Raft Formation in Biological Membranes: A Molecular Dynamics Simulation Study

摘要

Rafts are nanoscale domains in membranes rich with sphingomyelin and cholesterol. The process of raft formation was studied using molecular dynamics simulation method. The model membranes contained three types of lipids: cholesterol (CHOL), D-erythro-n-palmitoyl sphingomyelin (SM), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC). One of the model systems had an SM- and CHOL-enriched domain. It was shown that in this case raft domain spontaneously became thicker and passed from phase L_d to phase L_o. In another model system-a cubic box with mixed SM, CHOL, and POPC-a raft-free bilayer structure in L_o phase was formed. In the third system that had the same lipids mixed in the bilayer structure, a spontaneous formation of the raft was observed. The raft area was 72 nm~2 and the content of CHOL and SM in the raft was 2.4- and 3-fold higher respectively than in the non-raft membrane.