Biophysical Society Thematic Meeting - October 13-15, 2015

Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling

Poster Abstracts

21-POS Board 21 Understanding Structural Mechanism of β 2 -Adrenergic Receptor Based on Water Molecule Using All-Atom Molecular Dynamics (MD) Simulation Songmi Kim , Changbong Hyeon. Korea Institute for Advanced Study, Seoul , South Korea. G protein-coupled receptors (GPCRs) are membrane proteins and responsible for various cell response including vision, smell, hormones, odorants, neurotransmitter and other factors. The GPCRs have conformational change when binding ligand or signal molecule to transmit signals form extracellular to intercellular regions. Several GPCR crystal structures revealed that the activation of GPCRs is mediated by structural water molecules. To understand structural mechanism focused on water molecules within β 2 -adrenergic receptor (β 2 AR), we constructed systems for different states. We have performed 1μs all-atom MD simulation for each system in membrane environment. The dynamics of water molecule in β 2 AR and structural analysis have been carried out by time correlation function of contacts between residue and water molecules and by calculating the water penetration. Board 24 DMSO Disorders Water Structure and Enhances Water Diffusion Near Phospholipid Bilayer Surfaces Yuno Lee , Changbong Hyeon. Korea Institute of Advanced Study , Seoul, South Korea. Dimethyl sulfoxide (DMSO) prevents ice formation by disrupting the hydrogen bond network among water molecules. Despite its broad use as a cryoprotectant and long-lasting efforts to probe water dynamics in the presence of DMSO, the microscopic underpinnings by which DMSO prevents ice formation on cell surfaces are not fully understood. Here, using all atom molecular dynamics simulations of POPC/water systems at varying DMSO concentrations, we probe the structural and dynamical properties of water and DMSO in the vicinity of phospholipid bilayers. Our study is consistent with the recent studies pointing to DMSO-induced dehyration, but critically reveals the presence of fine structures in hydration layer near bilayer surfaces. DMSO has a unique property that the extent of depletion from solvent-bilayer interfaces, which leads to preserving the hydration layer, is more long-ranged and greater than other cosolvent such as sucrose. As a consequence, the mobility of surface water at increased DMSO concentrations is less affected than that of the bulk water in DMSO solution, enhancing the surface water diffusion relative to the bulk. 24-POS

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