Structure and Dynamic of Pure Stearic Acid and Stearic Acid/Cholesterol (70:30) Bilayers, dopped with 10-Doxyl-Stearic Acid. Molecular Dynamic Study.

GARAY, ALBERTO S.; RODRIGUES, DANIEL E.

Rosario, Argentina

Congreso; XXXV Reunión Anual de la Sociedad Argentina de Biofísica; 2006

SAB

<!-- @page { size: 8.5in 11in; margin: 0.79in } P { margin-bottom: 0.08in } --> Electronic Paramagnetic Resonance (EPR) is an experimental tool, widely used in the study of biological membranes, at molecular level. In this experiment a modified lipid molecule (10-doxyl-stearic acid, “spin labeled SA”) is inserted into the bilayer. The shape and peaks positions of the EPR spectrum produced by this molecule depend on the type and lipid composition of the bilayer where it is inserted. The researcher usually builds a structural and dynamical “idea” of the bilayer behavior from the analysis of the EPR spectrum. But EPR studies employing spin labelled bilayers has some controversial points. There are some works wich argument that the size of chemical group joined to the lipid carrier (doxyl) is big enough to perturb its environment, so that the “marker” would show in the spectrum its own behavior and not of the bilayer where it is [Cadenhead D.A. (1976)] [Taylor M.G. (1983)]. With this motivation we run Molecular Dynamics (MD) simulations of SA and SA/chol (70:30) at different temperatures (285K, 300K, 315K y 330K), in order to study the behavior of a spin labeled molecule inserted in it. The order parameters (S ) of the SA and the labeled SA (SA*) molecules calculated from the simulations of SA/SA* were significant different, but they showed the same tendency under the effect ot the temperature. Identical results were obtained in the system AE/Chol/AE*. The relationship between C10 order parameters of SA (not labeled) in the SA and SA/Chol system were similar to the C10 order parameters of SA*