Dynamic clustering of lipids in hydrated two-component membranes: results of computer modeling and putative biological impact

Abstract

Delineation and analysis of lateral clustering of lipids in model bilayers is an important step toward understanding of the physical processes underlying formation of lipid domains and rafts in cell membranes. Computer modeling methods represent a powerful tool to address the problem since they can detect clusters of only few lipid molecules – this issue still resists easy characterization with modern experimental techniques. In this work, we propose a computational method to detect and analyze parts of membrane with different packing densities and hydrogen bonding patterns. A series of one- and two-component fluid systems containing lipids with the same polar heads and different acyl chains, dioleoylphosphatidylcholine (18:1) and dipalmitoylphosphatidylcholine (16:0), or with same acyl chains and different polar heads, dioleoylphosphatidylserine (18:1) and dioleoylphosphatidylcholine (18:1), were studied via molecular dynamics simulations. Four criteria of clustering were considered. It was shown that the water–lipid interface of biomembranes represents a highly dynamic and “mosaic” picture, whose parameters depend on the bilayer composition. Some systems (e.g. with 20–30% of the anionic lipid) demonstrate unusual clustering properties and demand further investigation at molecular level. Lateral microheterogeneities in fluid lipid bilayers seem to be among the most important factors determining the nature of the membrane–water interface in a cell.

Keywords:

• cluster analysis
• computer similations
• hydrated lipid bilayer
• lateral heterogeneity of lipids
• molecular dynamics

Acknowledgments

This work was supported by the Ministry of Education and Science of the Russian Federation, by the Russian Foundation for Basic Research, and by the RAS Programe “Basic fundamental research for nanotechnologies and nanomaterials.” Access to computational facilities of the Joint Supercomputer Center RAS (Moscow), Computer Center of South Ural State University, and Moscow Institute of Physics and Technology is gratefully acknowledged. We thank Natalia Kuznetsova for editing this article.