Conformations of a charged vesicle interacting with an oppositely charged particle.

Endocytotic and exocytotic processes are usually studied using particle-vesicle systems in theory, but most of them are electroneutral. Nevertheless, charged particle-vesicle systems are much closer to real biological systems. Therefore, wrapping behaviors of a negatively charged vesicle wrapping a positively charged particle are systematically investigated by a series of 2D dynamical simulations in this article. The competition between the elastic bending energy and the electrostatic energy dictates the vesicle configuration and charge distribution. It is found that only for intermediate charge concentrations and small particle sizes a vesicle can completely engulf the particle. When the charge density is high, the interaction between vesicle and particle is unexpectedly weakened by both the hardening effect of the charged membrane and the effective-transportation-frozen effect of the charged components. When the particle is strongly charged, multi-layer folding conformations are observed. These studies may provide important insights into mechanism of endocytotic and exocytotic processes in biological systems.