RETARDATION OF THE PHOTOCYCLE IN BACTERIO RHODOPSIN BY CYCLOHEXANEDIONE

Effects of the modification of the arginine residues in bacteriorhodop sin (BR) by 1,2-cyclohexanedione (CHD) were investigated in the wild t ype (WT) pigment and a single amino acid mutant D96N. As measurements with pyranine, a pH-sensitive dye, showed CHD-modification of BR-WT do es nol prevent the transmembrane proton transfer but slows down the pr oton uptake from the medium. CHD also slows down the reprotonation of the BR Shiff base as seen from the kinetics of absorption changes and photocurrents associated with the decay of WT pigment's M form. Howeve r, CHD does not appear to affect the M decay in the D96N mutant.Spectr al and photopotential measurements indicate that the major result of t he CHD modification, the slowing of the regeneration of the initial BR (M-->BR transition), becomes even more pronounced in dry orderly orie nted PM-films. This can be used to advantage in the fabrication of new BR-based bistable photochromic and photoelectrogenic materials for op tics and microelectronics.