メゾスケールシミュレーション手法による生体膜内の分子拡散の解析

抄録

Biomembranes are composed of various types of lipids and proteins and are generally known to be laterally heterogeneous. In biomembranes, the heterogeneous field is formed via a phase separation into the ordered Lo domain, which is rich in saturated lipids and cholesterol, and the disordered Ld domain, which is rich in unsaturated lipids and is fluid. In particular, the Lo domain is called a lipid raft and plays important roles in cell functions such as signal transduction and immune response. The diffusion of molecules in the heterogeneous field is thought to affect the process of searching for interaction targets to perform their functions. Here, we perform mesoscale simulations to investigate the diffusivities of molecules in different heterogeneous fields. The effects of the heterogeneity in the fields, molecular interactions, concentration, and field preference, on the diffusivities of particles were analyzed. We find that the differences in diffusivities were produced according to the difference in diffusion coefficients between the two phases and the distribution of residence times in the two phases. Increasing the particle concentration or strengthening the intermolecular interaction increase the aggregation of the diffusing particles, resulting in a decrease in their diffusivity. Moreover, the diffusivities depend on the type of barrier, i.e. preference of Lo or Ld domains.