title: Ionic strength and pH effects on the rates of reduction of spinach plastocyanin by ascorbate.
abstract: Kinetic studies of the reduction of plastocyanin from spinach chloroplasts by ascorbate were carried out using a stopped flow apparatus. The reduction of spinach plastocyanin by ascorbate followed first-order kinetics in the reductant with a rate constant k = 415 M-1.S-1 [20 degrees C, 0.1 M NaCl, pH 8.0 (10 mM Tris-HCl)]. The second-order rate constants for the reduction of plastocyanin by ascorbate increased dramatically with increasing pH and ionic strength. The cationic micelles of cetyltrimethylammonium bromide also accelerated this electron-transfer reaction. The importance of electrostatic interactions between plastocyanin and ascorbate is discussed in relation to the photosynthetic electron-transport reactions.
mesh_terms: D001205:Ascorbic Acid; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D010970:Plastocyanin / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D010970:Plastocyanin; D001205:Ascorbic Acid