Study on optical storage characters of bacteriorhodopsin molecule film

The photochromic retinal protein bacteriorhodopsin (BR) is found in the cell membrane of Halobacterium salinarium. It is the key protein for photosynthetic growth of H. salinarium. BR shows an exceptional stability towards chemical, thermal, and photochemical degradation. The photochromic properties of Bacteriorhodopsin provide the possibility of application in optical information storage. Photoexcition of the O-state of BR, which has an all-trans confirmation, leads to a state with 9-cis configuration, which is thermally stable. The 9-cis containing photoproduct of the O-state was named P-state. It absorbs at 490nm and can be photochemically reconverted to the initial state. We propose a system of optical information storage in a BR polymer film, which is a reversible optical data recording material and can be rewritten over 10⁶ times without degradation of the film. A three-wavelength EDRAW (Erase Direct Read After Write) experiment was performed. The photoexcited P(490) state shows a permanent storage property confirmed by our contrast ratio experiments. The result of long-term information stroage in BR films more than 1 years is obtained.