Absorption spectrum of cattle hypsorhodopsin

Abstract

On irradiation at liquid helium temperatures, rhodopsin is converted into hypsorhodopsin which decays to bathorhodopsin above 23 K. The absorption spectrum of cattle hypsorhodopsin (λ max = 435 nm) is found to include a new sideband around 540 nm. This sideband may be due to π * ← π transition to 1 A − g like state, which is made partially allowed by distortion of polyene chain of the retinylidene chromophore.