title: Kinetics of purple membrane dark-adaptation in the presence of Triton X-100.
abstract: The kinetics of purple membrane dark adaptation were studied at pH 5 and 7, in the presence and absence of the nonionic detergent Triton X-100. The effect of both sublytic and lytic surfactant concentrations has been considered. Our results show that: (a) dark adaptation is faster at pH 5 than at pH 7, (b) dark adaptation is slower, and of smaller amplitude, in the presence than in the absence of Triton X-100. The data may be interpreted in terms of a simple first-order kinetic model, according to which light-dark adaptation would depend basically on the equilibrium between the 13-cis- and the all-trans-isomers. The experiments also suggest that at pH 5, but not at pH 7, solubilizing surfactant concentrations produce a considerable increase in the velocity of the dark adaptation reaction, perhaps through changes in the microenvironment of a protonable group.
authors.affiliation: Department of Biochemistry, University of the Basque Country, Bilbao, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: González-Mañas
authors.forename: F M
authors.initials: FM
authors.lastname: Goñi
authors.forename: M
authors.initials: M
authors.lastname: Tribout
authors.forename: S
authors.initials: S
authors.lastname: Paredes
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry*; D003623:Dark Adaptation / Q000187:drug effects*; D003902:Detergents / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology*; D013053:Spectrophotometry
chemical_list: D003902:Detergents; D011092:Polyethylene Glycols; D001436:Bacteriorhodopsins; D017830:Octoxynol