Photochemical intermediate of third rhodopsin-like pigment in Halobacterium halobium by simultaneous illumination with red and blue light.

We found new photochemical intermediate of third rhodopsin-like pigment (tR) or slow cycling rhodopsin-like pigment (sR) in Halobacterium halobium, which was produced by simultaneous illumination with red and blue light. This illumination is employed for measurements of negative phototaxis. The formation of this intermediate is fast. (With the instrument used, it could not be measured.) The half-time of its decay is ca 150 msec in 4 M NaCl, pH 7.0 at 20 degrees C. The maximum of absorbance is located at 510-530 nm.