Irregularity in Opsin Shifts of Hydroretinochromes

Hydroretinochromes were reconstituted with aporetinochrome and hydroretinal analogues; 7,8-dihydroretinal, 5,6-dihydroretinal, dehydroretinal, and their analogues. The ‘opsin shifts’ were 2200 ± 100 cm−1 for trienals and pentaenals, whereas 1600 ± 100 cm−1 was the value for tetraenals.