Bacteriorhodopsin "detergent-monomers," blue shift and velocity of light-dark adaptation.

Bacteriorhodopsin was incubated in various detergent solutions. Absorbance, circular dichroism and size of fragments obtained were investigated. Among all the detergents used, only Triton-X-100 and Nonidet P 40 led to monomers of bacteriorhodopsin. The blue shift of the absorbance maximum of the dark-adapted form and the slow down of dark adaptation are the sole parameters affected by the disruption of the trimeric organization of bacteriorhodopsin. Other spectral characteristics, such as reduction of amplitude of light adaptation, are affected by the presence of detergents independently of the associated or dispersed state of the pigment.