Lipid chain dynamics in diacylglycerol-phosphatidylcholine mixtures studied by slow-motional simulations of spin label ESR spectra

Abstract

Simulation of the ESR spectra from spin-labelled phosphatidylcholine and from spin-labelled diacylglycerol has been used to study the lipid chain dynamics in mixtures of dimyristoyl glycerol with dimyristoyl phosphatidylcholine, as a function of temperature and composition. Successful simulation of the ESR spectra required taking into account slow motional components which was done by using the very anisotropic reorientation model. Chain rotational rates varied with temperature, but not greatly with composition and chain position, which primarily affected chain order. The latter decreased progressively with increasing diacylglycerol content from the lamellar, to inverted hexagonal, to isotropic phase and was consistently lower for the diacylglycerol component than for the phosphatidylcholine component. The order profile of the spin-labelled chains was obtained for both the phosphatidylcholine and diacylglycerol components in a 58:42 mol/mol mixture in the fluid lamellar phase.