SQUID HYPSORHODOPSIN

Abstract— Squid hypsorhodopsin is produced by irradiating rhodopsin or isorhodopsin with yellow light (>480nm) at liquid He temperature (4K). Compared with cattle rhodopsin, squid rhodopsin easily converts to a photosteady state mixture composed of rhodopsin, isorhodopsin, hypsorhodopsin and bathorhodopsin at this temperature and the amount of hypsorhodopsin in the mixture is high. Hypsorhodopsin has a main absorption peak at 446 nm, and its extinction coefficient is 1.16 times larger than that of rhodopsin. On warming above 35 K, squid hypsorhodopsin converts to bathorhodopsin. A kinetic analysis indicates that the hypsorhodopsin can be formed not only from rhodopsin but also from isorhodopsin. On absorption of light. both squid bathorhodopsin and hypsorhodopsin convert to a mixture of rhodopsin and isorhodopsin.