Surface viscosities of lipid bilayers determined from equilibrium molecular dynamics simulations

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Author(s)Fitzgerald, James E. III
Author(s)Venable, Richard M.
Author(s)Pastor, Richard W.
Author(s)Lyman, Edward R.
Date Accessioned2023-04-14T14:58:59Z
Date Available2023-04-14T14:58:59Z
Publication Date2023-02-03
DescriptionThis article was originally published in Biophysical Journal. The version of record is available at: https://doi.org/10.1016/j.bpj.2023.01.038. This article will be embargoed until 02/03/2024.
AbstractLipid membrane viscosity is critical to biological function. Bacterial cells grown in different environments alter their lipid composition in order to maintain a specific viscosity, and membrane viscosity has been linked to the rate of cellular respiration. To understand the factors that determine the viscosity of a membrane, we ran equilibrium all-atom simulations of single component lipid bilayers and calculated their viscosities. The viscosity was calculated via a Green-Kubo relation, with the stress-tensor autocorrelation function modeled by a stretched exponential function. By simulating a series of lipids at different temperatures, we establish the dependence of viscosity on several aspects of lipid chemistry, including hydrocarbon chain length, unsaturation, and backbone structure. Sphingomyelin is found to have a remarkably high viscosity, roughly 20 times that of DPPC. Furthermore, we find that inclusion of the entire range of the dispersion interaction increases viscosity by up to 140%. The simulated viscosities are similar to experimental values obtained from the rotational dynamics of small chromophores and from the diffusion of integral membrane proteins but significantly lower than recent measurements based on the deformation of giant vesicles. SIGNIFICANCE: Viscosity is a critical property of cell membranes, actively regulated and known to control the rate of reactions that require the diffusion and encounter of proteins and small molecules. However, experimental measurements span more than an order of magnitude in the obtained viscosity depending on the technique and analysis. Extensive simulations of membrane viscosity are presented in order to make progress toward a unified understanding of membrane viscosity.
SponsorThis paper is dedicated to Klaus Gawrisch. We thank Klaus for setting a high standard, both in science and in character, and for demonstrating how to support younger scientists with positivity and enthusiasm. E.L. and R.W.P. also thank Klaus for insight and experimental support in our studies of liquid ordered phases. E.L. and J.E.F. thank Norm Wagner for suggesting the stretched exp fit as an approach to handle noisy correlation functions in complex fluids. E.L. and J.E.F. were supported by NSF award MCB-2121854, J.E.F. was also supported by NSF award DMR 1935956. Computational work utilized the Extreme Science and Engineering Discovery Environment supported by National Science Foundation Grant ACI-1548562. R.W.P. and R.M.V. were supported by the Intramural Research Program of the NIH, the National Heart, Lung, and Blood Institute, and acknowledge the use of the high-performance computational capabilities at the National Institutes of Health, Bethesda, MD (NHLBI LoBoS cluster).
CitationFitzgerald, James E., Richard M. Venable, Richard W. Pastor, and Edward R. Lyman. “Surface Viscosities of Lipid Bilayers Determined from Equilibrium Molecular Dynamics Simulations.” Biophysical Journal 122, no. 6 (2023): 1094–1104. https://doi.org/10.1016/j.bpj.2023.01.038.
ISSN1542-0086
URLhttps://udspace.udel.edu/handle/19716/32650
Languageen_US
PublisherBiophysical Journal
TitleSurface viscosities of lipid bilayers determined from equilibrium molecular dynamics simulations
TypeArticle
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