molecular face of lipid rafts in model membranes

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 45; pp. 17367 - 17372
• Main Authors: Risselada, H. Jelger, Marrink, Siewert J
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 11-11-2008; National Acad Sciences
• Subjects: Biological Sciences; Cell membranes; Cells; Chemical composition; Cholesterol - chemistry; Cholesterols; Computer Simulation; Interfacial tension; Lipids; Membrane Microdomains - chemistry; Membrane Microdomains - ultrastructure; Membranes; Modeling; Models, Molecular; Molecular dynamics; Molecules; Rafts; Simulation; Simulations
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0807527105

Cell membranes contain a large number of different lipid species. Such a multicomponent mixture exhibits a complex phase behavior with regions of structural and compositional heterogeneity. Especially domains formed in ternary mixtures, composed of saturated and unsaturated lipids together with cholesterol, have received a lot of attention as they may resemble raft formation in real cells. Here we apply a simulation model to assess the molecular nature of these domains at the nanoscale, information that has thus far eluded experimental determination. We are able to show the spontaneous separation of a saturated phosphatidylcholine (PC)/unsaturated PC/cholesterol mixture into a liquid-ordered and a liquid-disordered phase with structural and dynamic properties closely matching experimental data. The near-atomic resolution of the simulations reveals remarkable features of both domains and the boundary domain interface. Furthermore, we predict the existence of a small surface tension between the monolayer leaflets that drives registration of the domains. At the level of molecular detail, raft-like lipid mixtures show a surprising face with possible implications for many cell membrane processes.