Lanmuir-Blodgett (LB) films were prepared from a bacteriorhodopsin (bR) protein. The bR film was formed on the water surface by a self organizing process of soya-PC molecules as a bilayer around the protein. When the film was pressed on the water surface a bR Langmuir film was formed with the negatively charged end of the molecules directed towards the water, surrounded by lipid molecules forming a bilayer, at the nearest proximity, and a monolayer, at larger distances. When the films were deposited on a solid substrate by an upwards or downwards movement the dipoles of the bR molecules were oriented in opposites directions. The kinetics of charge motions, and the optical signals of the M state in the bR photocycle were almost identical when measured using dry samples or at low humidity. The rate of formation of the M state of the bR photocycle was found to be independent of moisture, but the decay of the M state changed from mono- to double-exponential when the medium was changed from water to a water vapour atmosphere, and the decay time of the new component increased to a few seconds. Finally, it was observed that in dry films the M state kinetics corresponded to the optical recovery of the light adapted from of bR. The kinetical information obtained from the dry films confirms the existence of two distinct M intermediates as parallel or sequential states in modified photocycle in dry bR LB films. The electrical signals of the films deposited in opposite directions had opposite signs and their amplitudes were proportional to the numbers of the monolayers deposited.
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