Measurements on the pH dependence of metarhodopsin reactions in sonicated rod outer segments.

The kinetics of rhodopsin photolysis in sonicated suspensions of rod outer segments (R O S), unsonicated ROS suspensions and rhodopsin detergent solutions were compared. No significant kinetic differences were detected; however, the energy of activation for the metarhodopsin I to metarhodopsin II reaction was somewhat higher in sonicated ROS suspensions than in the un­ sonicated suspensions. W hile the sonicated preparations contained glycerol, it was not possible to show a chemical influence of glycerol on the reactions of the rhodopsin decay. An often assumed effect that the ROS outer membrane acts as a barrier toward diffusion of protons could not be confirmed.