The objectives of this project are to: (1) investigate the interaction of alcohol with proteins and lipids in biological membranes; (2) study structure and dynamics of membranes composed of lipids with polyunsaturated fatty acids such as docosahexaenoic acid (DHA, 22:6n3); and (3) study lipid-protein interaction related to alcoholism and lipid polyunsaturation. Our goal is to identify general biophysical properties which are important for the functions of biological membranes. (1) The effects of ethanol on lipid bilayers containing fatty acids with varying degree of unsaturation, cholesterol, gangliosides, and sphingomyelin were investigated. Ethanol increases the phase transition temperatures of PE/PC mixtures into non-lamellar phases which is in concordance with a location of ethanol at the lipid-water interface. The decrease of chain order was greater for saturated and monounsaturated hydrocarbon chains than for polyunsaturated ones. The presence of 10 mol% brain gangliosides and cholesterol concentrations below 22 mol% enhanced the disordering effect while cholesterol concentrations higher than 30 mol% reduced it. The impact of the ceramide moiety on ethanol induced changes of chain order was negligible. (2) Lipid-lipid interaction. The temperature dependence of the chain order parameter profile for a series of phosphatidylcholines (PC) with perdeuterated stearic acid, (18:0), in position sn-1 and 18:1n9, 18:2n6, 18:3n3, 20:4n6, 20:5n3, or 22:6n3 in position sn-2 incorporated into a DOPE matrix at a molar ratio of 1:5 was investigated. In the lamellar phase the PC sn-1 chain is appreciably more ordered than in a pure PC multilayer. The increase in order corresponds to an increase of the hydrophobic bilayer thickness of the order of 1 A. Distearoyl-phosphatidyl-choline in the DOPE matrix has a significantly higher order than the unsaturated PCs. Unsaturation decreases order with maximal effect around two-thirds along the chain towards the center of the bilayer. (3) In preparation for a study of lipid protein interaction we investigated the structure of PC bilayers adsorbed to a planar silicon surface from aqueous solution by specular reflection of neutrons and by Atomic Force Microscopy. The lipid adsorbs to the silicon surface as a continuous layer interrupted by irregularly shaped uncovered areas which are 100 to 500 A in size. Neutron reflectometry detects the Angstrom-scale thickness changes of the lipid bilayer as a function of the phase state of the lipid and of the hydrocarbon chain length.