Biophysical Society Thematic Meeting - October 13-15, 2015

Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling

Poster Abstracts

27-POS Board 27 Replica-Exchange Molecular-Dynamics Simulations of Mixed Lipid Bilayer Systems Takaharu Mori , Yuji Sugita. RIKEN, Wako-shi, Saitama, Japan. Conformational sampling is fundamentally important for simulating complex bio-molecular systems. The generalized-ensemble algorithm, especially the temperature replica-exchange molecular dynamics method (T-REMD), is one of the most powerful methods to explore structures of bio-molecules such as proteins, nucleic acids, carbohydrates, and also of lipid membranes. Recently, we have proposed a new generalized-ensemble algorithm for membrane systems, which we call the surface-tension REMD method (γ-REMD) [1]. Each replica is simulated in the NPγT ensemble, and surface tensions in a pair of replicas are exchanged at certain intervals to enhance conformational sampling of the target membrane system. In this study, we carried out γ-REMD simulation for a pure DPPC lipid bilayer [1], and also T-REMD, γ-REMD, and γT-REMD simulations for a mixed POPC/DMPC lipid bilayer [2]. In the DPPC simulation, we found that lateral diffusion of lipid molecules was enhanced compared with conventional MD simulation. In the POPC/DMPC simulations, lateral diffusion in the same lipid phase was enhanced in all REMD simulations. As for "mixing" of two lipid components, however, it was enhanced in T-REMD, while it was suppressed in γ-REMD. In γT-REMD, both enhancement and suppression were observed, presumably because lateral diffusion is accelerated at high temperature while it is suppressed under high surface tension. We suggest that surface tension affects the degree of mixing of lipid components in biological membranes. [1] T. Mori, J. Jung, and Y. Sugita, J. Chem. Theory Comput., 9, 5629-5640 (2013). [2] J. Jung, T. Mori, C. Kobayashi, Y. Matsunaga, T. Yoda, M. Feig, and Y. Sugita , WIREs Comput. Mol. Sci., doi: 10.1002/wcms.1220 (2015).

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