The photoinduced changes of absorbance as well as proton release and u
ptake have been observed for an azulenic analog of wild-type bacterior
hodopsin. The release and uptake of protons have been measured using a
highly sensitive electrochemical technique. Bacteriorhodopsin membran
e patches on a tin-oxide electrode produce a transient photocurrent th
at is negative for proton release and positive for proton uptake. For
azulenic bacteriorhodopsin the photocurrent is approximately 20% of th
e transient observed with native bacteriorhodopsin. The existence of t
he photoinduced absorbance changes and the transient photocurrent are
important results for gaining further insight into the photoinduced fu
nction of bacteriorhodopsin.