TY - JOUR T1 - On the molecular origin of the protein catalysis of the primary process in bacteriorhodopsin photosynthesis: Retinal photoisomerization JF - Pure and Applied Chemistry Y1 - 1997 A1 - El-Sayed, Mostafa A A1 - Logunov, Stephan L. AB - Using subpicosecond transient optical absorption spectroscopic techniques, the photoisomerization rates and quantum yields were determined for. bacteriorhodopsin, its relevant mutants, its dionized form and at different pH and Cl- concentrations. It is found that the rate is catalyzed and made highly specific around the C-13-C-14 bond by the presence of negative charges within the retinal cavity (e.g., Asp85 and Asp 212). Any perturbation that genetically removes, acid neutralizes, or changes the geometry of these negative charges is found to decrease the tate of photoisomerization, but does not greatly change its quantum yield. These results sue discussed in terms of the changes in the electronic structure of the retinal as well as in the anisotropic charge distribution within the cavity that result from the photoexcitation process. The different potential energy surfaces proposed to explain the dynamics of the photoisomerization process are examined in terms of our observed results. VL - 69 SN - 0033-4545 N1 - Times Cited: 816th IUPAC Symposium on PhotochemistryJul 21-26, 1996Helsinki, finlandIupac M3 - 10.1351/pac199769040749 ER -