Dresden 2014 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 21: Membranes and Vesicles II

BP 21.3: Vortrag

Dienstag, 1. April 2014, 14:30–14:45, ZEU 250

Molecular Requirements for Raft Formation in a Lipid/Cholesterol System — •Davit Hakobyan and Andreas Heuer — WWU Münster, Institut für Physikalische Chemie, Münster, Germany

Recent comparison of the MARTINI coarse-grained (CG) bilayer system with an equivalent atomistic system comprised of DPPC, unsaturated dilinoleyl phosphatidylcholine (DUPC) lipids and cholesterol (CHOL) showed very good agreement on the phase separation phenomena [1]. Here the properties of CG lipids and CHOL are systematically varied to study the molecular requirements for the raft formation. The DUPC lipid is assimilated to DPPC lipid by modifying the angles, the angle force constants as well as the bead types of the chains. It turns out that the unmixing is largely driven by van der Waals interactions between DPPC - CHOL/DPPC pairs and is nearly independent of the entropy of the DUPC chains. On the other hand reduction of the angle force constant of DPPC chains by 60 % keeps the system mixed suggesting that the entropic contribution of DPPC chains is important for the unmixing. By substituting the CHOL with shorter and stiffer DPPC-like molecules one observes unmixing similar to DPPC/DUPC/CHOL system which suggests the rigid and flat structure of CHOL to play a key role in raft formation. With a stiffened last bead of CHOL the order of DPPC/CHOL domain significantly increases indicating that the conformational entropy of CHOL is important to prohibit the gelation [2]. 1. Hakobyan, Heuer, J. Phys. Chem. B, 2013, 117, 3841. 2. Hakobyan, Heuer, PLOS ONE, In Press.