Abstract

Bacteriorhodopsin (bR) is a photosensitive molecule found in the cell membrane of Halobacterium halobium. It has a large extinction coefficient of 6.3 x 10⁴ M^-1 cm^-1 at 568 nm. A chromophore, which is responsible for absorption, undergoes rapid isomerization upon photon absorption. In tens of µs, the M photo-intermediate whose absorption maximum is at 412 nm forms. Irradiation of the M photointermediate results in regeneration of the original B state. Thus, bR has a potential as a photoreversible photochromic material. It is characterized by a high quantum efficiency of over 60%, exceptional cyclical durability of more than million cycles, and excellent mechanical stability over several years.

© 1995 Optical Society of America