Isomerization and Deprotonation During the Photocycle of Deionized and Acid Bacteriorhodopsin by Time Resolved Raman

A time resolved resonance Raman study is performed in the C=C stretching and in the "fingerprint" regions for the acid blue, acid purple and deionized bacteriorhodopsin. The results suggest that the isomerization to form the K 610 and then the L 550 intermediates seem s to occur during the cycle of the low pH and deionized bacteria. These results imply that the removal of the cations, or an increase in the hydrogen ion concentration, prevent only the deprotonation process from occuring. It further shows that isomerization alone is not a prerequisite for the deprotonation process.