  Biomembranes, which are mainly composed of neutral and charged lipids,
exhibit a large variety of functional structures and dynamics. Here, we report
a coarse-grained molecular dynamics (MD) simulation of the phase separation and
morphological dynamics in charged lipid bilayer vesicles. The screened
long-range electrostatic repulsion among charged head groups delays or inhibits
the lateral phase separation in charged vesicles compared with neutral
vesicles, suggesting the transition of the phase-separation mechanism from
spinodal decomposition to nucleation or homogeneous dispersion. Moreover, the
electrostatic repulsion causes morphological changes, such as pore formation,
and further transformations into disk, string, and bicelle structures, which
are spatiotemporally coupled to the lateral segregation of charged lipids.
Based on our coarse-grained MD simulation, we propose a plausible mechanism of
pore formation at the molecular level. The pore formation in a
charged-lipid-rich domain is initiated by the prior disturbance of the local
molecular orientation in the domain.
