Picosecond Conformational Intermediates in The Bacteriorhodopsin Photocycle.

Abstract

The purple membrane of Halobacterium halobrium contains the protein bacteriorhodopsin (BR) which undergoes a cyclic reaction involving changes in the conformation and structure of the retinal chromophore. The value of BR as a model for the molecular dynamics associated with the retinal chromophore in visual pigments and for the associated proton and ion pumping is well established [1-2]. Although many aspects of both the BR dynamics and the structure of BR intermediates have been reported [2], significant parts of the molecular mechanism underlying its biochemical function remain either unknown or only partially characterized. The initial molecular changes occuring during the first few picoseconds after excitation are of particular interest since they involve the molecular mechanisms by which chemical energy is stored to drive the biochemical activity.