Formation Mechanism of Lipid Membrane and Vesicle Using Small Angle X-ray Scattering and Dissipative Particle Dynamics (DPD) Method

Abstract

In order to perform efficient nanoparticle design in drug delivery systems, prediction of physical properties and elucidation of the molecular mechanism are expected by using molecular simulation. In this study, we investigated the molecular mechanism of lipid bilayer formation and mixed lipid vesicle formation using the dissipative particle dynamics (DPD) method and small angle X-ray scattering measurement. Parameters of inter-molecular interaction used for the DPD simulation were estimated in quantum mechanical level by the fragment molecular orbital method (FMO-DPD method). In lipid bilayer formation, it was found that the phospholipid having an unsaturated bond (DOPC) has higher membrane fluidity than the phospholipid (DPPC) having only saturated bonds. In the vesicle formation mixed with phospholipid and positively charged lipid, it was also found that as the proportion of positively charged lipid increases, the fluidity of the membrane increases and the shape changes from a sphere to a flat sphere.