THE PHOTOCHROMIC PROPERTIES OF 4-KETO BACTERIORHODOPSIN

The all-trans-retinal of the native chromoprotein of bacteriorhodopsin (BR) purple membrane was replaced with the synthetic 4-keto retinal. Gelatin films were made from the reconstituted BR and the intensity-de pendent basic optical properties were investigated. It is shown that a t room temperature the M-state is composed of two different absorption bands (maximum at 413 nm and 435 nm) with different relaxation times. Unexpected low-intensity transmission properties which cannot be expl ained by the two-level model are reported. The M-state of the 4-keto B R is shown to be about 100 times slower than the M-state of the simila r wild type BR-film.