of functioning of transmembrane α-helical dimers in membranes. The factors driving self-association of hydrophobic helices in the membrane milieu are considered with examples of their applications to biologically relevant problems. The emphasis is made on the recent results, which help to understand important aspects of structure-function relations for these systems and their biological activity. Limitations and shortcomings of the methods, along with their perspectives in design of new membrane active agents, are discussed.
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Affiliation(s)
- Anton A Polyansky
- M. M. Shemyakin and Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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18
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Liu A, Qi X. Molecular Dynamics Simulations of DOPC Lipid Bilayers: The Effect of Lennard-Jones Parameters of Hydrocarbon Chains. ACTA ACUST UNITED AC 2012; 2:78-82. [PMID: 26146594 DOI: 10.4236/cmb.2012.23007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The current Chemistry at Harvard Molecular Mechanics (CHARMM) force field cannot accurately describe the properties of unsaturated phospholipid membranes. In this paper, a series of simulations was performed in which the Lennard-Jones (L-J) parameters of lipid acyl chains of dioleoylphosphatidylcholine (DOPC) were systematically adjusted. The results showed that adjustment of the L-J parameters in lipid acyl chains can significantly improve the current CHARMM force field. It was found that the L-J parameters have different influences on the order parameters of the top half and bottom half of the chain, separated by the cis double bond. The order parameters of the top half and the bottom half of the chain are related to the area/lipid and the length of the chain, respectively.
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Affiliation(s)
- Anping Liu
- Leadership Computing Facility, Argonne National Laboratory, Argonne, USA
| | - Xiaoyang Qi
- Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, USA ; Division of Human Genetics, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, USA
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Xu W, Wei G, Su H, Nordenskiöld L, Mu Y. Effects of cholesterol on pore formation in lipid bilayers induced by human islet amyloid polypeptide fragments: a coarse-grained molecular dynamics study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:051922. [PMID: 22181459 DOI: 10.1103/physreve.84.051922] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Indexed: 05/31/2023]
Abstract
Disruption of the cellular membrane by the amyloidogenic peptide, islet amyloid polypeptide (IAPP), has been considered as one of the mechanisms of β-cell death during type 2 diabetes. The N-terminal region (residues 1-19) of the human version of IAPP is suggested to be primarily responsible for the membrane-disrupting effect of the full-length hIAPP peptide. However, the detailed assembly mode of hIAPP1-19 with membrane remains unclear. To gain insight into the interactions of hIAPP1-19 oligomer with the model membrane, we have employed coarse-grained molecular dynamics self-assembly simulations to study the aggregation of hIAPP1-19 fragments in the binary lipid made of zwitterionic dipalmitoylphosphatidylcholine (DPPC) and anionic dipalmitoylphosphatidylserine (DPPS) in the presence and absence of different levels of cholesterol content. The membrane-destabilizing effect of hIAPP1-19 is found to be modulated by the presence of cholesterol. In the absence of cholesterol, hIAPP1-19 aggregates prefer to locate inside the bilayer, forming pore-like assemblies. While in the presence of cholesterol molecules, the lipid bilayer becomes more ordered and stiff, and the hIAPP1-19 aggregates are dominantly positioned at the bilayer-water interface. The action of cholesterol may suggest a possible way to maintain the membrane integrity by small molecule interference.
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Affiliation(s)
- Weixin Xu
- State Key Laboratory of Precision Spectroscopy, Institutes for Advanced Interdisciplinary Research, East China Normal University, Shanghai, China
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20
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Frank A, Andricioaei I. A comparative study on the ability of two implicit solvent lipid models to predict transmembrane helix tilt angles. J Membr Biol 2010; 239:57-62. [PMID: 21152910 PMCID: PMC3030950 DOI: 10.1007/s00232-010-9325-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2010] [Accepted: 11/05/2010] [Indexed: 11/30/2022]
Abstract
Free-energy profiles describing the relative orientation of membrane proteins along predefined coordinates can be efficiently calculated by means of umbrella simulations. Such simulations generate reliable orientational distributions but are difficult to converge because of the very long equilibration times of the solvent and the lipid bilayer in explicit representation. Two implicit lipid membrane models are here applied in combination with the umbrella sampling strategy to the simulation of the transmembrane (TM) helical segment from virus protein U (Vpu). The models are used to study both orientation and energetics of this α-helical peptide as a function of hydrophobic mismatch. We observe that increasing the degree of positive hydrophobic mismatch increased the tilt angle of Vpu. These findings agree well with experimental data and as such validate the solvation models used in this study.
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Affiliation(s)
- Aaron Frank
- Department of Chemistry, University of California, Irvine, CA 92697, USA
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21
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Broemstrup T, Reuter N. Molecular dynamics simulations of mixed acidic/zwitterionic phospholipid bilayers. Biophys J 2010; 99:825-33. [PMID: 20682260 DOI: 10.1016/j.bpj.2010.04.064] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 04/21/2010] [Accepted: 04/23/2010] [Indexed: 10/19/2022] Open
Abstract
Anionic lipids are key components in the cell membranes. Many cell-regulatory and signaling mechanisms depend upon a complicated interplay between them and membrane-bound proteins. Phospholipid bilayers are commonly used as model systems in experimental or theoretical studies to gain insight into the structure and dynamics of biological membranes. We report here 200-ns-long MD simulations of pure (DMPC and DMPG) and mixed equimolar (DMPC/DMPG, DMPC/DMPS, and DMPC/DMPA) bilayers that each contain 256 lipids. The intra- and intermolecular interaction patterns in pure and mixed bilayers are analyzed and compared. The effect of monovalent ions (Na+) on the formation of salt-bridges is investigated. In particular, the number of Na(+)-mediated clusters in the presence of DMPS is higher than with DMPG and DMPA. We observe a preferential clustering of DMPS (and to some extent DMPA) lipids together rather than with DMPC molecules, which can explain the phase separation observed experimentally for DMPC/DMPS and DMPC/DMPA bilayers.
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Affiliation(s)
- Torben Broemstrup
- Computational Biology Unit, Bergen Center for Computational Science, University of Bergen, Bergen, Norway
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22
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Gofman Y, Linser S, Rzeszutek A, Shental-Bechor D, Funari SS, Ben-Tal N, Willumeit R. Interaction of an antimicrobial peptide with membranes: experiments and simulations with NKCS. J Phys Chem B 2010; 114:4230-7. [PMID: 20201501 DOI: 10.1021/jp909154y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We used Monte Carlo simulations and biophysical measurements to study the interaction of NKCS, a derivative of the antimicrobial peptide NK-2, with a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) membrane. The simulations showed that NKCS adsorbed on the membrane surface and the dominant conformation featured two amphipathic helices connected by a hinge region. We designed two mutants in the hinge to investigate the interplay between helicity and membrane affinity. Simulations with a Leu-to-Pro substitution showed that the helicity and membrane affinity of the mutant (NKCS-[LP]) decreased. Two Ala residues were added to NKCS to produce a sequence that is compatible with a continuous amphipathic helix structure (NKCS-[AA]), and the simulations showed that the mutant adsorbed on the membrane surface with a particularly high affinity. The circular dichroism spectra of the three peptides also showed that NKCS-[LP] is the least helical and NKCS-[AA] is the most. However, the activity of the peptides, determined in terms of their antimicrobial potency and influence on the temperature of the transition of the lipid to hexagonal phase, displayed a complex behavior: NKCS-[LP] was the least potent and had the smallest influence on the transition temperature, and NKCS was the most potent and had the largest effect on the temperature.
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Affiliation(s)
- Yana Gofman
- GKSS Research Center, 21502 Geesthacht, Germany
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23
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De Vita R, Stewart IW. Nonlinearities in tilt and layer displacements of planar lipid bilayers. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2010; 32:319-326. [PMID: 20614152 DOI: 10.1140/epje/i2010-10615-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2009] [Revised: 02/24/2010] [Accepted: 06/09/2010] [Indexed: 05/29/2023]
Abstract
A novel continuum model is proposed to describe the deformations of a planar lipid bilayer suspended across a circular pore. The model is derived within a new theoretical framework for smectic A liquid crystals in which the usual director n, which defines the average orientation of the molecules, is not constrained to be normal to the layers. The free energy is defined by considering the elastic splay of the director, the bending and compression of the lipid bilayer, the cost of tilting the director with respect to the layer normal, the surface tension, and the weak anchoring of the director. Variational methods are used to derive the equilibrium equations and boundary conditions. The resulting boundary value problem is then solved numerically to compute the fully nonlinear displacement of the layers and tilt of the lipid molecules. A parametric study shows that an increase in surface tension produces a decrease in the deformation of the lipid bilayers while an opposite effect is obtained when increasing the anchoring strength.
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Affiliation(s)
- R De Vita
- Engineering Science and Mechanics Department, Virginia Tech, Blacksburg, VA, USA.
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24
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Stary A, Wacker SJ, Boukharta L, Zachariae U, Karimi-Nejad Y, Aqvist J, Vriend G, de Groot BL. Toward a consensus model of the HERG potassium channel. ChemMedChem 2010; 5:455-67. [PMID: 20104563 DOI: 10.1002/cmdc.200900461] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Malfunction of hERG potassium channels, due to inherited mutations or inhibition by drugs, can cause long QT syndrome, which can lead to life-threatening arrhythmias. A three-dimensional structure of hERG is a prerequisite to understand the molecular basis of hERG malfunction. To achieve a consensus model, we carried out an extensive analysis of hERG models based on various alignments of helix S5. We analyzed seven models using a combination of conventional geometry/packing/normality validation methods as well as molecular dynamics simulations and molecular docking. A synthetic test set with the X-ray crystal structure of K(v)1.2 with artificially shifted S5 sequences modeled into the structure served as a reference case. We docked the known hERG inhibitors (+)-cisapride, (S)-terfenadine, and MK-499 into the hERG models and simulation snapshots. None of the single analyses unambiguously identified a preferred model, but the combination of all three revealed that there is only one model that fulfils all quality criteria. This model is confirmed by a recent mutation scanning experiment (P. Ju, G. Pages, R. P. Riek, P. C. Chen, A. M. Torres, P. S. Bansal, S. Kuyucak, P. W. Kuchel, J. I. Vandenberg, J. Biol. Chem. 2009, 284, 1000-1008). We expect the modeled structure to be useful as a basis both for computational studies of channel function and kinetics as well as the design of experiments.
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Affiliation(s)
- Anna Stary
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
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25
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Bocharov EV, Volynsky PE, Pavlov KV, Efremov RG, Arseniev AS. Structure elucidation of dimeric transmembrane domains of bitopic proteins. Cell Adh Migr 2010; 4:284-98. [PMID: 20421711 DOI: 10.4161/cam.4.2.11930] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The interaction between transmembrane helices is of great interest because it directly determines biological activity of a membrane protein. Either destroying or enhancing such interactions can result in many diseases related to dysfunction of different tissues in human body. One much studied form of membrane proteins known as bitopic protein is a dimer containing two membrane-spanning helices associating laterally. Establishing structure-function relationship as well as rational design of new types of drugs targeting membrane proteins requires precise structural information about this class of objects. At present time, to investigate spatial structure and internal dynamics of such transmembrane helical dimers, several strategies were developed based mainly on a combination of NMR spectroscopy, optical spectroscopy, protein engineering and molecular modeling. These approaches were successfully applied to homo- and heterodimeric transmembrane fragments of several bitopic proteins, which play important roles in normal and in pathological conditions of human organism.
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Affiliation(s)
- Eduard V Bocharov
- Division of Structural Biology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russia.
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26
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Morisada S, Shinto H. Implicit Solvent Model Simulations of Surfactant Self-Assembly in Aqueous Solutions. J Phys Chem B 2010; 114:6337-43. [DOI: 10.1021/jp100887g] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shintaro Morisada
- Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8502, Japan, and Department of Chemical Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Hiroyuki Shinto
- Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8502, Japan, and Department of Chemical Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
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27
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Abroshan H, Akbarzadeh H, Parsafar GA. Molecular dynamics simulation and MM-PBSA calculations of sickle cell hemoglobin in dimer form with Val, Trp, or Phe at the lateral contact. J PHYS ORG CHEM 2010. [DOI: 10.1002/poc.1679] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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28
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Almeida JAS, Marques EF, Jurado AS, Pais AACC. The effect of cationic gemini surfactants upon lipid membranes. An experimental and molecular dynamics simulation study. Phys Chem Chem Phys 2010; 12:14462-76. [DOI: 10.1039/c0cp00950d] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Abstract
The outer membrane of Gram-negative bacteria serves as a protective barrier against the external environment but is rendered selectively permeable to nutrients and waste by proteins called porins. Other outer membrane proteins (OMPs) provide the membrane with a variety of other functions including active transport, catalysis, pathogenesis and signal transduction. A relatively small number of crystal or NMR structures of these proteins are known, and it is therefore essential that the maximum possible information be extracted. In this respect, computational techniques enable extrapolation from time- and space-averaged static structures to dynamic, physiological events. Electrostatics approaches have been used to investigate the structures of porins. The stochastic simulation of ion trajectories through these channels has been possible with Brownian dynamics, which treats the membrane and solvent approximately, enabling the prediction of conduction properties. Molecular dynamics has also been applied, enabling fully atomistic descriptions of 'virtual outer membranes'. This has provided atomic resolution descriptions of solute permeation through porins. It has also yielded insights into the dynamics of gating in active transporters and ion channels, as well as providing clues to catalytic mechanisms in outer membrane enzymes. Additionally, simulations are beginning to reveal the common features of interactions between membrane proteins and lipids, with biological implications for OMP folding, stability and mechanism. Future prospects include the simulation of longer, larger and more complex outer membrane systems, with more accurate descriptions of inter-atomic forces.
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Affiliation(s)
- Peter J Bond
- Department of Biochemistry, The University of Oxford, Oxford, UK
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30
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Ulmschneider MB, Ulmschneider JP. Membrane adsorption, folding, insertion and translocation of synthetic trans-membrane peptides. Mol Membr Biol 2009; 25:245-57. [DOI: 10.1080/09687680802020313] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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31
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Ulmschneider JP, Ulmschneider MB. Sampling efficiency in explicit and implicit membrane environments studied by peptide folding simulations. Proteins 2008; 75:586-97. [DOI: 10.1002/prot.22270] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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32
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Abstract
Maculatin 1.1 (M1.1) is a membrane-active antimicrobial peptide (AMP) from an Australian tree frog that forms a kinked amphipathic alpha-helix in the presence of a lipid bilayer or bilayer-mimetic environment. To help elucidate its mechanism of membrane-lytic activity, we performed a total of approximately 8 micros of coarse-grained molecular dynamics (CG-MD) simulations of M1.1 in the presence of zwitterionic phospholipid membranes. Several systems were simulated in which the peptide/lipid ratio was varied. At a low peptide/lipid ratio, M1.1 adopted a kinked, membrane-interfacial location, consistent with experiment. At higher peptide/lipid ratios, we observed spontaneous, cooperative membrane insertion of M1.1 peptide aggregates. The minimum size for formation of a transmembrane (TM) aggregate was just four peptides. The absence of a simple and well-defined central channel, along with the exclusion of lipid headgroups from the aggregates, suggests that a pore-like model is an unlikely explanation for the mechanism of membrane lysis by M1.1. We also performed an extended 1.25 micros simulation of the permeabilization of a complete liposome by multiple peptides. Consistent with the simpler bilayer simulations, formation of monomeric interfacial peptides and TM peptide clusters was observed. In contrast, major structural changes were observed in the vesicle membrane, implicating induced membrane curvature in the mechanism of active antimicrobial peptide lysis. This contrasted with the behavior of the nonpore-forming model peptide WALP23, which inserted into the vesicle to form extended clusters of TM alpha-helices with relatively little perturbation of bilayer properties.
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33
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Pereira CS, Hünenberger PH. The influence of polyhydroxylated compounds on a hydrated phospholipid bilayer: a molecular dynamics study. MOLECULAR SIMULATION 2008. [DOI: 10.1080/08927020701784762] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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34
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Preface. CURRENT TOPICS IN MEMBRANES 2008. [DOI: 10.1016/s1063-5823(08)00017-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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35
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Sapay N, Tieleman DP. Chapter 4 Molecular Dynamics Simulation of Lipid–Protein Interactions. CURRENT TOPICS IN MEMBRANES 2008. [DOI: 10.1016/s1063-5823(08)00004-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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36
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Cheng MH, Liu LT, Saladino AC, Xu Y, Tang P. Molecular dynamics simulations of ternary membrane mixture: phosphatidylcholine, phosphatidic acid, and cholesterol. J Phys Chem B 2007; 111:14186-92. [PMID: 18052271 DOI: 10.1021/jp075467b] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A ternary mixture of 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC), 1-palmitoyl-2-oleoyl phosphatidic acid (POPA), and cholesterol (CHOL) works effectively for a functional conformation of nicotinic acetylcholine receptor (nAChR) that can undergo agonist-induced conformation changes, but POPC alone can stabilize only a desensitized state of nAChR. To gain insights into the lipid mixture that has strong impact to nAChR functions, we performed more than 50 ns all atom molecular dynamic (MD) simulations at 303 K on a fully hydrated bilayer consisting of 240 POPC, 80 POPA, and 80 CHOL (3:1:1). The MD simulation revealed various interactions between different types of molecular pairs that ultimately regulated lipid organization. The heterogeneous interactions among three different constituents resulted in a broad spectrum of lipid properties, including extensive distributions of average area per lipid and varied lipid ordering as a function of lipid closeness to CHOL. Higher percentage of POPA than POPC had close association with CHOL, which coincided with relatively higher ordering of POPA molecules in their acyl chains near lipid head groups. Lower fraction of gauche dihedrals was also found in the same region of POPA. Although the CHOL molecules had the effects on the enhancement of surrounding lipid order, relatively low lipid order parameters and high fraction of gauche bonds were observed in the ternary mixture. Collectively, these results suggest that the dynamical structure of the ternary system could be determinant for a functional nAChR.
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Affiliation(s)
- Mary Hongying Cheng
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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37
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Polyansky AA, Volynsky PE, Nolde DE, Arseniev AS, Efremov RG. Role of lipid charge in organization of water/lipid bilayer interface: insights via computer simulations. J Phys Chem B 2007; 109:15052-9. [PMID: 16852905 DOI: 10.1021/jp0510185] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Anionic unsaturated lipid bilayers represent suitable model systems that mimic real cell membranes: they are fluid and possess a negative surface charge. Understanding of detailed molecular organization of water-lipid interfaces in such systems may provide an important insight into the mechanisms of proteins' binding to membranes. Molecular dynamics (MD) of full-atom hydrated lipid bilayers is one of the most powerful tools to address this problem in silico. Unfortunately, wide application of computational methods for such systems is limited by serious technical problems. They are mainly related to correct treatment of long-range electrostatic effects. In this study a physically reliable model of an anionic unsaturated bilayer of 1,2-dioleoyl-sn-glycero-3-phosphoserine (DOPS) was elaborated and subjected to long-term MD simulations. Electrostatic interactions were treated with two different algorithms: spherical cutoff function and particle-mesh Ewald summation (PME). To understand the role of lipid charge in the system behavior, similar calculations were also carried out for zwitterionic bilayer composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). It was shown that, for the charged DOPS bilayer, the PME protocol performs much better than the cutoff scheme. In the last case a number of artifacts in the structural organization of the bilayer were observed. All of them were attributed to inadequate treatment of electrostatic interactions of lipid headgroups with counterions. Electrostatic properties, along with structural and dynamic parameters, of both lipid bilayers were investigated. Comparative analysis of the MD data reveals that the water-lipid interface of the DOPC bilayer is looser than that for DOPS. This makes possible deeper penetration of water molecules inside the zwitterionic (DOPC) bilayer, where they strongly interact with carbonyls of lipids. This can lead to thickening of the membrane interface in zwitterionic as compared to negatively charged bilayers.
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Affiliation(s)
- Anton A Polyansky
- Department of Bioengineering, Biological Faculty, M. V. Lomonosov Moscow State University, Moscow 119992, Russia.
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38
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Ulmschneider JP, Ulmschneider MB, Di Nola A. Monte carlo folding of trans-membrane helical peptides in an implicit generalized Born membrane. Proteins 2007; 69:297-308. [PMID: 17600830 DOI: 10.1002/prot.21519] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
An efficient Monte Carlo (MC) algorithm using concerted backbone rotations is combined with a recently developed implicit membrane model to simulate the folding of the hydrophobic transmembrane domain M2TM of the M2 protein from influenza A virus and Sarcolipin at atomic resolution. The implicit membrane environment is based on generalized Born theory and has been calibrated against experimental data. The MC sampling has previously been used to fold several small polypeptides and been shown to be equivalent to molecular dynamics (MD). In combination with a replica exchange algorithm, M2TM is found to form continuous membrane spanning helical conformations for low temperature replicas. Sarcolipin is only partially helical, in agreement with the experimental NMR structures in lipid bilayers and detergent micelles. Higher temperature replicas exhibit a rapidly decreasing helicity, in agreement with expected thermodynamic behavior. To exclude the possibility of an erroneous helical bias in the simulations, the model is tested by sampling a synthetic Alanine-rich polypeptide of known helicity. The results demonstrate there is no overstabilization of helical conformations, indicating that the implicit model captures the essential components of the native membrane environment for M2TM and Sarcolipin.
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39
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Berkowitz ML, Bostick DL, Pandit S. Aqueous solutions next to phospholipid membrane surfaces: insights from simulations. Chem Rev 2007; 106:1527-39. [PMID: 16608190 DOI: 10.1021/cr0403638] [Citation(s) in RCA: 220] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Max L Berkowitz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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40
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Nishizawa M, Nishizawa K. Molecular dynamics simulations of a stretch-activated channel inhibitor GsMTx4 with lipid membranes: two binding modes and effects of lipid structure. Biophys J 2007; 92:4233-43. [PMID: 17384064 PMCID: PMC1877766 DOI: 10.1529/biophysj.106.101071] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Accepted: 02/12/2007] [Indexed: 11/18/2022] Open
Abstract
Our recent molecular dynamics simulation study of hanatoxin 1 (HaTx1), a gating modifier that binds to the voltage sensor of K(+) channels, has shown that HaTx1 has the ability to interact with carbonyl oxygen atoms of both leaflets of the lipid bilayer membrane and to be located at a deep position within the membrane. Here we performed a similar study of GsMTx4, a stretch-activated channels inhibitor, belonging to the same peptide family as HaTx1. Both toxins have an ellipsoidal shape, a belt of positively charged residues around the periphery, and a hydrophobic protrusion. Results show that, like HaTx1, GsMTx4 can interact with the membrane in two different ways. When all the positively charged residues interact with the outer leaflet lipid, GsMTx4 can assume a shallow binding mode. On the other hand, when the electrostatic interaction brings the positively charged groups of K-8 and K-28 into the vicinity of the carbonyl oxygen atoms of the inner leaflet lipids, the system exhibits a deep binding mode. This deep mode is accompanied by local membrane thinning. For both HaTx1 and GsMTx4, our mean force measurement analyses show that the deep binding mode is energetically favored over the shallow mode when a DPPC (dipalmitoyl-phosphatidylcholine) membrane is used at 310 K. In contrast, when a POPC (palmitooleoyl-phosphatidylcholine) membrane is used at 310 K, the two binding modes exhibited similar stability for both toxins. Similar analyses with DPPC membrane at 330 K led to an intermediary result between the above two results. Therefore, the structure of the lipid acyl chains appears to influence the location and the dynamics of the toxins within biological membranes. We also compared the behavior of an arginine and a lysine residue within the membrane. This is of interest because the arginine residue interaction with the lipid carbonyl oxygen atoms mediates the deep binding mode for HaTx1, whereas the lysine residue plays that role for GsMTx4. The arginine residue generally shows smoother dynamics near the lipid carbonyl oxygen atoms than the lysine residue. This difference between arginine and lysine may partly account for the functional diversity of the members of the toxin family.
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Affiliation(s)
- Manami Nishizawa
- Department of Biochemistry, Teikyo University School of Medicine, Kaga, Itabashi, Tokyo 173-8605, Japan
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41
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Sýkora J, Slavícek P, Jungwirth P, Barucha J, Hof M. Time-dependent stokes shifts of fluorescent dyes in the hydrophobic backbone region of a phospholipid bilayer: combination of fluorescence spectroscopy and ab initio calculations. J Phys Chem B 2007; 111:5869-77. [PMID: 17488002 DOI: 10.1021/jp0719255] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We explored the time-dependent Stokes shifts of fluorescent dyes containing an anthroyloxy chromophore (2-AS, 9-AS, and 16-AP) in bilayers composed of palmitoyl-oleoyl-phosphatidylcholine. The obtained data revealed a nontrivial solvation response of these dyes, which are located in the backbone region of the bilayer with a gradually increasing depth. For comparison, steady-state emission spectra in the neat solvents of various polarities and viscosities were also recorded. The results indicate that on the short picosecond time scale the AS dyes undergo complex photophysics including formation of states with a charge-transfer character. This observation is supported by ab initio calculations of the excited states of 9-methylanthroate. The slower nanosecond part of the relaxation process can be attributed to the solvation response of the dyes. A slowdown in solvent relaxation is observed upon moving toward the center of the bilayer. A mechanism similar to preferential solvation present in the mixture of a polar and nonpolar solvent is considered to explain the obtained data.
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Affiliation(s)
- Jan Sýkora
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 3, Prague 8, Czech Republic.
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42
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Heine DR, Rammohan AR, Balakrishnan J. Atomistic simulations of the interaction between lipid bilayers and substrates. MOLECULAR SIMULATION 2007. [DOI: 10.1080/08927020601154124] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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43
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Morisada S, Shinto H, Higashitani K. Revised Implicit Solvent Model for the Simulation of Surfactants in Aqueous Solutions. 2. Modeling of Charged Headgroups at Oil−Water Interface. J Chem Theory Comput 2007; 3:1163-71. [DOI: 10.1021/ct600311t] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shintaro Morisada
- Department of Chemical Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Hiroyuki Shinto
- Department of Chemical Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Ko Higashitani
- Department of Chemical Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
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44
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Chang R, Ayton GS, Voth GA. Multiscale coupling of mesoscopic- and atomistic-level lipid bilayer simulations. J Chem Phys 2007; 122:244716. [PMID: 16035802 DOI: 10.1063/1.1931651] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A multiscale method is presented to bridge between the atomistic and mesoscopic membrane systems. The atomistic model in this case is the united atom dimyristoylphosphatidylcholine membrane system, although the method is completely general. Atomistic molecular dynamics provides the expansion modulus which is used to parametrize a mesoscopic elastic membrane model. The resulting elastic membrane model, including explicit mesoscopic solvent, shows appropriate static and dynamic undulation behaviors. Large membranes of approximately 100 nm in length can then be easily simulated using the mesoscopic membrane system. The critical feedback from the mesoscopic system back down to the atomistic-scale system is accomplished by bridging the stress (or surface tension) of a small region in the mesoscopic membrane to the corresponding atomistic membrane system. Because of long length-scale modes of membranes such as undulation and buckling, the local tension responds differently from the frame tension, when subjected to external perturbations. The effect of these membrane modes is shown for the stress response of a local membrane region and therefore the atomistic membrane system. In addition, certain equilibrium static and dynamic properties of stand-alone and multiscale coupled systems are presented for several different membrane sizes. Although static properties such as two-dimensional pair-correlation function and order parameters show no noticeable discrepancy for the different systems, lipid self-diffusion and the rotational relaxation of lipid dipoles have a strong dependence on the membrane size (or long-wavelength membrane motions), which is properly modeled by the present multiscale method.
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Affiliation(s)
- Rakwoo Chang
- Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, 84112-0850, USA
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Ulmschneider MB, Ulmschneider JP, Sansom MSP, Di Nola A. A generalized born implicit-membrane representation compared to experimental insertion free energies. Biophys J 2007; 92:2338-49. [PMID: 17218457 PMCID: PMC1864825 DOI: 10.1529/biophysj.106.081810] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An implicit-membrane representation based on the generalized Born theory of solvation has been developed. The method was parameterized against the water-to-cyclohexane insertion free energies of hydrophobic side-chain analogs. Subsequently, the membrane was compared with experimental data from translocon inserted polypeptides and validated by comparison with an independent dataset of six membrane-associated peptides and eight integral membrane proteins of known structure and orientation. Comparison of the insertion energy of alpha-helical model peptides with the experimental values from the biological hydrophobicity scale of Hessa et al. gave a correlation of 93% with a mean unsigned error of 0.64 kcal/mol, when charged residues were ignored. The membrane insertion energy was found to be dependent on residue position. This effect is particularly pronounced for charged and polar residues, which strongly prefer interfacial locations. All integral membrane proteins investigated orient and insert correctly into the implicit-membrane model. Remarkably, the membrane model correctly predicts a partially inserted configuration for the monotopic membrane protein cyclooxygenase, matching experimental and theoretical predictions. To test the applicability and usefulness of the implicit-membrane method, molecular simulations of influenza A M2 as well as the glycophorin A dimer were performed. Both systems remain structurally stable and integrated into the membrane.
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Jójárt B, Martinek TA. Performance of the general amber force field in modeling aqueous POPC membrane bilayers. J Comput Chem 2007; 28:2051-8. [PMID: 17431937 DOI: 10.1002/jcc.20748] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The aim of this work was to answer the question of whether the general amber force field (GAFF) is good enough to simulate fully hydrated POPC membrane bilayers. The test system contained 128 POPC and 2985 TIP3P water molecules. The equilibration was carried out in a nonarbitrary manner to reach the stable liquid-crystalline phase. The simulations were performed by using particle mesh Ewald electrostatics implemented in molecular dynamics packages Amber8 (NPT ensembles) and NAMD2 (NPgammaT ensembles). The computational results were assessed against the following experimental membrane properties: (i) area per lipid, (ii) area compressibility modulus, (iii) order parameter, (iv) gauche conformations per acyl chain, (v) lateral diffusion coefficients, (vi) electron density profile, and (vii) bound water at the lipid/water interface. The analyses revealed that the tested force field combination approximates the experimental values at an unexpectedly good level when the NPgammaT ensemble is applied with a surface tension of 60 mN m(-1) per bilayer. It is concluded that the GAFF/TIP3P combination can be utilized for aqueous membrane bilayer simulations, as it provides acceptable accuracy for biomolecular modeling.
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Affiliation(s)
- Balázs Jójárt
- Department of Chemistry and Chemical Informatics, Faculty of Education, University of Szeged, Boldogasszony sgt. 6, H-6725 Szeged, Hungary
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47
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Vos WL, Vermeer LS, Hemminga MA. Conformation of a peptide encompassing the proton translocation channel of vacuolar H(+)-ATPase. Biophys J 2007; 92:138-46. [PMID: 17040980 PMCID: PMC1697854 DOI: 10.1529/biophysj.106.089854] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Accepted: 09/14/2006] [Indexed: 11/18/2022] Open
Abstract
The structural properties of a crucial transmembrane helix for proton translocation in vacuolar ATPase are studied using double site-directed spin-labeling combined with electron spin resonance (ESR) (or electron paramagnetic resonance) and circular dichroism spectroscopy in sodium dodecyl sulfate micelles. For this purpose, we use a synthetic peptide derived from transmembrane helix 7 of subunit a from the yeast Saccharomyces cerevisiae vacuolar proton-translocating ATPase that contains two natural cysteine residues suitable for spin-labeling. The interspin distance is calculated using a second-moment analysis of the methanethiosulfonate spin-label ESR spectra at 150 K. Molecular dynamics simulation is used to study the effect of the side-chain dynamics and backbone dynamics on the interspin distance. Based on the combined results from ESR, circular dichroism, and molecular dynamics simulation we conclude that the peptide forms a dynamic alpha-helix. We discuss this finding in the light of current models for proton translocation. A novel role for a buried charged residue (H729) is proposed.
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Affiliation(s)
- Werner L Vos
- Laboratory of Biophysics, Wageningen University, Wageningen, The Netherlands
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Baginski M, Czub J, Sternal K. Interaction of amphotericin B and its selected derivatives with membranes: molecular modeling studies. CHEM REC 2007; 6:320-32. [PMID: 17304519 DOI: 10.1002/tcr.20096] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Amphotericin B (AmB) is a well-known antifungal antibiotic that has been used in the clinic for about five decades. Despite its chemotherapeutic importance, AmB is quite toxic and many efforts have been made to improve its pharmacological properties, e.g., by chemical modifications. The lipid membrane is a molecular target for AmB, however, due to heterogeneity of its components, the molecular mechanism of AmB action is still unclear. The lack of this knowledge hinders rational designing of new and less toxic AmB derivatives. Our review is a critical presentation of the current understanding of AmB molecular mechanism of action at the membrane level. Except the experimental approach, the extensive overview of molecular modeling studies, performed mostly in our lab, is presented. The results of interactions between AmB or some of its derivatives and lipid model membranes are discussed. In our studies, different biomembrane models and different associate states of the antibiotic were included. Presented molecular modeling approach is especially valuable with regard to a new paradigm of the structure of lipid membrane containing liquid-ordered domains. Hopefully, all these complementary experimental/computational approaches are going to reach the point at which a new hypothesis about molecular mechanism of AmB activity and selectivity will be put forward.
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Affiliation(s)
- Maciej Baginski
- Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdansk University of Technology, Narutowicza St 11/12, 80-952 Gdansk, Poland.
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Tanizaki S, Feig M. Molecular dynamics simulations of large integral membrane proteins with an implicit membrane model. J Phys Chem B 2006; 110:548-56. [PMID: 16471567 DOI: 10.1021/jp054694f] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The heterogeneous dielectric generalized Born (HDGB) methodology is an the extension of the GBMV model for the simulation of integral membrane proteins with an implicit membrane environment. Three large integral membrane proteins, the bacteriorhodopsin monomer and trimer and the BtuCD protein, were simulated with the HDGB model in order to evaluate how well thermodynamic and dynamic properties are reproduced. Effects of the truncation of electrostatic interactions were examined. For all proteins, the HDGB model was able to generate stable trajectories that remained close to the starting experimental structures, in excellent agreement with explicit membrane simulations. Dynamic properties evaluated through a comparison of B-factors are also in good agreement with experiment and explicit membrane simulations. However, overall flexibility was slightly underestimated with the HDGB model unless a very large electrostatic cutoff is employed. Results with the HDGB model are further compared with equivalent simulations in implicit aqueous solvent, demonstrating that the membrane environment leads to more realistic simulations.
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Affiliation(s)
- Seiichiro Tanizaki
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319, USA
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Bond PJ, Faraldo-Gómez JD, Deol SS, Sansom MSP. Membrane protein dynamics and detergent interactions within a crystal: a simulation study of OmpA. Proc Natl Acad Sci U S A 2006; 103:9518-23. [PMID: 16766663 PMCID: PMC1480439 DOI: 10.1073/pnas.0600398103] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular dynamics (MD) simulations are used to explore the dynamics of a membrane protein in its crystal environment. A 50-ns-duration simulation (at a temperature of 300 K) is performed for the crystallographic unit cell of the bacterial outer membrane protein OmpA. The unit cell contains four protein molecules, plus detergent molecules and water. An excellent correlation between simulated and experimental values of crystallographic B factors is observed. Effectively, 0.2 micros of protein trajectories are obtained, allowing a critical assessment of simulation quality. Some deficiency in conformational sampling is demonstrated, but averaging over multiple trajectories improves this limitation. The previously undescribed structure and dynamics of detergent molecules in a unit cell are reported here, providing insight into the interactions important in the formation and stabilization of the crystalline environment at room temperature. In particular, we show that at room temperature the detergent molecules form a dynamic, extended micellar structure spreading over adjacent OmpA monomers within the crystal.
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Affiliation(s)
- Peter J. Bond
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - José D. Faraldo-Gómez
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Sundeep S. Deol
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Mark S. P. Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
- To whom correspondence should be addressed. E-mail:
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