Two photocycles in halobacterium halobium that lacks bacteriorhodopsin

The photochemical reactions in bacteriorhodopsin-free mutant (bR^?) of Halobacterium halobium (JW-1) membranes have been studied using flash photolysis. Two photocycles were found in envelope vesicles as well as in a membrane fragment from (JW-1). A pigment absorbing at ca. 590 nm undergoes a faster photocycle, with a phototransient at ca. 500 nm ($\text{τ}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{～- 10 ms}$). A second pigment absorbing at ca. 580 nm undergoes a slower photocycle, accompanying a phototransient absorbing below 410 nm ($\text{τ}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{～- 0.8 s}$).