Peculiarities of rhodopsin photoconversion at the early stages of photolysis

The primary stages of rhodopsin photolysis were studied with the low temperature absorption spectroscopy technique. Digitonin extract of bovine rhodopsin was irradiated at -155 degrees C with blue light (436 nm). The following changes of the dark spectrum were recorded in the course of slow rise of the temperature in 1-3 degrees C steps. Simultaneous appearance of more than one spectral product was revealed throughout the batho- to lumirhodopsin transition. An intermediate product transformed along with bathorhodopsin to a next product known as a "blue-shifted intermediate", was observed. The data suggest that appearance of more than one intermediate at each stage of the rhodopsin photolysis reflects existence of multiple conformation states of the rhodopsin molecule in the course of its photoconversion.