Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 18: Membranes and Vesicles I

BP 18.8: Talk

Wednesday, March 13, 2013, 11:45–12:00, H44

Phase separation in a Lipid/Cholesterol System: Coarse-grained and United-atom Simulations — •Davit Hakobyan and Andreas Heuer — WWU Münster, Institut für Physikalische Chemie, Münster, Germany

The separation of liquid-ordered and liquid-disordered phases of lipids in membranes is a subject of continuous experimental as well as theoretical investigations.

Microscale coarse-grained (CG) and united-atom (UA) simulations are performed to investigate the phase separation of a membrane bilayer for the ternary system of saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and unsaturated 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DUPC) and cholesterol (CHOL). The results of 9 microsecond UA simulation demonstrate the onset of phase separation and are compared with the results of the corresponding CG system. While sharing the structural features of phase separation in the CG model, the onset of de-mixing for the UA model is nearly two orders of magnitude slower. This factor can be rationalized by the different short-time diffusion constants.

Various system properties such as order parameters, lipid - CHOL and CHOL - CHOL interactions are compared between the UA and the CG models. From the structural perspective the phase separation process appears to be rather similar for both models, which illustrates once more the power of using CG approaches. The results are further extended by analysis of different unsaturated lipids, different CHOL concentrations as well as different UA force fields.