Deuteration effects on the electrical signals of bacteriorhodopsin mutants D85N, D212N and D96N

Electric and optical absorption kinetic measurements were performed comparatively in water and deuterium oxide for oriented purple membrane samples of bacteriorhodopsin mutants D85N, D212N and D96N embedded in polyacrylamide gel. The signals were analyzed on the basis of the sequential model with reversible reactions for the photo-cycle. From the rate constants of the reactions, obtained by analyzing the optical absorption signals, the electrogenicities of the intermediates were calculated. In all the cases, isotope effects were found, which gave the possibility to draw some conclusions concerning the role of water in proton pumping and the dynamics of charge motions in the course of the photo-cycle. (author) 5 figs., 1 tab., 39 refs