Vibrational Studies of Lipid Structure and Dynamics

Strauss, Herbert

Abstract

Raman spectroscopy has been much used to study the lipid bilayer in model and real biological membranes, and recently infrared spectroscopy has emerged as an equally viable technique. The kinds of information that can be derived from these studies are varied and unique, varied because of the sensitivity of vibrational spectra to factors such as conformation, environment, and mobility, and unique because of the fast time scale associated with the events that give rise to the spectra. The object of this proposal is to provide the needed groundwork for interpreting spectra and to apply this knowledge to the study of specific model systems. We will approach this problem through the study of model hydrocarbon chain systems such as n-alkanes, carboxylic acids, and phospholipids and will build on the results of our earlier work in establishing quantitative relations between vibrational spectra and the structure and dynamics of the lipid bilyer. We will focus on separating static and dynamic effects. Static effects include those of chain conformation, the determination of which as an overall average and at specific sites in the lipid chain will be one of our principal aims. Another principal aim, associated with dynamic effects, will be to evaluate chain mobility through an analysis of C-H stretching band shapes and thus provide a completely new kind of information about the bilayer. A new """"""""average-chain"""""""" approach to analyzing the vibrations of disordered hydrocarbon chains applicable to lipid spectra will be developed. Our ability to identify different types of localized conformational defects in chains will be utilized to establish relations between the phase of the bilayer and the nature of the associated conformational disorder. Application of the techniques for studying chain conformation and mobility will be made to the study of pressure reversal of anesthetic induced disorder in model membrane systems.