PHOTORESPONSE OF BACTERIORHODOPSIN IMMOBILIZED IN POLYACRYLAMIDE-GEL MEMBRANES

A two-chambered cell has been designed and constructed for the measure ment of photoresponses of bacteriorhodopsin immobilized in polyacrylam ide gel (FAG) membranes. The photoresponse of bacteriorhodopsin was de termined by measuring the pH variation in each chamber independently, for long periods of illumination. The aim was to verify the light driv en proton transfer of bacteriorhodopsin immobilized in FAG membranes. However, the same pH variation was observed in the two chambers irresp ective of whether oriented or nonoriented bacteriorhodopsin immobilize d in FAG membranes were employed. It has been concluded that upon illu mination of the biosynthetic membrane, protons were not transfered fro m one chamber into another. The pH variation was then attributed to th e association and dissociation of protons from bacteriorhodopsin in th e membrane. The protonation and deprotonation of FAG interfered with t he photoresponse of bacteriorhodopsin due to pH disturbance, even thou gh light had no direct effect on FAG. This might be the main reason fo r the very low efficiencies obtained in such energy transducing biosyn thetic membranes.