Abstract

Bacteriorhosopsin (bR) is a photdynamic protein complex found in the purple membrane of the Halobacterium halobium. In the halobacterial cell it acts as a light driven pump. The bR molecule consists of a single polypeptide chain of 248 amino acids. A retinal molecule linked via a protonated Schiff base to lysine 216 forms the chromophoric group. The proton pumping activity of light adapted bR is associated with conformational changes of the bR molecule during the photocycle. The initial B state of bR has an absorption peak at 570 nm while the long lived M state has an absorption peak at 412 nm. As the initial state has a broad absorption band it can be excited by means of red, yellow or green light. The M state can revert to the initial state via a thermal process or by a photochemical process by excitation with blue light. The lifetime of the M state depends on the reprotonation process which can be altered by chemical and bioengineering methods. The biopolymer might be an alternative to conventional materials for future applications in information technologies.

© 1996 Optical Society of America