Problems in Membrane Biophysics

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9316256 McConnell This research explores the use of lipid/protein monolayers at the air-water interface to study specific cell membrane-monolayer membrane interactions. Fluorescence microscopy is the principle technique used to carry out these studies. Membrane proteins of special interest are the class II molecules of the major histocompatibility complex (MHC). These proteins are incorporated in lipid monolayers. The interaction between MHC- peptide complexes and peptide specific, MHC restricted T-cell hybridomas is studied by fluorescence microscopic observations of suitably labeled protein/peptide/lipid, taking advantage of recently developed knowledge concerning physical properties of lipid monolayers. Apposition of T-cells to the monolayers is carefully controlled using cell suspension methods. Detection of the binding of specific MHC-peptide complexes in monolayers to a population of T-cells is a potential novel technique leading to the identification of reactive T-cells clones, and to the eventual sequencing of T-cell receptor genes. %%% The surface of the earth is approximately 75% air-water interface. In spite of the potential ecological and environmental significance of this interface, remarkably little is known about physical and chemical events that are interfacial. This is simply because so few molecules are present at this interface at any one time. Research in the laboratory of Harden McConnell at Stanford has brought about a breakthrough in technique for observing chemical, physical and biological events at this interface. This technique has involved the application of fluorescent molecular probes that bind only to the interface--they are not soluble in water, nor do they vaporize into the air. These probes permit the observation of events at the interface using a simple fluorescence optical microscope. Many phenomena (phase transitions, chemical reactions, and bacterial motion) can be observed at the air-water interface by their eff ects on the spatial distribution of these fluorescent molecules. Literally dozens of new observations have been reported in the scientific literature using these techniques. A study currently being initiated in this laboratory concerns the effects of electrical fields on biological cells. ***