title: Thermal equilibration between the M and N intermediates in the photocycle of bacteriorhodopsin.
abstract: 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.
authors.affiliation: Department of Physical Chemistry, Hebrew University of Jerusalem, Israel.
authors.forename: S
authors.initials: S
authors.lastname: Druckmann
authors.forename: M P
authors.initials: MP
authors.lastname: Heyn
authors.forename: J K
authors.initials: JK
authors.lastname: Lanyi
authors.forename: M
authors.initials: M
authors.lastname: Ottolenghi
authors.forename: L
authors.initials: L
authors.lastname: Zimanyi
mesh_terms: 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
chemical_list: D001436:Bacteriorhodopsins