Mixed lipid-protein films of bacterial photosynthetic reaction centres. II. Mixed multilayers on solid supports

Mixed lipid-protein multilayers composed of the reaction centre (RC) proteins from the Chloroflexus aurantiacus and Rhodobacter sphaeroides (wild type) photosynthetic bacteria and synthetic lipids were investigated. The optimal conditions for forming thin films on solid plates (approximately 100% transfer) were 30 mN/m surface pressure and transfer of the interfacial monolayers from the buffer/air interface onto the plates by the Langmuir-Schaefer method. The films transferred onto quartz and optical transparent current-conducting plates retained their optical and photoelectric properties. The preferential orientation of the protein of the interfacial surface depended on the type of lipid used. In RC-acryloylphosphatidylethanolamine films, the H subunit of the RC from Rhodobacter sphaeroides was oriented toward the water phase, in contrast to RC-diacetylenic acid films, in which the H-subunit was oriented toward the air phase. It is shown that RC can change their orientation in a monolayer, even to the opposite one, depending on the type of lipid matrix.