Biophys. J. 81, 204 (2001)
Center for Molecular Modeling, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323 USA
The structure of a fully hydrated mixed
(saturated/polyunsaturated) chain lipid bilayer in the biologically
relevant liquid crystalline phase has been examined by performing a
molecular dynamics study. The model membrane, a
1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (SDPC, 18:0/22:6 PC) lipid bilayer, was investigated at constant (room)
temperature and (ambient) pressure, and the results obtained in the
nanosecond time scale reproduced quite well the available experimental
data. Polyunsaturated fatty acids are found in high concentrations in
neuronal and retinal tissues and are essential for the development of
human brain function. The docosahexaenoic fatty acid, in particular, is
fundamental for the proper function of the visual receptor rhodopsin.
The lipid bilayer order has been investigated through the orientational
order parameters. The water-lipid interface has been explored
thoroughly in terms of its dimensions and the organization of the
different components. Several types of interactions occurring in the
system have been analyzed, specifically, the water-hydrocarbon chain,
lipid-lipid and lipid-water interactions. The distribution of dihedral
angles along the chains and the molecular conformations of the
polyunsaturated chain of the lipids have also been studied. Special
attention has been focused on the microscopic (molecular) origin of the effects of polyunsaturations on the different physical properties of membranes.