9,13-dicis-rhodopsin and its one-photon-one-double-bond isomerization

Incubation of purified 9,13-dicis-retinal with cattle opsin in 2% digitonin at 20 degrees C produced two pigments, one unstable (lambda max 478 nm) and the other stable (lambda max 485 nm) in hydroxylamine. The two pigments exhibited different characteristics. HPLC analysis revealed that the chromophores of these pigments have respectively 9,13-dicis and 9-cis geometries. Under various conditions the amount of 9,13-dicis-rhodopsin formed never exceeded 30% of the total pigments. The addition of 9,13-dicis-retinal to the ROS suspension containing opsin produced 9-cis-rhodopsin in 97% yield. Irradiation of the 9,13-dicis-rhodopsin mainly produced 13-cis-retinal, while 9-cis-rhodopsin produced the all-trans isomer. These results demonstrated that the one-photon-one-double-bond isomerization process took place in 9,13-dicis-rhodopsin.