A time-resolved spectral study of the K and KL intermediates of bacteriorhodopsin.
Nanosecond time-resolved absorption measurements on the photolysis products of bacteriorhodopsin (BR) in intact membranes are reported. At room temperature in fluid solution a single intermediate (KL) is seen 10 ns after excitation. Both spectral and kinetic results are consistent with the KL intermediate converting to the L intermediate by a single first order reaction. The observed temperature-dependent rate has the Arrhenius parameters: Ea = 10.5 kcal/mol, A = 5 x 10(13) s-1. The precursor to the KL intermediate is also observed. Its spectral character is consistent with the K intermediate which has been previously reported. The current data is consistent with a linear sequence in the BR photocycle for K, KL, and L in room temperature fluid solution. Differences in the spectral characteristics of the K intermediates described here and elsewhere are discussed in terms of differences in the microenvironment around the retinal moiety and the affect this may have on the conformation of the chromophore.
Milder
S J
SJ
Department of Chemistry, University of California, Santa Cruz 95064.
Kliger
D S
DS
D001436:Bacteriorhodopsins; D006217:Halobacterium; D066298:In Vitro Techniques; D007700:Kinetics; D010777:Photochemistry; D013057:Spectrum Analysis
D001436:Bacteriorhodopsins