MODELING OF LONG-TERM PHOTORESPONSE OF BACTERIORHODOPSIN IMMOBILIZED ON CELLULOSE-ACETATE MEMBRANES

Purple membrane fragments with its integrated protein bacteriorhodopsi n were immobilized on lipid impregnated and lipid free cellulose aceta te membranes. Two mathematical models were suggested to simulate the p hotoresponse curves of these membranes which were obtained by measurin g the pH variation independently in each chamber of a specifically des igned photoactivity cell for long periods of illumination. The first o rder model suggested was mainly based on the existence of light phase deprotonation and dark phase reprotonation reactions. The overall depr otanation rate constants were found to be slightly less than the overa ll reprotonation rate constants with the first order kinetics. In the second model, the pH change-time data were expressed by a mathematical decay function. There has been found a great agreement between the fi rst order rate constants and the decay constants.