A miniaturized micro-fluorescence film balance for protein-containing lipid monolayers spread from a vesicle suspension.

In order to study protein-lipid monolayers at the air/water interface a miniaturized micro-fluorescence film-balance apparatus has been developed and combined with a modified technique of spreading and separating a monolayer from a vesicle suspension. The spreading method provides non-denaturing conditions for protein-lipids. When applied to protein-lipid vesicles, monolayers with incorporated proteins are obtained, and their thermodynamic parameters may be controlled in a well-defined way by film balance techniques. In the apparatus introduced, a movable microscope allows the observation of micro-fluorescence during the tracking of individual domains at the air/water interface of a fixed Langmuir trough. After the control of parameters such as subphase temperature, surface pressure and lateral molecule distribution, a monolayer may be transferred and immobilized on a planar solid support, making it accessible to optical surface-sensitive measuring methods as well as to electron microscopy and scanning probe techniques.