Neutron Diffraction Studies on Incorporation of Hexane into Oriented Lipid Bilayers
The generally accepted architectural scheme for biological membranes is the fluid mosaic model (1), in which integral proteins are dispersed singly or as aggregates in a quasi-two-dimensional lipid bilayer matrix. Such molecules, which are strongly partitioned into the bilayer interior, must form mixtures of some type with the alkyl chains. It thus seems reasonable to view the membrane as a quasi-two-dimensional solution of lipids and proteins (2,3). If the bilayer can be understood as a solvent system, it should be possible to define a physicochemical framework within which interactions in biological membranes can be better described. The characterization of natural biological membranes in terms of the interactions of their component parts is a complex problem because of the multiplicity of different kinds of lipids and proteins involved. Thus, as a first step toward the attainment of this goal, we have chosen to study a simpler system consisting of a single solute, hexane, dissolved in a single-component, dioleyl lecithin, bilayer. In addition, we chose to observe the effects of varying water activity on the bilayer structure. Three things we wish to determine from our neutron diffraction studies of this system are (a) the distribution with respect to thickness of hexane and water in the bilayer, (b) the structural modifications of the bilayer induced by the varying hexane and water activities, and (c) the spatial constraints of packing the alkane and water into the bilayer system.
KeywordsAcyl Chain High Relative Humidity Bilayer Structure Absolute Scale Neutron Diffraction Study
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