Thermal equilibration between the M and N intermediates in the photocycle of bacteriorhodopsin.
The stages in the photocycle of bacteriorhodopsin (BR) involving the M and N intermediates are investigated using a double pulse excitation method. A first (cycling) pulse at 532 nm is followed, with an appropriate time delay, by a second pulse (337, 406, 446, or 470 nm) which induces the M-->BR back-photoreaction. After depletion by the second pulse a repopulation of M in the millisecond range is observed which is interpreted in terms of a thermal N-->M relaxation. It is thus concluded that a (thermal) M<-->N equilibrium accounts for the biphasic decay of M in the BR photocycle. Other models for this stage of the light-driven proton-pump are therefore unnecessary.
Druckmann
S
S
Department of Physical Chemistry, Hebrew University of Jerusalem, Israel.
Heyn
M P
MP
Lanyi
J K
JK
Ottolenghi
M
M
Zimanyi
L
L
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000528:radiation effects*; D055592:Biophysical Phenomena; D001703:Biophysics; D019617:Halobacterium salinarum / Q000737:chemistry / Q000528:radiation effects; D008027:Light; D008956:Models, Chemical; D010777:Photochemistry; D013816:Thermodynamics
D001436:Bacteriorhodopsins