1
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Rzycki M, Drabik D. Multifaceted Activity of Fabimycin: Insights from Molecular Dynamics Studies on Bacterial Membrane Models. J Chem Inf Model 2024; 64:4204-4217. [PMID: 38733348 PMCID: PMC11134499 DOI: 10.1021/acs.jcim.4c00228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 04/29/2024] [Accepted: 04/30/2024] [Indexed: 05/13/2024]
Abstract
Membranes─cells' essential scaffolds─are valid molecular targets for substances with an antimicrobial effect. While certain substances, such as octenidine, have been developed to target membranes for antimicrobial purposes, the recently reported molecule, fabimycin (F2B)─a novel agent targeting drug-resistant Gram-negative bacteria─has not received adequate attention regarding its activity on membranes in the literature. The following study aims to investigate the effects of F2B on different bacterial membrane models, including simple planar bilayers and more complex bilayer systems that mimic the Escherichia coli shell equipped with double inner and outer bilayers. Our results show that F2B exhibited more pronounced interactions with bacterial membrane systems compared to the control PC system. Furthermore, we observed significant changes in local membrane property homeostasis in both the inner and outer membrane models, specifically in the case of lateral diffusion, membrane thickness, and membrane resilience (compressibility, tilt). Finally, our results showed that the effect of F2B differed in a complex system and a single membrane system. Our study provides new insights into the multifaceted activity of F2B, demonstrating its potential to disrupt bacterial membrane homeostasis, indicating that its activity extends the currently known mechanism of FabI enzyme inhibition. This disruption, coupled with the ability of F2B to penetrate the outer membrane layers, sheds new light on the behavior of this antimicrobial molecule. This highlights the importance of the interaction with the membrane, crucial in combating bacterial infections, particularly those caused by drug-resistant strains.
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Affiliation(s)
- Mateusz Rzycki
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw 50-370, Poland
| | - Dominik Drabik
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wroclaw 50-370, Poland
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2
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Maity S, Pahari S, Santra S, Jana M. Interfacial Glucose to Regulate Hydrated Lipid Bilayer Properties: Influence of Concentrations. J Chem Inf Model 2024; 64:3841-3854. [PMID: 38635679 DOI: 10.1021/acs.jcim.3c01991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
A series of atomistic molecular dynamics (MD) simulations were carried out with a hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer with the variation of glucose concentrations from 0 to 30 wt % in the presence of 0.3 M NaCl. The study suggested that although the thickness of the lipid bilayer dropped significantly with the increase in glucose concentration, it expanded laterally at high glucose levels due to the intercalation of glucose between the headgroups of adjacent lipids. We adopted the surface assessment via the grid evaluation method to compute the deviation of the bilayer's key structural features for the different amounts of glucose present. This suggested that the accumulation of glucose molecules near the headgroups influences the local lipid bilayer undulation and crimping of the lipid tails. We find that the area compressibility modulus increases with the glucose level, causing enhanced bilayer rigidity arising from the slow lateral diffusion of lipids. The restricted lipid motion at high glucose concentrations controls the sustainability of the curved bilayer surface. Calculations revealed that certain orientations of CO → of interfacial glucose with the PN → of lipid headgroups are preferred, which helps the glucose to form direct hydrogen bonds (HBs) with the lipid headgroups. Such lipid-glucose (LG) HBs relax slowly at low glucose concentrations and exhibit a higher lifetime, whereas fast structural relaxation of LG HBs with a shorter lifetime was noticed at a higher glucose level. In contrast, lipid-water (LW) HBs exhibited a higher lifetime at a higher glucose level, which gradually decreased with the glucose level lowering. The study interprets that the glucose concentration-driven LW and LG interactions are mutually inclusive. Our detailed analysis will exemplify small saccharide concentration-driven membrane stabilizing efficiency, which is, in general, helpful for drug delivery study.
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Affiliation(s)
- Sankar Maity
- Molecular Simulation Laboratory, Department of Chemistry, National Institute of Technology, Rourkela 769008, India
| | - Somdev Pahari
- Molecular Simulation Laboratory, Department of Chemistry, National Institute of Technology, Rourkela 769008, India
| | - Santanu Santra
- Molecular Simulation Laboratory, Department of Chemistry, National Institute of Technology, Rourkela 769008, India
| | - Madhurima Jana
- Molecular Simulation Laboratory, Department of Chemistry, National Institute of Technology, Rourkela 769008, India
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3
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Kumar A, Daschakraborty S. Anomalous lateral diffusion of lipids during the fluid/gel phase transition of a lipid membrane. Phys Chem Chem Phys 2023; 25:31431-31443. [PMID: 37962400 DOI: 10.1039/d3cp04081j] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
A lipid membrane undergoes a phase transition from fluid to gel phase upon changing external thermodynamic conditions, such as decreasing temperature and increasing pressure. Extremophilic organisms face the challenge of preventing this deleterious phase transition. The main focus of their adaptive strategy is to facilitate effective temperature sensing through sensor proteins, relying on the drastic changes in packing density and membrane fluidity during the phase transition. Although the changes in packing density parameters due to the fluid/gel phase transition are studied in detail, the impact on membrane fluidity is less explored in the literature. Understanding the lateral diffusive dynamics of lipids in response to temperature, particularly during the fluid/gel phase transition, is albeit crucial. Here we have simulated the phase transition of a single component lipid membrane composed of dipalmitoylphosphatidylcholine (DPPC) lipids using a coarse-grained (CG) model and studied the changes of the structural and dynamical properties. It is observed that near the phase transition point, both fluid and gel phase domains coexist together. The dynamics remains highly non-Gaussian for a long time even when the mean square displacement reaches the Fickian regime at a much earlier time. This Fickian yet non-Gaussian diffusion (FnGD) is a characteristic of a highly heterogeneous system, previously observed for the lateral diffusion of lipids in raft mimetic membranes having liquid-ordered and liquid-disordered phases co-existing together. We have analyzed the molecular trajectories and calculated the jump-diffusion of the lipids, stemming from sudden jump translations, using a translational jump-diffusion (TJD) approach. An overwhelming contribution of the jump-diffusion of the lipids is observed suggesting anomalous diffusion of lipids during fluid/gel phase transition of the membrane. These results are important in unravelling the intricate nature of lipid diffusion during the phase transition of the membrane and open up a new possibility of investigating the most significant change of membrane properties during phase transition, which can be effectively sensed by proteins.
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Affiliation(s)
- Abhay Kumar
- Department of Chemistry, Indian Institute of Technology Patna, Bihar 801106, India.
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4
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Xu J, Karra V, Large DE, Auguste DT, Hung FR. Understanding the Mechanical Properties of Ultradeformable Liposomes Using Molecular Dynamics Simulations. J Phys Chem B 2023; 127:9496-9512. [PMID: 37879075 PMCID: PMC10641833 DOI: 10.1021/acs.jpcb.3c04386] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 09/19/2023] [Accepted: 10/04/2023] [Indexed: 10/27/2023]
Abstract
Improving drug delivery efficiency to solid tumor sites is a central challenge in anticancer therapeutic research. Our previous experimental study (Guo et al., Nat. Commun. 2018, 9, 130) showed that soft, elastic liposomes had increased uptake and accumulation in cancer cells and tumors in vitro and in vivo respectively, relative to rigid particles. As a first step toward understanding how liposomes' molecular structure and composition modulates their elasticity, we performed all-atom and coarse-grained classical molecular dynamics (MD) simulations of lipid bilayers formed by mixing a long-tailed unsaturated phospholipid with a short-tailed saturated lipid with the same headgroup. The former types of phospholipids considered were 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine (termed here DPMPC). The shorter saturated lipids examined were 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), 1,2-didecanoyl-sn-glycero-3-phosphocholine (DDPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Several lipid concentrations and surface tensions were considered. Our results show that DOPC or DPMPC systems having 25-35 mol % of the shortest lipids DHPC or DDPC are the least rigid, having area compressibility moduli KA that are ∼10% smaller than the values observed in pure DOPC or DPMPC bilayers. These results agree with experimental measurements of the stretching modulus and lysis tension in liposomes with the same compositions. These mixed systems also have lower areas per lipid and form more uneven x-y interfaces with water, the tails of both primary and secondary lipids are more disordered, and the terminal methyl groups in the tails of the long lipid DOPC or DPMPC wriggle more in the vertical direction, compared to pure DOPC or DPMPC bilayers or their mixtures with the longer saturated lipid DLPC or DMPC. These observations confirm our hypothesis that adding increasing concentrations of the short unsaturated lipid DHPC or DDPC to DOPC or DPMPC bilayers alters lipid packing and thus makes the resulting liposomes more elastic and less rigid. No formation of lipid nanodomains was noted in our simulations, and no clear trends were observed in the lateral diffusivities of the lipids as the concentration, type of secondary lipid, and surface tension were varied.
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Affiliation(s)
- Jiaming Xu
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Vyshnavi Karra
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Danielle E. Large
- Department
of Bioengineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Debra T. Auguste
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
- Department
of Bioengineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Francisco R. Hung
- Department
of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, United States
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5
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Glagoleva AA, Yaroslavov AA, Vasilevskaya VV. Computer Simulation Insight into the Adsorption and Diffusion of Polyelectrolytes on Oppositely Charged Surface. Polymers (Basel) 2023; 15:2845. [PMID: 37447491 DOI: 10.3390/polym15132845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/15/2023] Open
Abstract
In the present work, by means of computer simulation, we studied the adsorption and diffusion of polyelectrolyte macromolecules on oppositely charged surfaces. We considered the surface coverage and the charge of the adsorbed layer depending on the ionization degree of the macromolecules and the charge of the surface and carried out a computer experiment on the polymer diffusion within the adsorbed layers, taking into account its strong dependency on the surface coverage and the macromolecular ionization degree. The different regimes were distinguished that provided maximal mobility of the polymer chains along with a high number of charged groups in the layer, which could be beneficial for the development of the functional coatings. The results were compared with those of previous experiments on the adsorption of polyelectrolyte layers that may be applied as biocidal renewable coatings that can reversibly desorb from the surface.
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Affiliation(s)
- Anna A Glagoleva
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia
| | - Alexander A Yaroslavov
- Department of Chemistry, M.V. Lomonosov Moscow State University, 1-3 Leninskie Gory, Moscow 119991, Russia
| | - Valentina V Vasilevskaya
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russia
- Department of Chemistry, M.V. Lomonosov Moscow State University, 1-3 Leninskie Gory, Moscow 119991, Russia
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6
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Scalfi L, Vitali D, Kiefer H, Netz RR. Frequency-dependent hydrodynamic finite size correction in molecular simulations reveals the long-time hydrodynamic tail. J Chem Phys 2023; 158:2890455. [PMID: 37184000 DOI: 10.1063/5.0151406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 04/07/2023] [Indexed: 05/16/2023] Open
Abstract
Finite-size effects are challenging in molecular dynamics simulations because they have significant effects on computed static and dynamic properties, in particular diffusion constants, friction coefficients, and time- or frequency-dependent response functions. We investigate the influence of periodic boundary conditions on the velocity autocorrelation function and the frequency-dependent friction of a particle in a fluid, and show that the long-time behavior (starting at the picosecond timescale) is significantly affected. We develop an analytical correction allowing us to subtract the periodic boundary condition effects. By this, we unmask the power-law long-time tails of the memory kernel and the velocity autocorrelation function in liquid water and a Lennard-Jones fluid from simulations with rather small box sizes.
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Affiliation(s)
- Laura Scalfi
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Domenico Vitali
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Henrik Kiefer
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Roland R Netz
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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7
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Moutoussamy E, Khan HM, Roberts MF, Gershenson A, Chipot C, Reuter N. Standard Binding Free Energy and Membrane Desorption Mechanism for a Phospholipase C. J Chem Inf Model 2022; 62:6602-6613. [PMID: 35343689 PMCID: PMC9795555 DOI: 10.1021/acs.jcim.1c01543] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Peripheral membrane proteins (PMPs) bind temporarily to cellular membranes and play important roles in signaling, lipid metabolism, and membrane trafficking. Obtaining accurate membrane-PMP affinities using experimental techniques is more challenging than for protein-ligand affinities in an aqueous solution. At the theoretical level, calculation of the standard protein-membrane binding free energy using molecular dynamics simulations remains a daunting challenge owing to the size of the biological objects at play, the slow lipid diffusion, and the large variation in configurational entropy that accompanies the binding process. To overcome these challenges, we used a computational framework relying on a series of potential-of-mean-force (PMF) calculations including a set of geometrical restraints on collective variables. This methodology allowed us to determine the standard binding free energy of a PMP to a phospholipid bilayer using an all-atom force field. Bacillus thuringiensis phosphatidylinositol-specific phospholipase C (BtPI-PLC) was chosen due to its importance as a virulence factor and owing to the host of experimental affinity data available. We computed a standard binding free energy of -8.2 ± 1.4 kcal/mol in reasonable agreement with the reported experimental values (-6.6 ± 0.2 kcal/mol). In light of the 2.3-μs separation PMF calculation, we investigated the mechanism whereby BtPI-PLC disengages from interactions with the lipid bilayer during separation. We describe how a short amphipathic helix engages in transitory interactions to ease the passage of its hydrophobes through the interfacial region upon desorption from the bilayer.
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Affiliation(s)
- Emmanuel
E. Moutoussamy
- Department
of Biological Sciences, University of Bergen, N-5020 Bergen, Norway,Computational
Biology Unit, Department of Informatics, University of Bergen, N-5020 Bergen, Norway
| | - Hanif M. Khan
- Department
of Biological Sciences, University of Bergen, N-5020 Bergen, Norway,Computational
Biology Unit, Department of Informatics, University of Bergen, N-5020 Bergen, Norway
| | - Mary F. Roberts
- Department
of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Anne Gershenson
- Department
of Biochemistry and Molecular Biology, University
of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Christophe Chipot
- Laboratoire
International Associé Centre National de la Recherche Scientifique
et University of Illinois at Urbana−Champaign, Unité
Mixte de Recherche n 7019, Université
de Lorraine, BP 70239, 54506 Vandœuvre-lès-Nancy cedex, France,Department
of Physics, University of Illinois, Urbana, Illinois 61801, United States
| | - Nathalie Reuter
- Computational
Biology Unit, Department of Informatics, University of Bergen, N-5020 Bergen, Norway,Department
of Chemistry, University of Bergen, N-5020 Bergen, Norway,
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8
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Laudadio E, Minnelli C, Mobbili G, Sabbatini G, Stipa P, Rusciano D, Galeazzi R. Salt effects on mixed composition membranes containing an antioxidant lipophilic edaravone derivative: a computational-experimental study. Org Biomol Chem 2022; 20:5784-5795. [PMID: 35822625 DOI: 10.1039/d2ob01143c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The protection of lipid membranes against oxidation avoids diseases associated with oxidative stress. As a strategy to contrast it, functionalized lipids with antioxidant activity are used to become part of membranes thus protecting them. For this purpose, a lipophilic edaravone derivative has been synthesized, adding a C18 saturated chain to the original structure. The antioxidant activity of C18-Edv has been demonstrated in our previous work. In this study, molecular dynamics simulations have been performed to define the effects of NaCl, MgCl2, KCl, and CaCl2 salts on a palmitoyl-oleoyl-sn-glycero-phosphocholine (POPC) lipid bilayer encapsulating C18-Edv. The results showed how different salts influence POPC lateral diffusion, and the movements of C18-Edv heads, which are antioxidant moieties, were correlated to the ability of C18-Edv molecules to protect membranes. MgCl2 showed a negative impact leading to C18-Edv clusterization and membrane stretching, while KCl and NaCl showed a moderate influence on the mixed lipid membrane structure. CaCl2 increased the exposure of the C18-Edv heads to the lipid-water interface, resulting in the salt with a higher propensity to guarantee protection against radicals in the aqueous phase. Finally, C18-Edv-POPC liposomes have been prepared following the simulation conditions, and then an experimental Oxygen Radical Absorbance Capacity (ORAC) assay has been performed to confirm the in silico predicted results.
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Affiliation(s)
- Emiliano Laudadio
- Department SIMAU, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - Cristina Minnelli
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
| | - Giovanna Mobbili
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
| | - Giulia Sabbatini
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
| | - Pierluigi Stipa
- Department SIMAU, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - Dario Rusciano
- Research Center, Sooft Italia SpA, 95100, Catania, Italy
| | - Roberta Galeazzi
- Department DISVA, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy.
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9
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Chatterjee P, Sengul MY, Kumar A, MacKerell AD. Harnessing Deep Learning for Optimization of Lennard-Jones Parameters for the Polarizable Classical Drude Oscillator Force Field. J Chem Theory Comput 2022; 18:2388-2407. [PMID: 35362975 PMCID: PMC9097857 DOI: 10.1021/acs.jctc.2c00115] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The outcomes of computational chemistry and biology research, including drug design, are significantly influenced by the underlying force field (FF) used in molecular simulations. While improved FF accuracy may be achieved via inclusion of explicit treatment of electronic polarization, such an extension must be accompanied by optimization of van der Waals (vdW) interactions, in the context of the Lennard-Jones (LJ) formalism in the present study. This is particularly challenging due to the extensive nature of chemical space combined with the correlated nature of LJ parameters. To address this challenge, a deep learning (DL)-based parametrization framework is developed, allowing for sampling of wide ranges of LJ parameters targeting experimental condensed phase thermodynamic properties. The present work utilizes this framework to develop the LJ parameters for atoms associated with four distinct groups covering 10 different atom types. Final parameter selection was facilitated by quantum mechanical data on rare-gas interactions with the training set molecules. The chosen parameters were then validated through experimental hydration free energies and condensed phase thermodynamic properties of validation set molecules to confirm transferability. The ultimate outcome of utilizing this framework is a set of LJ parameters in the context of the polarizable Drude FF, which demonstrated improvement in the reproduction of both experimental pure solvent and crystal properties and hydration free energies of the molecules compared to the additive CHARMM General FF (CGenFF) including the ability of the Drude FF to accurately reproduce both experimental pure solvent properties and hydration free energies. The study also shows how correlations between difference in the reproduction of condensed phase data between model compounds may be used to direct the selection of new atom types and training set molecules during FF development.
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Affiliation(s)
- Payal Chatterjee
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Mert Y Sengul
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Anmol Kumar
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, 20 Penn Street, Baltimore, Maryland 21201, United States
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10
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Minnelli C, Laudadio E, Fiorini R, Galeazzi R, Armeni T, Stipa P, Rusciano D, Mobbili G. Influence of a lipophilic edaravone on physical state and activity of antioxidant liposomes: An experimental and in silico study. Colloids Surf B Biointerfaces 2021; 210:112217. [PMID: 34836703 DOI: 10.1016/j.colsurfb.2021.112217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 11/10/2021] [Accepted: 11/11/2021] [Indexed: 11/16/2022]
Abstract
The influence of a lipophilic derivative of Edaravone (C18Edv) on a POPC liposomal bilayer has been investigated by a combined computational-experimental approach. The order and hydration degree of three different systems composed by 10%, 20% and 40% in w/w percentage of C18Edv respect to POPC were investigated through Molecular Dynamics (MD) simulations and fluorescence spectroscopy experiments. Dynamic Light Scattering measurements showed how the presence of different amounts of C18EdV determines differences on liposome size and stability. The survey revealed that the content of lipophilic antioxidant tunes liposome rigidity and influences cellular uptake and antioxidant activity which are maximized for formulation containing 20% of C18Edv.
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Affiliation(s)
- Cristina Minnelli
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Emiliano Laudadio
- Dipartimento di Scienze e Ingegneria della Materia, dell'Ambiente e Urbanistica (SIMAU), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Rosamaria Fiorini
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Roberta Galeazzi
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Tatiana Armeni
- Dipartimento Scienze Cliniche Specialistiche ed Odontostomatologiche, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Pierluigi Stipa
- Dipartimento di Scienze e Ingegneria della Materia, dell'Ambiente e Urbanistica (SIMAU), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | | | - Giovanna Mobbili
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
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11
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Yu Y, Krämer A, Venable RM, Brooks BR, Klauda JB, Pastor RW. CHARMM36 Lipid Force Field with Explicit Treatment of Long-Range Dispersion: Parametrization and Validation for Phosphatidylethanolamine, Phosphatidylglycerol, and Ether Lipids. J Chem Theory Comput 2021; 17:1581-1595. [PMID: 33620194 PMCID: PMC8130185 DOI: 10.1021/acs.jctc.0c01327] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Long-range Lennard-Jones (LJ) interactions have been incorporated into the CHARMM36 (C36) lipid force field (FF) using the LJ particle-mesh Ewald (LJ-PME) method in order to remove the inconsistency of bilayer and monolayer properties arising from the exclusion of long-range dispersion [Yu, Y.; Semi-automated Optimization of the CHARMM36 Lipid Force Field to Include Explicit Treatment of Long-Range Dispersion. J. Chem. Theory Comput. 2021, 10.1021/acs.jctc.0c01326. (preceding article in this issue)]. The new FF is denoted C36/LJ-PME. While the first optimization was based on three phosphatidylcholines (PCs), this work extends the validation and parametrization to more lipids including PC, phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and ether lipids. The agreement with experimental structure data is excellent for PC, PE, and ether lipids. C36/LJ-PME also compares favorably with scattering data of PG bilayers but less so with NMR deuterium order parameters of 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DMPG) at 303.15 K, indicating a need for future optimization regarding PG-specific parameters. Frequency dependence of NMR T1 spin-lattice relaxation times is well-described by C36/LJ-PME, and the overall agreement with experiment is comparable to C36. Lipid diffusion is slower than C36 due to the added long-range dispersion causing a higher viscosity, although it is still too fast compared to experiment after correction for periodic boundary conditions. When using a 10 Å real-space cutoff, the simulation speed of C36/LJ-PME is roughly equal to C36. While more lipids will be incorporated into the FF in the future, C36/LJ-PME can be readily used for common lipids and extends the capability of the CHARMM FF by supporting monolayers and eliminating the cutoff dependence.
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Affiliation(s)
- Yalun Yu
- Biophysics Graduate Program, University of Maryland, College Park, Maryland 20742, United States
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Andreas Krämer
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Richard M Venable
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Bernard R Brooks
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Jeffery B Klauda
- Biophysics Graduate Program, University of Maryland, College Park, Maryland 20742, United States
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
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12
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Maiti A, Daschakraborty S. Effect of TMAO on the Structure and Phase Transition of Lipid Membranes: Potential Role of TMAO in Stabilizing Cell Membranes under Osmotic Stress. J Phys Chem B 2021; 125:1167-1180. [PMID: 33481606 DOI: 10.1021/acs.jpcb.0c08335] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Extremophiles adopt strategies to deal with different environmental stresses, some of which are severely damaging to their cell membrane. To combat high osmotic stress, deep-sea organisms synthesize osmolytes, small polar organic molecules, like trimethylamine-N-oxide (TMAO), and incorporate them in the cell. TMAO is known to protect cells from high osmotic or hydrostatic pressure. Several experimental and simulation studies have revealed the roles of such osmolytes on stabilizing proteins. In contrast, the effect of osmolytes on the lipid membrane is poorly understood and broadly debated. A recent experiment has found strong evidence of the possible role of TMAO in stabilizing lipid membranes. Using the molecular dynamics (MD) simulation technique, we have demonstrated the effect of TMAO on two saturated fully hydrated lipid membranes in their fluid and gel phases. We have captured the impact of TMAO's concentration on the membrane's structural properties along with the fluid/gel phase transition temperatures. On increasing the concentration of TMAO, we see a substantial increase in the packing density of the membrane (estimated by area, thickness, and volume) and enhancement in the orientational order of lipid molecules. Having repulsive interaction with the lipid head group, the TMAO molecules are expelled away from the membrane surface, which induces dehydration of the lipid head groups, increasing the packing density. The addition of TMAO also increases the fluid/gel phase transition temperature of the membrane. All of these results are in close agreement with the experimental observations. This study, therefore, provides a molecular-level understanding of how TMAO can influence the cell membrane of deep-sea organisms and help in combating the osmotic stress condition.
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Affiliation(s)
- Archita Maiti
- Department of Chemistry, Indian Institute of Technology Patna, Patna, Bihar 801106, India
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13
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Moqadam M, Tubiana T, Moutoussamy EE, Reuter N. Membrane models for molecular simulations of peripheral membrane proteins. ADVANCES IN PHYSICS: X 2021. [DOI: 10.1080/23746149.2021.1932589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- Mahmoud Moqadam
- Department of Chemistry, University of Bergen, Bergen, Norway
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway
| | - Thibault Tubiana
- Department of Chemistry, University of Bergen, Bergen, Norway
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway
| | - Emmanuel E. Moutoussamy
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway
- Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Nathalie Reuter
- Department of Chemistry, University of Bergen, Bergen, Norway
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway
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14
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Gapsys V, de Groot BL. On the importance of statistics in molecular simulations for thermodynamics, kinetics and simulation box size. eLife 2020; 9:57589. [PMID: 32812868 PMCID: PMC7481008 DOI: 10.7554/elife.57589] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Accepted: 08/14/2020] [Indexed: 12/30/2022] Open
Abstract
Computational simulations, akin to wetlab experimentation, are subject to statistical fluctuations. Assessing the magnitude of these fluctuations, that is, assigning uncertainties to the computed results, is of critical importance to drawing statistically reliable conclusions. Here, we use a simulation box size as an independent variable, to demonstrate how crucial it is to gather sufficient amounts of data before drawing any conclusions about the potential thermodynamic and kinetic effects. In various systems, ranging from solvation free energies to protein conformational transition rates, we showcase how the proposed simulation box size effect disappears with increased sampling. This indicates that, if at all, the simulation box size only minimally affects both the thermodynamics and kinetics of the type of biomolecular systems presented in this work.
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Affiliation(s)
- Vytautas Gapsys
- Computational Biomolecular Dynamics Group, Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Bert L de Groot
- Computational Biomolecular Dynamics Group, Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany
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15
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Yu Y, Klauda JB. Update of the CHARMM36 United Atom Chain Model for Hydrocarbons and Phospholipids. J Phys Chem B 2020; 124:6797-6812. [PMID: 32639155 DOI: 10.1021/acs.jpcb.0c04795] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Accurate lipid force field (FF) parameters used in molecular dynamics (MD) simulations are crucial for understanding the properties of lipid-containing systems and biological processes related to lipids. The last update of the CHARMM36 united atom chain model (C36UA) was in 2013 [Lee, S. J. Phys. Chem. B 2014, 118, 547 556]; it utilized CHARMM36 (C36) lipid FF parameters for headgroups and OPLS-UA Lennard-Jones (LJ) parameters for tails. Simulations with the FF were able to reproduce many experimental observables of lipid bilayers accurately, but to be more applicable for a wide range of lipids, additional FF parameter optimization was needed. In this work, we present an update of the model, named C36UAr. The parameterization included the LJ parameters for hydrocarbons and related dihedrals. Bulk liquid properties (density, heat of vaporization, isothermal compressibility, and diffusion constant) of model compounds were used as targets for the LJ parameter fitting, and dihedrals were fit to either quantum mechanical (QM) or potential of mean force (PMF) calculations using C36. Thermodynamic reweighting was used to further improve the parameters. Bilayer simulations of various lipid headgroups (phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol) and tails (saturated, monounsaturated, and polyunsaturated) were performed to validate the model, and significant improvements were seen in bilayer properties, including surface area, membrane thicknesses, NMR deuterium order parameters, and density profiles. C36UAr was also compared to the hydrogen mass repartitioning (HMR) method. The high accuracy and competitive efficiency shown in this study make C36UAr one of the best choices for studies of membrane structure and membrane-associated proteins.
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16
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Andoh Y, Hayakawa S, Okazaki S. Molecular dynamics study of lipid bilayers modeling outer and inner leaflets of plasma membranes of mouse hepatocytes. I. Differences in physicochemical properties between the two leaflets. J Chem Phys 2020; 153:035105. [PMID: 32716170 DOI: 10.1063/5.0012676] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Outer and inner leaflets of plasma cell membranes have different lipid compositions, and the membrane properties of each leaflet can differ from each other significantly due to these composition differences. However, because of the experimental difficulty in measuring the membrane properties for each leaflet separately, the differences are not well understood at a molecular level. In this study, we constructed two lipid bilayer systems, modeling outer and inner leaflets of plasma membranes of mouse hepatocytes based on experimental composition data. The ion concentration in the interlamellar water phase was also set to match the concentration in extra- and intracellular fluids. The differences in physical properties between the outer and inner leaflets of mouse hepatocyte cell membrane models were investigated by performing 1.2 μs-long all-atomistic molecular dynamics calculations under physiological temperature and pressure conditions (310.15 K and 1 atm). The calculated electron density profiles along the bilayer normal for each model bilayer system captured well the asymmetric feature of the experimental electron density profile across actual cell plasma membranes, indicating that our procedure of modeling the outer and inner leaflets of the cell plasma membranes was satisfactory. We found that compared to the outer leaflet model, the inner leaflet model had a very bulky and soft structure in the lateral direction. To confirm the differences, membrane fluidity was measured from the lateral diffusivity and relaxation times. The fluidity was significantly higher in the inner leaflet model than in the outer leaflet model. We also discuss two topics that are of wide interest in biology, i.e., the interdigitation of acyl tails of lipid molecules between two monolayers and the lateral concentration fluctuation of lipid molecules in the bilayers.
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Affiliation(s)
- Yoshimichi Andoh
- Center for Computational Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Shiho Hayakawa
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Susumu Okazaki
- Department of Materials Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
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17
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Yang G, Schubert DW, Nilsson F, Qu M, Redel M. A Study of a Novel Synergy Definition for Ternary CB/CNT Composites Suggesting a Representative Model for CB and CNT. MACROMOL THEOR SIMUL 2020. [DOI: 10.1002/mats.202000035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Guanda Yang
- Institute of Polymer MaterialsFriedrich‐Alexander‐University Erlangen‐Nuremberg Martensstr. 7 Erlangen 91058 Germany
- Bavarian Polymer InstituteKeyLab Advanced Fiber Technology Dr.‐Mack‐Straße 77 Fürth 90762 Germany
| | - Dirk W. Schubert
- Bavarian Polymer InstituteKeyLab Advanced Fiber Technology Dr.‐Mack‐Straße 77 Fürth 90762 Germany
| | - Fritjof Nilsson
- Institute of Polymer MaterialsFriedrich‐Alexander‐University Erlangen‐Nuremberg Martensstr. 7 Erlangen 91058 Germany
- KTH Royal Institute of TechnologySchool of Chemical Science and EngineeringFibre and Polymer Technology Stockholm SE 10044 Sweden
| | - Muchao Qu
- Institute of Polymer MaterialsFriedrich‐Alexander‐University Erlangen‐Nuremberg Martensstr. 7 Erlangen 91058 Germany
- Bavarian Polymer InstituteKeyLab Advanced Fiber Technology Dr.‐Mack‐Straße 77 Fürth 90762 Germany
| | - Michael Redel
- Institute of Polymer MaterialsFriedrich‐Alexander‐University Erlangen‐Nuremberg Martensstr. 7 Erlangen 91058 Germany
- Bavarian Polymer InstituteKeyLab Advanced Fiber Technology Dr.‐Mack‐Straße 77 Fürth 90762 Germany
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18
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Ngo VA, Sarkar S, Neale C, Garcia AE. How Anionic Lipids Affect Spatiotemporal Properties of KRAS4B on Model Membranes. J Phys Chem B 2020; 124:5434-5453. [PMID: 32438809 DOI: 10.1021/acs.jpcb.0c02642] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
RAS proteins are small membrane-anchored GTPases that regulate key cellular signaling networks. It has been recently shown that different anionic lipid types can affect the spatiotemporal properties of RAS through dimerization/clustering and signaling fidelity. To understand the effects of anionic lipids on key spatiotemporal properties of RAS, we dissected 1 ms of data from all-atom molecular dynamics simulations for KRAS4B on two model anionic lipid membranes that have 30% of POPS mixed with neutral POPC and 8% of PIP2 mixed with POPC. We unveiled the orientation space of KRAS4B, whose kinetics were slower and more distinguishable on the membrane containing PIP2 than the membrane containing POPS. Particularly, the PIP2-mixed membrane can differentiate a third kinetic orientation state from the other two known orientation states. We observed that each orientation state may yield different binding modes with an RAF kinase, which is required for activating the MAPK/ERK signaling pathway. However, an overall occluded probability, for which RAF kinases cannot bind KRAS4B, remains unchanged on the two different membranes. We identified rare fast diffusion modes of KRAS4B that appear coupled with orientations exposed to cytosolic RAF. Particularly, on the membrane having PIP2, we found nonlinear correlations between the orientation states and the conformations of the cationic farnesylated hypervariable region, which acts as an anchor in the membrane. Using diffusion coefficients estimated from the all-atom simulations, we quantified the effect of PIP2 and POPS on the KRAS4B dimerization via Green's function reaction dynamics simulations, in which the averaged dimerization rate is 12.5% slower on PIP2-mixed membranes.
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Affiliation(s)
- Van A Ngo
- Center for Nonlinear Studies (CNLS), Los Alamos National Lab, Los Alamos, New Mexico 87545, United States
| | - Sumantra Sarkar
- Center for Nonlinear Studies (CNLS), Los Alamos National Lab, Los Alamos, New Mexico 87545, United States
| | - Chris Neale
- Theoretical Biology and Biophysics Group, T-6, Los Alamos National Lab, Los Alamos, New Mexico 87545, United States
| | - Angel E Garcia
- Center for Nonlinear Studies (CNLS), Los Alamos National Lab, Los Alamos, New Mexico 87545, United States
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19
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Yang A, Moore TC, Iacovella CR, Thompson M, Moore DJ, McCabe C. Examining Tail and Headgroup Effects on Binary and Ternary Gel-Phase Lipid Bilayer Structure. J Phys Chem B 2020; 124:3043-3053. [PMID: 32196346 DOI: 10.1021/acs.jpcb.0c00490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The structural properties of two- and three-component gel-phase bilayers were studied using molecular dynamics simulations. The bilayers contain distearoylphosphatidylcholine (DSPC) phospholipids mixed with alcohols and/or fatty acids of varying tail lengths, with carbon chain lengths of 12, 16, and 24 studied. Changes in both headgroup chemistry and tail length are found to affect the balance between steric repulsion and van der Waals attraction within the bilayers, manifesting in different bilayer structural properties. Lipid components are found to be located at different depths within the bilayer depending on both chain length and headgroup chemistry. The highest bilayer ordering and lowest area per tail are found in systems with medium-length tails. While longer tails can enhance van der Waals attractions, the increased tail-length asymmetry is found to induce disorder and reduce tail packing. Bulkier headgroups further increase steric repulsion, as reflected in increased component offsets and reduced tail packing. These findings help explain how bilayer composition affects the structure of gel-phase bilayers.
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Affiliation(s)
- Alexander Yang
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Timothy C Moore
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Christopher R Iacovella
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Michael Thompson
- GlaxoSmithKline Consumer Health Care, 184 Liberty Corner Road, Suite 200, Warren, New Jersey 07059, United States
| | - David J Moore
- GlaxoSmithKline Consumer Health Care, 184 Liberty Corner Road, Suite 200, Warren, New Jersey 07059, United States
| | - Clare McCabe
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37212, United States.,Multiscale Modeling and Simulation Center, Vanderbilt University, Nashville, Tennessee 37212, United States.,Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37212, United States
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20
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Neale C, García AE. The Plasma Membrane as a Competitive Inhibitor and Positive Allosteric Modulator of KRas4B Signaling. Biophys J 2020; 118:1129-1141. [PMID: 32027820 PMCID: PMC7063485 DOI: 10.1016/j.bpj.2019.12.039] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 12/04/2019] [Accepted: 12/18/2019] [Indexed: 12/31/2022] Open
Abstract
Mutant Ras proteins are important drivers of human cancers, yet no approved drugs act directly on this difficult target. Over the last decade, the idea has emerged that oncogenic signaling can be diminished by molecules that drive Ras into orientations in which effector-binding interfaces are occluded by the cell membrane. To support this approach to drug discovery, we characterize the orientational preferences of membrane-bound K-Ras4B in 1.45-ms aggregate time of atomistic molecular dynamics simulations. Individual simulations probe active or inactive states of Ras on membranes with or without anionic lipids. We find that the membrane orientation of Ras is relatively insensitive to its bound guanine nucleotide and activation state but depends strongly on interactions with anionic phosphatidylserine lipids. These lipids slow Ras' translational and orientational diffusion and promote a discrete population in which small changes in orientation control Ras' competence to bind multiple regulator and effector proteins. Our results suggest that compound-directed conversion of constitutively active mutant Ras into functionally inactive forms may be accessible via subtle perturbations of Ras' orientational preferences at the membrane surface.
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Affiliation(s)
- Chris Neale
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, New Mexico
| | - Angel E García
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico.
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21
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Takeda K, Andoh Y, Shinoda W, Okazaki S. Molecular Behavior of Linear Alkylbenzene Sulfonate in Hydrated Crystal, Tilted Gel, and Liquid Crystal Phases Studied by Molecular Dynamics Simulation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:10877-10884. [PMID: 31355646 DOI: 10.1021/acs.langmuir.9b01607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The lamellar phase produced by surfactants with water exhibits several subphases, such as hydrated crystal (Lc), gel (Lβ), tilted gel (Lβ'), and liquid crystal (Lα) phases, depending on temperature, pressure, and hydration. The dynamics of the surfactant molecules in these phases are still unclear. In the present study, we investigate the translational and conformational dynamics of sodium linear alkylbenzene sulfonate (LAS) molecules in the Lc, Lβ', and Lα phases. In the Lα phase, the lateral diffusion of LAS is as fast as that found for phospholipid bilayers in the Lα phase. The diffusion coefficient was undetectably small for the Lc and Lβ' phases. The conformation of LAS in the Lα phase relaxes very rapidly, whereas those in the Lc and Lβ' phases relax very slowly. The time scale of the relaxations greatly depends on the segment of the LAS molecule for the latter two phases. The relaxation time for the SO3- head group and benzene ring of LAS was much longer than that for alkyl chains. Conformational pattern analyses of LAS alkyl chains revealed that the high fraction of the gauche conformation for the odd-numbered C-C bonds aligns the chain parallel to the bilayer normal and is the main origin of the different relaxation times for different segments in the chain. In the Lc, Lβ', and Lα phases, the orientations of the SO3- group and the benzene ring are locked by the salt bridge among SO3- groups and sodium ions. As a result, the orientational order found for the C-C bonds in the LAS alkyl chains is kept even in the Lα phase.
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Affiliation(s)
- Kosuke Takeda
- Analytical Science Research Laboratories, Kao Corporation , 1334, Minato , Wakayama-Shi, Wakayama 640-8580 , Japan
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22
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Temperature Dependence of the Structure and Dynamics of a Dye-Labeled Lipid in a Planar Phospholipid Bilayer: A Computational Study. J Membr Biol 2019; 252:227-240. [PMID: 31332471 DOI: 10.1007/s00232-019-00081-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 07/11/2019] [Indexed: 10/26/2022]
Abstract
Fluorescent probes are widely employed to label lipids for the investigation of structural and dynamic properties of model and cell membranes through optical microscopy techniques. Although the effect of tagging a lipid with an organic dye is generally assumed to be negligible, optically modified lipids can nonetheless affect the local lipid structure and, in turn, the lipid lateral mobility. To better assess this potential issue, all-atom (MD) molecular dynamics simulations have been performed to study structural and dynamic effects in a model DOPC membrane in the presence of a standard Rhodamine B-labeled DOPE lipid (RHB) as a function of temperature, i.e., 293 K, 303 K, and 320 K. As the temperature is increased, we observe similar changes in the structural properties of both pure DOPC and RHB-DOPC lipid bilayers: an increase of the area per lipid, a reduction of the membrane thickness and a decrease of lipid order parameters. The partial density profile of the RHB headgroups and their orientation within the lipid bilayer confirm the amphiphilic nature of the RHB fluorescent moiety, which mainly partitions in the DOPC glycerol backbone region at each temperature. Moreover, at all temperatures, our results on lipid lateral diffusion support a non-neutral role of the dye with respect to the unlabeled lipid mobility, thus suggesting important implications for optical microscopy studies of lipid membranes.
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23
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Yang G, Nilsson F, Schubert DW. A Study of Finite Size Effects and Periodic Boundary Conditions to Simulations of a Novel Theoretical Self‐Consistent Mean‐Field Approach. MACROMOL THEOR SIMUL 2019. [DOI: 10.1002/mats.201900023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Guanda Yang
- Institute of Polymer MaterialsFriedrich‐Alexander‐University Erlangen‐Nuremberg 91058 Martensstr. 7 Germany
- Bavarian Polymer InstituteKeyLab Advanced Fiber Technology Dr.‐Mack‐Straße 77 90762 Fürth Germany
| | - Fritjof Nilsson
- KTH Royal Institute of TechnologySchool of Chemical Science and EngineeringFibre and Polymer Technology SE‐10044 Stockholm Sweden
| | - Dirk W. Schubert
- Institute of Polymer MaterialsFriedrich‐Alexander‐University Erlangen‐Nuremberg 91058 Martensstr. 7 Germany
- Bavarian Polymer InstituteKeyLab Advanced Fiber Technology Dr.‐Mack‐Straße 77 90762 Fürth Germany
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24
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Abstract
The endogenous lipids N-arachidonylglycine and oleoyl-l-carnitine are potential therapeutic leads in the treatment of chronic pain through their inhibition of the glycine transporter GlyT2. However, their mechanism of action is unknown. It has been hypothesized that these "bioactive" lipids either inhibit GlyT2 indirectly, by significantly perturbing the biophysical properties of the membrane, or directly, by binding directly to the transporter (either from a membrane-exposed or solvent-exposed binding site). Here, we used molecular dynamics simulations to study the effects of the lipids anandamide, N-arachidonylglycine, and oleoyl-l-carnitine on (a) the biophysical properties of the bilayer and (b) direct binding interactions with GlyT2. During the simulations, the biophysical properties of the bilayer itself, for example, the area per lipid, bilayer thickness, and order parameters, were not significantly altered by the presence or type of bioactive lipid, regardless of the presence of GlyT2. Our work, together with previous computational and experimental data, suggests that these acyl-inhibitors of GlyT2 inhibit the transporter by directly binding to it. However, these bioactive lipids bound to various parts of GlyT2 and did not prefer a single binding site during 4.5 μs of simulation. We postulate that the binding site is located at the solvent-exposed regions of GlyT2. Understanding the mechanism of action of these and related bioactive lipids is essential in effectively developing high-affinity GlyT2 inhibitors for the treatment of pain.
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Affiliation(s)
| | - Megan L. O’Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT 2601, Australia
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25
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Leonard AN, Wang E, Monje-Galvan V, Klauda JB. Developing and Testing of Lipid Force Fields with Applications to Modeling Cellular Membranes. Chem Rev 2019; 119:6227-6269. [DOI: 10.1021/acs.chemrev.8b00384] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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26
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Stachura SS, Malajczuk CJ, Kuprusevicius E, Mancera RL. Influence of Bilayer Size and Number in Multi-Bilayer DOPC Simulations at Full and Low Hydration. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:2399-2411. [PMID: 30632763 DOI: 10.1021/acs.langmuir.8b03212] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Biophysical studies of model cell membranes at full and low hydration are usually carried out using scattering measurements on multi-bilayer systems. Molecular simulations of lipid bilayers aimed at reproducing those experimental conditions are usually conducted using single bilayers with different amounts of water. These simulation conditions may lead to artifacts arising from size effects and self-interactions because of periodic boundary conditions. We have tested the influence of the size and number of bilayers on membrane properties using the Lipid14 force field for lipids in molecular dynamics simulations of 1,2-dioleoyl- sn-glycero-3-phosphocholine bilayers at full hydration (44 water molecules per lipid), low hydration (18 water molecules per lipid), and dehydration (9 water molecules per lipid). A number of additional simulations were conducted with the Slipids force field for comparison. We have found that the average area per lipid (APL), thickness, mass density profiles, and acyl tail order parameters are insensitive to the size and the number of bilayers for all hydration states. The Lipid14 force field can also successfully reproduce the experimentally observed decrease in APL and corresponding increase in bilayer thickness upon dehydration, reflecting the increase in ordering as the system becomes more gel-like. Additionally, decreasing hydration levels were associated with a trend away from normal lateral diffusion and toward more subdiffusive regimes across both force fields. In summary, at least for the Lipid14 force field, the use of a single bilayer with 128 phospholipid molecules provides an adequate representation of multi-bilayer systems at varying levels of hydration.
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Affiliation(s)
- Sławomir S Stachura
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute and Curtin Institute for Computation , Curtin University , GPO Box U1987, Perth , Western Australia 6845 , Australia
| | - Chris J Malajczuk
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute and Curtin Institute for Computation , Curtin University , GPO Box U1987, Perth , Western Australia 6845 , Australia
| | - Egidijus Kuprusevicius
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute and Curtin Institute for Computation , Curtin University , GPO Box U1987, Perth , Western Australia 6845 , Australia
| | - Ricardo L Mancera
- School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute and Curtin Institute for Computation , Curtin University , GPO Box U1987, Perth , Western Australia 6845 , Australia
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27
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Jan Akhunzada M, D'Autilia F, Chandramouli B, Bhattacharjee N, Catte A, Di Rienzo R, Cardarelli F, Brancato G. Interplay between lipid lateral diffusion, dye concentration and membrane permeability unveiled by a combined spectroscopic and computational study of a model lipid bilayer. Sci Rep 2019; 9:1508. [PMID: 30728410 PMCID: PMC6365552 DOI: 10.1038/s41598-018-37814-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 12/10/2018] [Indexed: 01/08/2023] Open
Abstract
Lipid lateral diffusion in membrane bilayers is a fundamental process exploited by cells to enable complex protein structural and dynamic reorganizations. For its importance, lipid mobility in both cellular and model bilayers has been extensively investigated in recent years, especially through the application of time-resolved, fluorescence-based, optical microscopy techniques. However, one caveat of fluorescence techniques is the need to use dye-labeled variants of the lipid of interest, thus potentially perturbing the structural and dynamic properties of the native species. Generally, the effect of the dye/tracer molecule is implicitly assumed to be negligible. Nevertheless, in view of the widespread use of optically modified lipids for studying lipid bilayer dynamics, it is highly desirable to well assess this point. Here, fluorescence correlation spectroscopy (FCS) and molecular dynamics (MD) simulations have been combined together to uncover subtle structural and dynamic effects in DOPC planar membranes enriched with a standard Rhodamine-labeled lipid. Our findings support a non-neutral role of the dye-labeled lipids in diffusion experiments, quantitatively estimating a decrease in lipid mobility of up to 20% with respect to the unlabeled species. Moreover, results highlight the existing interplay between dye concentration, lipid lateral diffusion and membrane permeability, thus suggesting possible implications for future optical microscopy studies of biophysical processes occurring at the membrane level.
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Affiliation(s)
- Muhammad Jan Akhunzada
- Scuola Normale Superiore, piazza dei Cavalieri 7, I-56126, Pisa, Italy.,Istituto Nazionale di Fisica Nucleare, Largo Pontecorvo 3, I-56100, Pisa, Italy
| | | | - Balasubramanian Chandramouli
- Scuola Normale Superiore, piazza dei Cavalieri 7, I-56126, Pisa, Italy.,Compunet, Istituto Italiano di Tecnologia (IIT), Via Morego 30, I-16163, Genova, Italy
| | - Nicholus Bhattacharjee
- Scuola Normale Superiore, piazza dei Cavalieri 7, I-56126, Pisa, Italy.,Istituto Nazionale di Fisica Nucleare, Largo Pontecorvo 3, I-56100, Pisa, Italy
| | - Andrea Catte
- Scuola Normale Superiore, piazza dei Cavalieri 7, I-56126, Pisa, Italy.,Istituto Nazionale di Fisica Nucleare, Largo Pontecorvo 3, I-56100, Pisa, Italy
| | - Roberto Di Rienzo
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, Via Girolamo Caruso 16, I-56122 Pisa, Italy
| | - Francesco Cardarelli
- NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, 56127, Pisa, Italy
| | - Giuseppe Brancato
- Scuola Normale Superiore, piazza dei Cavalieri 7, I-56126, Pisa, Italy. .,Istituto Nazionale di Fisica Nucleare, Largo Pontecorvo 3, I-56100, Pisa, Italy.
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28
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Smith DJ, Klauda JB, Sodt AJ. Simulation Best Practices for Lipid Membranes [Article v1.0]. LIVING JOURNAL OF COMPUTATIONAL MOLECULAR SCIENCE 2019; 1:5966. [PMID: 36204133 PMCID: PMC9534443 DOI: 10.33011/livecoms.1.1.5966] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/06/2023]
Abstract
We establish a reliable and robust standardization of settings for practical molecular dynamics (MD) simulations of pure and mixed (single- and multi-component) lipid bilayer membranes. In lipid membranes research, particle-based molecular simulations are a powerful tool alongside continuum theory, lipidomics, and model, in vitro, and in vivo experiments. Molecular simulations can provide precise and reproducible spatiotemporal (atomic- and femtosecond-level) information about membrane structure, mechanics, thermodynamics, kinetics, and dynamics. Yet the simulation of lipid membranes can be a daunting task, given the uniqueness of lipid membranes relative to conventional liquid-liquid and solid-liquid interfaces, the immense and complex thermodynamic and statistical mechanical theory, the diversity of multiscale lipid models, limitations of modern computing power, the difficulty and ambiguity of simulation controls, finite size effects, competitive continuum simulation alternatives, and the desired application, including vesicle experiments and biological membranes. These issues can complicate an essential understanding of the field of lipid membranes, and create major bottlenecks to simulation advancement. In this article, we clarify these issues and present a consistent, thorough, and user-friendly framework for the design of state-of-the-art lipid membrane MD simulations. We hope to allow early-career researchers to quickly overcome common obstacles in the field of lipid membranes and reach maximal impact in their simulations.
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Affiliation(s)
- David J. Smith
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, USA
| | - Jeffery B. Klauda
- Department of Chemical and Biomolecular Engineering and Biophysics Program, University of Maryland, College Park, MD, USA
| | - Alexander J. Sodt
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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29
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Paloncýová M, Ameloot M, Knippenberg S. Orientational distribution of DPH in lipid membranes: a comparison of molecular dynamics calculations and experimental time-resolved anisotropy experiments. Phys Chem Chem Phys 2019; 21:7594-7604. [DOI: 10.1039/c8cp07754a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The behavior of the fluorescent probe diphenylhexatriene (DPH) in different lipid phases is investigated. The rotational autocorrelation functions are calculated in order to model the time-resolved fluorescence anisotropy decay. The role of the order parameters is discussed.
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Affiliation(s)
- Markéta Paloncýová
- Department of Theoretical Chemistry and Biology
- School of Engineering Sciences in Chemistry
- Biotechnology and Health
- Royal Institute of Technology
- Stockholm
| | - Marcel Ameloot
- Biomedical Research Institute, Hasselt University
- 3590 Diepenbeek
- Belgium
| | - Stefan Knippenberg
- Department of Theoretical Chemistry and Biology
- School of Engineering Sciences in Chemistry
- Biotechnology and Health
- Royal Institute of Technology
- Stockholm
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30
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Yu Y, Klauda JB. Modeling Pseudomonas aeruginosa inner plasma membrane in planktonic and biofilm modes. J Chem Phys 2018; 149:215102. [DOI: 10.1063/1.5052629] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Yalun Yu
- Biophysics Graduate Program, University of Maryland, College Park, Maryland 20742, USA
| | - Jeffery B. Klauda
- Biophysics Graduate Program, University of Maryland, College Park, Maryland 20742, USA
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, USA
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31
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Fatehi M, Mohebbi A, Moradi A. Understanding the structural, dynamic and thermodynamic properties of 5-Nonylsalicylaldoxime: Molecular dynamics and experimental studies. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.08.159] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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32
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Lu H, Martí J. Effects of cholesterol on the binding of the precursor neurotransmitter tryptophan to zwitterionic membranes. J Chem Phys 2018; 149:164906. [PMID: 30384712 DOI: 10.1063/1.5029430] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The characterization of the microscopical forces between the essential α-amino-acid tryptophan, precursor of the neurotransmitter serotonin and of the hormone melatonin, and the basic components of cell membranes and their environments (phospholipids, cholesterol, ionic species, and water) is of central importance to elucidate their local structure and dynamics as well as the mechanisms responsible for the access of tryptophan to the interior of the cell. We have performed nanosecond molecular dynamics simulations of tryptophan embedded in model zwitterionic bilayer membranes made by di-palmitoyl-phosphatidyl-choline and cholesterol inside aqueous sodium-chloride solution in order to systematically examine tryptophan-lipid, tryptophan-cholesterol, and tryptophan-water interactions under liquid-crystalline phase conditions. Microscopic properties such as the area per lipid, lipid thickness, radial distribution functions, hydrogen-bonding lengths, atomic spectral densities, and self-diffusion coefficients have been evaluated. Our results show that the presence of tryptophan significantly affects the structure and dynamics of the membrane. Tryptophan spends long periods of time at the water-membrane interface, and it plays a central role by bridging a few lipids and cholesterol chains by means of hydrogen-bonds. The computed spectral densities, in excellent agreement with experimental infrared and Raman data, revealed the participation of each atomic site of tryptophan to the complete spectrum of the molecule. Tryptophan self-diffusion coefficients have been found to be in between 10-7 and 10-6 cm2/s and strongly depending of the concentration of cholesterol in the system.
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Affiliation(s)
- Huixia Lu
- Department of Physics, Technical University of Catalonia-Barcelona Tech, B4-210 Northern Campus UPC, 08034 Barcelona, Catalonia, Spain
| | - Jordi Martí
- Department of Physics, Technical University of Catalonia-Barcelona Tech, B5-209 Northern Campus UPC, 08034 Barcelona, Catalonia, Spain
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33
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Chavent M, Duncan AL, Rassam P, Birkholz O, Hélie J, Reddy T, Beliaev D, Hambly B, Piehler J, Kleanthous C, Sansom MSP. How nanoscale protein interactions determine the mesoscale dynamic organisation of bacterial outer membrane proteins. Nat Commun 2018; 9:2846. [PMID: 30030429 PMCID: PMC6054660 DOI: 10.1038/s41467-018-05255-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 06/15/2018] [Indexed: 01/07/2023] Open
Abstract
The spatiotemporal organisation of membranes is often characterised by the formation of large protein clusters. In Escherichia coli, outer membrane protein (OMP) clustering leads to OMP islands, the formation of which underpins OMP turnover and drives organisation across the cell envelope. Modelling how OMP islands form in order to understand their origin and outer membrane behaviour has been confounded by the inherent difficulties of simulating large numbers of OMPs over meaningful timescales. Here, we overcome these problems by training a mesoscale model incorporating thousands of OMPs on coarse-grained molecular dynamics simulations. We achieve simulations over timescales that allow direct comparison to experimental data of OMP behaviour. We show that specific interaction surfaces between OMPs are key to the formation of OMP clusters, that OMP clusters present a mesh of moving barriers that confine newly inserted proteins within islands, and that mesoscale simulations recapitulate the restricted diffusion characteristics of OMPs. In Escherichia coli, outer membrane protein (OMP) cluster and form islands, but the origin and behaviour of those clusters remains poorly understood. Here authors use coarse grained molecular dynamics simulation and show that their mesoscale simulations recapitulate the restricted diffusion characteristics of OMPs.
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Affiliation(s)
- Matthieu Chavent
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 5RJ, UK.,Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, 205 Route de Narbonne, Toulouse, 31400, France
| | - Anna L Duncan
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 5RJ, UK
| | - Patrice Rassam
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 5RJ, UK.,Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Faculté de Pharmacie, Université de Strasbourg, 74 Route du Rhin, 67401, Illkirch, France
| | - Oliver Birkholz
- Department of Biology, University of Osnabrück, Barbarastraße 11, 49076, Osnabrück, Germany
| | - Jean Hélie
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 5RJ, UK.,SEMMLE, Blue Boar Court, 9 Alfred St, Oxford, OX1 4EH, UK
| | - Tyler Reddy
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 5RJ, UK.,Theoretical Biology and Biophysics, T-6, Los Alamos National Laboratory, Los Alamos, NM, 87525, USA
| | - Dmitry Beliaev
- Mathematical Institute, University of Oxford, Andrew Wiles Building, Radcliffe Observatory Quarter (550), Woodstock Road, Oxford, OX2 6GG, UK
| | - Ben Hambly
- Mathematical Institute, University of Oxford, Andrew Wiles Building, Radcliffe Observatory Quarter (550), Woodstock Road, Oxford, OX2 6GG, UK
| | - Jacob Piehler
- Department of Biology, University of Osnabrück, Barbarastraße 11, 49076, Osnabrück, Germany
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 5RJ, UK.
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 5RJ, UK.
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34
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Laudadio E, Minnelli C, Amici A, Massaccesi L, Mobbili G, Galeazzi R. Liposomal Formulations for an Efficient Encapsulation of Epigallocatechin-3-gallate: An in- Silico/Experimental Approach. Molecules 2018; 23:molecules23020441. [PMID: 29462955 PMCID: PMC6017453 DOI: 10.3390/molecules23020441] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 02/07/2018] [Accepted: 02/13/2018] [Indexed: 01/29/2023] Open
Abstract
As a part of research project aimed to optimize antioxidant delivery, here we studied the influence of both salts and lipid matrix composition on the interaction of epigallocatechin-3-gallate (EGCG) with bilayer leaflets. Thus, we combined in silico and experimental methods to study the ability of neutral and anionic vesicles to encapsulate EGCG in the presence of Ca2+ and Mg2+ divalent salts. Experimental and in silico results show a very high correlation, thus confirming the efficiency of the developed methodology. In particular, we found out that the presence of calcium ions hinders the insertion of EGCG in the liposome bilayer in both neutral and anionic systems. On the contrary, the presence of MgCl2 improves the insertion degree of EGCG molecules respect to the liposomes without divalent salts. The best and most efficient salt concentration is that corresponding to a 5:1 molar ratio between Mg2+ and EGCG, in both neutral and anionic vesicles. Concerning the lipid matrix composition, the anionic one results in better promotion of the catechin insertion within the bilayer since experimentally we achieved 100% EGCG encapsulation in the lipid carrier in the presence of a 5:1 molar ratio of magnesium. Thus, the combination of this anionic liposomal formulation with magnesium chloride, avoids time-consuming separation steps of unentrapped active principle and appears particularly suitable for EGCG delivery applications.
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Affiliation(s)
- Emiliano Laudadio
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
| | - Cristina Minnelli
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
| | - Adolfo Amici
- Dipartimento Scienze Cliniche Specialistiche ed Odontostomatologiche, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
| | - Luca Massaccesi
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
| | - Giovanna Mobbili
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
| | - Roberta Galeazzi
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
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35
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Piggot TJ, Allison JR, Sessions RB, Essex JW. On the Calculation of Acyl Chain Order Parameters from Lipid Simulations. J Chem Theory Comput 2017; 13:5683-5696. [PMID: 28876925 DOI: 10.1021/acs.jctc.7b00643] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
For molecular dynamics simulations of biological membrane systems to live up to the potential of providing accurate atomic level detail into membrane properties and functions, it is essential that the force fields used to model such systems are as accurate as possible. One membrane property that is often used to assess force field accuracy is the carbon-hydrogen (or carbon-deuterium) order parameters of the lipid tails, which can be accurately measured using experimental NMR techniques. There are a variety of analysis tools available to calculate these order parameters from simulations and it is essential that these computational tools work correctly to ensure the accurate assessment of the simulation force fields. In this work we compare many of these computational tools for calculating the order parameters of POPC membranes. While tools that work on all-atom systems and tools that work on saturated lipid tails in general work extremely well, we demonstrate that the majority of the tested tools that calculate the order parameters for unsaturated united-atom lipid tails do so incorrectly. We identify tools that do perform accurate calculations and include one such program with this work, enabling rapid and accurate calculation of united-atom lipid order parameters. Furthermore, we discuss cases in which it is nontrivial to appropriately predict the unsaturated carbon order parameters in united-atom systems. Finally, we examine order parameter splitting for carbon 2 in sn-2 lipid chains, demonstrating substantial deviations from experimental values in several all-atom and united-atom lipid force fields.
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Affiliation(s)
- Thomas J Piggot
- Chemical, Biological and Radiological Sciences, Defence Science and Technology Laboratory , Porton Down, Salisbury, Wiltshire SP4 0JQ, U.K.,Chemistry, University of Southampton , Highfield, Southampton SO17 1BJ, U.K
| | - Jane R Allison
- Centre for Theoretical Chemistry and Physics, Institute of Natural and Mathematical Sciences, Massey University , Auckland 0632, New Zealand
| | - Richard B Sessions
- School of Biochemistry, University of Bristol , University Walk, Bristol BS8 1TD, U.K
| | - Jonathan W Essex
- Chemistry, University of Southampton , Highfield, Southampton SO17 1BJ, U.K
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36
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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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37
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Laudadio E, Mobbili G, Minnelli C, Massaccesi L, Galeazzi R. Salts Influence Cathechins and Flavonoids Encapsulation in Liposomes: A Molecular Dynamics Investigation. Mol Inform 2017. [PMID: 28635075 DOI: 10.1002/minf.201700059] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cathechins and flavonoids are responsible of numerous health benefits. Two of the most representatives' compounds for their antioxidant and therapeutic effects are Epigallocatechin 3-Gallate (EGCG), from green tea extracts, and morelloflavone (MF), from Garcinia dulcis. Here we explore, by atomistic Molecular Dynamics simulations, how EGCG and MF interact with lipid bilayers and we show the salts' influence on their encapsulation degree in neutral liposomes. As a result, we found out that EGCGs naturally bind to the hydrophilic regions of phospholipids, positioning themselves mostly at the interface between water and lipid phases. The presence of a salt clearly influences the EGCG molecules' absorption and the total effect depends strongly on the salt nature and concentration. Beside, for MF, we observed a high stability of the intermolecular MFs aggregates in water that strongly penalizes the flavonoid's interaction with the lipid polar heads. However, salts can influence MF's liposomal penetration, even if they are not able to promote completely its absorption inside the bilayer. For both compounds, the increase of penetration is more marked in presence of magnesium chloride, whilst calcium chloride showed the opposite effect.
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Affiliation(s)
- Emiliano Laudadio
- Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, 60131, Ancona -, ITALY
| | - Giovanna Mobbili
- Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, 60131, Ancona -, ITALY
| | - Cristina Minnelli
- Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, 60131, Ancona -, ITALY
| | - Luca Massaccesi
- Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, 60131, Ancona -, ITALY
| | - Roberta Galeazzi
- Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, via Brecce Bianche, 60131, Ancona -, ITALY
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38
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Balusek C, Gumbart JC. Role of the Native Outer-Membrane Environment on the Transporter BtuB. Biophys J 2017; 111:1409-1417. [PMID: 27705764 DOI: 10.1016/j.bpj.2016.08.033] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 08/22/2016] [Accepted: 08/26/2016] [Indexed: 11/19/2022] Open
Abstract
BtuB is a TonB-dependent transporter that permits the high-affinity binding and transport of cobalamin (CBL), or vitamin B12, across the asymmetric outer membrane (OM) of Gram-negative bacteria. It has been shown that Ca2+ binding is necessary for high-affinity binding of CBL to BtuB, and earlier simulations suggested that calcium ions serve to stabilize key substrate-binding extracellular loops. However, those simulations did not account for the lipopolysaccharides in the OM. To illuminate the roles of both Ca2+ and lipopolysaccharides in protein functionality, we performed simulations of apo and Ca2+-loaded BtuB in symmetric and asymmetric bilayers. The simulations reveal that the oligosaccharides of LPS stabilize the extracellular loops to some degree, apparently obviating the need for Ca2+. However, it is shown that Ca2+ ions stabilize a key substrate-binding loop to an even greater degree, as well as reposition specific CBL-binding residues, bringing them closer to the organization found in the CBL-bound structure. These results indicate the importance of including realistic membrane models when simulating outer-membrane proteins.
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Affiliation(s)
- Curtis Balusek
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia
| | - James C Gumbart
- School of Physics, Georgia Institute of Technology, Atlanta, Georgia.
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39
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Vermaas JV, Pogorelov TV, Tajkhorshid E. Extension of the Highly Mobile Membrane Mimetic to Transmembrane Systems through Customized in Silico Solvents. J Phys Chem B 2017; 121:3764-3776. [PMID: 28241729 PMCID: PMC5558153 DOI: 10.1021/acs.jpcb.6b11378] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanics of the protein-lipid interactions of transmembrane proteins are difficult to capture with conventional atomic molecular dynamics, due to the slow lateral diffusion of lipids restricting sampling to states near the initial membrane configuration. The highly mobile membrane mimetic (HMMM) model accelerates lipid dynamics by modeling the acyl tails nearest to the membrane center as a fluid organic solvent while maintaining an atomic description of the lipid headgroups and short acyl tails. The HMMM has been applied to many peripheral protein systems; however, the organic solvent used to date caused deformations in transmembrane proteins by intercalating into the protein and disrupting interactions between individual side chains. We ameliorate the effect of the solvent on transmembrane protein structure through the development of two new in silico Lennard-Jones solvents. The parameters for the new solvents were determined through an extensive parameter search in order to match the bulk properties of alkanes in a highly simplified model. Using these new solvents, we substantially improve the insertion free energy profiles of 10 protein side chain analogues across the entire bilayer. In addition, we reduce the intercalation of solvent into transmembrane systems, resulting in native-like transmembrane protein structures from five different topological classes within a HMMM bilayer. The parametrization of the solvents, in addition to their computed physical properties, is discussed. By combining high lipid lateral diffusion with intact transmembrane proteins, we foresee the developed solvents being useful to efficiently identify membrane composition inhomogeneities and lipid binding caused by the presence of membrane proteins.
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Affiliation(s)
- Josh V Vermaas
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Taras V Pogorelov
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
- Department of Chemistry, School of Chemical Sciences, National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Emad Tajkhorshid
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
- Department of Biochemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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40
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Hakobyan D, Heuer A. 2D lattice model of a lipid bilayer: Microscopic derivation and thermodynamic exploration. J Chem Phys 2017; 146:064305. [DOI: 10.1063/1.4975163] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Davit Hakobyan
- Institute of Physical Chemistry, WWU Münster, Corrensstr. 28/30, 48149 Münster, Germany and Center for Multiscale Theory and Computation (CMTC), WWU Münster, 48149 Münster, Germany
| | - Andreas Heuer
- Institute of Physical Chemistry, WWU Münster, Corrensstr. 28/30, 48149 Münster, Germany and Center for Multiscale Theory and Computation (CMTC), WWU Münster, 48149 Münster, Germany
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41
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Andoh Y, Aoki N, Okazaki S. Molecular dynamics study of lipid bilayers modeling the plasma membranes of mouse hepatocytes and hepatomas. J Chem Phys 2016; 144:085104. [PMID: 26931728 DOI: 10.1063/1.4942159] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Molecular dynamics (MD) calculations of lipid bilayers modeling the plasma membranes of normal mouse hepatocytes and hepatomas in water have been performed under physiological isothermal-isobaric conditions (310.15 K and 1 atm). The changes in the membrane properties induced by hepatic canceration were investigated and were compared with previous MD calculations included in our previous study of the changes in membrane properties induced by murine thymic canceration. The calculated model membranes for normal hepatocytes and hepatomas comprised 23 and 24 kinds of lipids, respectively. These included phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, lysophospholipids, and cholesterol. We referred to previously published experimental values for the mole fraction of the lipids adopted in the present calculations. The calculated structural and dynamic properties of the membranes such as lateral structure, order parameters, lateral self-diffusion constants, and rotational correlation times all showed that hepatic canceration causes plasma membranes to become more ordered laterally and less fluid. Interestingly, this finding contrasts with the less ordered structure and increased fluidity of plasma membranes induced by thymic canceration observed in our previous MD study.
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Affiliation(s)
- Yoshimichi Andoh
- Center of Computational Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Noriyuki Aoki
- Department of Applied Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
| | - Susumu Okazaki
- Center of Computational Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
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42
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Hoiles W, Gupta R, Cornell B, Cranfield C, Krishnamurthy V. The Effect of Tethers on Artificial Cell Membranes: A Coarse-Grained Molecular Dynamics Study. PLoS One 2016; 11:e0162790. [PMID: 27736860 PMCID: PMC5063460 DOI: 10.1371/journal.pone.0162790] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 08/29/2016] [Indexed: 11/18/2022] Open
Abstract
Tethered bilayer lipid membranes (tBLMs) provide a stable platform for modeling the dynamics and order of biological membranes where the tethers mimic the cytoskeletal supports present in biological cell membranes. In this paper coarse-grained molecular dynamics (CGMD) is applied to study the effects of tethers on lipid membrane properties. Using results from the CGMD model and the overdamped Fokker-Planck equation, we show that the diffusion tensor and particle density of water in the tBLM is spatially dependent. Further, it is shown that the membrane thickness, lipid diffusion, defect density, free energy of lipid flip-flop, and membrane dielectric permittivity are all dependent on the tether density. The numerically computed results from the CGMD model are in agreement with the experimentally measured results from tBLMs containing different tether densities and lipids derived from Archaebacteria. Additionally, using experimental measurements from Escherichia coli bacteria and Saccharomyces Cerevisiae yeast tethered membranes, we illustrate how previous molecular dynamics results can be combined with the proposed model to estimate the dielectric permittivity and defect density of these membranes as a function of tether density.
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Affiliation(s)
- William Hoiles
- Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Rini Gupta
- Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Bruce Cornell
- Director of Science and Technology, Surgical Diagnostics Pty Ltd., Unit 6 30-32 Barcoo Street, Roseville, New South Wales, 2069, Australia
| | - Charles Cranfield
- School of Life Sciences, University of Technology Sydney, Broadway, New South Wales, Australia
| | - Vikram Krishnamurthy
- Electrical and Computer Engineering, Cornell University, New York, New York, United States of America
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43
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Camley BA, Lerner MG, Pastor RW, Brown FLH. Strong influence of periodic boundary conditions on lateral diffusion in lipid bilayer membranes. J Chem Phys 2016; 143:243113. [PMID: 26723598 DOI: 10.1063/1.4932980] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Saffman-Delbrück hydrodynamic model for lipid-bilayer membranes is modified to account for the periodic boundary conditions commonly imposed in molecular simulations. Predicted lateral diffusion coefficients for membrane-embedded solid bodies are sensitive to box shape and converge slowly to the limit of infinite box size, raising serious doubts for the prospects of using detailed simulations to accurately predict membrane-protein diffusivities and related transport properties. Estimates for the relative error associated with periodic boundary artifacts are 50% and higher for fully atomistic models in currently feasible simulation boxes. MARTINI simulations of LacY membrane protein diffusion and LacY dimer diffusion in DPPC membranes and lipid diffusion in pure DPPC bilayers support the underlying hydrodynamic model.
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Affiliation(s)
- Brian A Camley
- Center for Theoretical Biological Physics and Department of Physics, University of California, San Diego, California 92093, USA
| | - Michael G Lerner
- Department of Physics and Astronomy, Earlham College, Richmond, Indiana 47374, USA
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Frank L H Brown
- Department of Physics, University of California, Santa Barbara, California 93106, USA
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44
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An extensive simulation study of lipid bilayer properties with different head groups, acyl chain lengths, and chain saturations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:3093-3104. [PMID: 27664502 DOI: 10.1016/j.bbamem.2016.09.016] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/14/2016] [Accepted: 09/19/2016] [Indexed: 12/21/2022]
Abstract
Previous MD simulations of six phosphocholine (PC) lipid bilayers demonstrated the accuracy of the CHARMM36 force field (C36FF) for PC bilayer simulation at varied temperatures (BBA-Biomembranes, 1838 (2014): 2520-2529). In this work, we further examine the accuracy of C36FF over a wide temperature range for a broader range of lipid types such as various head groups (phosphatidic acid (PA), PC, phosphoethanolamine (PE), phosphoglycerol (PG), and phosphoserine (PS)), and tails (saturated, mono-, mixed- and poly-unsaturated acyl chains with varied chain lengths). The structural properties (surface area per lipid (SA/lip), overall bilayer thickness, hydrophobic thickness, headgroup-to-headgroup thickness, deuterium order parameter (SCD), and spin-lattice relaxation time (T1)) obtained from simulations agree well with nearly all available experimental data. Our analyses indicate that PS lipids have the most inter-lipid hydrogen bonds, while PG lipids have the most intra-lipid hydrogen bonds, which play the main role in their low SA/lip in PS lipids and low thicknesses in PG lipids, respectively. PS, PE, and PA lipids have the largest contact clusters with on average 5-8 lipids per cluster, while PC and PG have clusters of 4 lipids based on a cutoff distance of 6.5Å. PS lipids have much slower lipid wobble (i.e., higher correlation time) than other head groups at a given temperature as the hydrogen bonded network significantly reduces a lipid's mobility, and the rate of lipid wobble increases dramatically as temperature increases. These in-depth analyses facilitate further understanding of lipid bilayers at the atomic level.
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45
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Kapla J, Stevensson B, Maliniak A. Coarse-Grained Molecular Dynamics Simulations of Membrane–Trehalose Interactions. J Phys Chem B 2016; 120:9621-31. [DOI: 10.1021/acs.jpcb.6b06566] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Jon Kapla
- Department of Materials and
Environmental Chemistry, Arrhenius Laboratory, Stockholm University, 106
91 Stockholm, Sweden
| | - Baltzar Stevensson
- Department of Materials and
Environmental Chemistry, Arrhenius Laboratory, Stockholm University, 106
91 Stockholm, Sweden
| | - Arnold Maliniak
- Department of Materials and
Environmental Chemistry, Arrhenius Laboratory, Stockholm University, 106
91 Stockholm, Sweden
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46
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Divergent Diffusion Coefficients in Simulations of Fluids and Lipid Membranes. J Phys Chem B 2016; 120:8722-32. [DOI: 10.1021/acs.jpcb.6b05102] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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47
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Conformational Heterogeneity of Bax Helix 9 Dimer for Apoptotic Pore Formation. Sci Rep 2016; 6:29502. [PMID: 27381287 PMCID: PMC4933972 DOI: 10.1038/srep29502] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 06/20/2016] [Indexed: 11/27/2022] Open
Abstract
Helix α9 of Bax protein can dimerize in the mitochondrial outer membrane (MOM) and lead to apoptotic pores. However, it remains unclear how different conformations of the dimer contribute to the pore formation on the molecular level. Thus we have investigated various conformational states of the α9 dimer in a MOM model — using computer simulations supplemented with site-specific mutagenesis and crosslinking of the α9 helices. Our data not only confirmed the critical membrane environment for the α9 stability and dimerization, but also revealed the distinct lipid-binding preference of the dimer in different conformational states. In our proposed pathway, a crucial iso-parallel dimer that mediates the conformational transition was discovered computationally and validated experimentally. The corroborating evidence from simulations and experiments suggests that, helix α9 assists Bax activation via the dimer heterogeneity and interactions with specific MOM lipids, which eventually facilitate proteolipidic pore formation in apoptosis regulation.
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48
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Poger D, Caron B, Mark AE. Validating lipid force fields against experimental data: Progress, challenges and perspectives. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1556-65. [DOI: 10.1016/j.bbamem.2016.01.029] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 01/07/2016] [Accepted: 01/27/2016] [Indexed: 01/16/2023]
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49
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Baylon JL, Vermaas JV, Muller MP, Arcario MJ, Pogorelov TV, Tajkhorshid E. Atomic-level description of protein-lipid interactions using an accelerated membrane model. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1858:1573-83. [PMID: 26940626 PMCID: PMC4877275 DOI: 10.1016/j.bbamem.2016.02.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 02/19/2016] [Accepted: 02/20/2016] [Indexed: 01/03/2023]
Abstract
Peripheral membrane proteins are structurally diverse proteins that are involved in fundamental cellular processes. Their activity of these proteins is frequently modulated through their interaction with cellular membranes, and as a result techniques to study the interfacial interaction between peripheral proteins and the membrane are in high demand. Due to the fluid nature of the membrane and the reversibility of protein-membrane interactions, the experimental study of these systems remains a challenging task. Molecular dynamics simulations offer a suitable approach to study protein-lipid interactions; however, the slow dynamics of the lipids often prevents sufficient sampling of specific membrane-protein interactions in atomistic simulations. To increase lipid dynamics while preserving the atomistic detail of protein-lipid interactions, in the highly mobile membrane-mimetic (HMMM) model the membrane core is replaced by an organic solvent, while short-tailed lipids provide a nearly complete representation of natural lipids at the organic solvent/water interface. Here, we present a brief introduction and a summary of recent applications of the HMMM to study different membrane proteins, complementing the experimental characterization of the presented systems, and we offer a perspective of future applications of the HMMM to study other classes of membrane proteins. This article is part of a Special Issue entitled: Membrane proteins edited by J.C. Gumbart and Sergei Noskov.
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Affiliation(s)
- Javier L Baylon
- Center for Biophysics and Quantitative Biology; Beckman Institute for Advanced Science and Technology.
| | - Josh V Vermaas
- Center for Biophysics and Quantitative Biology; Beckman Institute for Advanced Science and Technology.
| | - Melanie P Muller
- Center for Biophysics and Quantitative Biology; Beckman Institute for Advanced Science and Technology; College of Medicine.
| | - Mark J Arcario
- Center for Biophysics and Quantitative Biology; Beckman Institute for Advanced Science and Technology; College of Medicine.
| | - Taras V Pogorelov
- Beckman Institute for Advanced Science and Technology; School of Chemical Sciences; Department of Chemistry; National Center for Supercomputing Applications.
| | - Emad Tajkhorshid
- Center for Biophysics and Quantitative Biology; Beckman Institute for Advanced Science and Technology; College of Medicine; Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
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50
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Park S, Beaven AH, Klauda JB, Im W. How Tolerant are Membrane Simulations with Mismatch in Area per Lipid between Leaflets? J Chem Theory Comput 2016; 11:3466-77. [PMID: 26575780 PMCID: PMC4685941 DOI: 10.1021/acs.jctc.5b00232] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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Difficulties in estimating the correct
number of lipids in each
leaflet of complex bilayer membrane simulation systems make it inevitable
to introduce a mismatch in lipid packing (i.e., area per lipid) and
thus alter the lateral pressure of each leaflet. To investigate potential
impacts of such mismatch on simulation results, we performed molecular
dynamics simulations of saturated and monounsaturated lipid bilayers
with and without gramicidin A or WALP23 at various mismatches by adjusting
the number of lipids in the lower leaflet from no mismatch to a 25%
reduction compared to that in the upper leaflet. All simulations were
stable under the constant pressure barostat, but the mismatch induces
asymmetric lipid packing between the leaflets, so that the upper leaflet
becomes more ordered, and the lower leaflet becomes less ordered.
The mismatch impacts on various bilayer properties are mild up to
5–10% mismatch, and bilayers with fully saturated chains appear
to be more prone to these impacts than those with unsaturated tails.
The nonvanishing leaflet surface tensions and the free energy derivatives
with respect to the bilayer curvature indicate that the bilayer would
be energetically unstable in the presence of mismatch. We propose
a quantitative criterion for allowable mismatch based on the energetics
derived from a continuum elastic model, which grows as a square root
of the number of the lipids in the system. On the basis of this criterion,
we infer that the area per lipid mismatch up to 5% would be tolerable
in various membrane simulations of reasonable all-atom system sizes
(40–160 lipids per leaflet).
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Affiliation(s)
| | | | - Jeffery B Klauda
- Department of Chemical and Biomolecular Engineering and the Biophysics Program, University of Maryland , College Park, Maryland 20742, United States
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