title: Chromophore reorientations in the early photolysis intermediates of bacteriorhodopsin.
abstract: The photoselection-induced time-resolved linear dichroism of a bacteriorhodopsin suspension of purple membrane from 350 to 750 nm is measured by a new pseudo-null measurement technique. In combination with time-resolved absorption measurements, these linear dichroism measurements are used to determine the reorientation of the retinal chromophore of bacteriorhodopsin from 50 ns to 50 microseconds after photolysis. This time range covers the times when the K photointermediate decays to form L, as well as the early times during the formation of the M intermediate in the photocycle. An analysis of the photoselection-induced linear dichroism measured directly, along with the absorbance changes polarized parallel to the linearly polarized excitation, shows that the anisotropy is invariant over this time period, implying that the photolyzed chromophore rotates less than 8 degrees C with respect to unphotolyzed chromophores during this part of the photocycle.
authors.affiliation: Department of Chemistry and Biochemistry, University of California at Santa Cruz 95064, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Esquerra
authors.forename: D
authors.initials: D
authors.lastname: Che
authors.forename: D B
authors.initials: DB
authors.lastname: Shapiro
authors.forename: J W
authors.initials: JW
authors.lastname: Lewis
authors.forename: R A
authors.initials: RA
authors.lastname: Bogomolni
authors.forename: J
authors.initials: J
authors.lastname: Fukushima
authors.forename: D S
authors.initials: DS
authors.lastname: Kliger
mesh_terms: D016880:Anisotropy; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000528:radiation effects*; D055592:Biophysical Phenomena; D001703:Biophysics; D019617:Halobacterium salinarum / Q000737:chemistry / Q000528:radiation effects; D008962:Models, Theoretical; D010777:Photochemistry; D010782:Photolysis; D013053:Spectrophotometry / Q000379:methods; D013816:Thermodynamics
chemical_list: D001436:Bacteriorhodopsins