title: Studies on the mechanism of Tris-induced inactivation of oxygen evolution.
abstract: A study was made of the inactivation by Tris of O2 evolution in chloroplasts and the subsequent reactivation of O2 evolution. We conclude: 1. At concentrations of Tris sufficient to inhibit O2 evolution directly, a slow rate (t 1/2 approximately 20--25 min) of inactivation occurs; 2. Inactivation is accelerated (t 1/2 approximately 2 min) by weak light absorbed by system II and is rate limited by a dark step with a half-time of about 200 s; 3. Minimally one quantum event within System II is sufficient to inactive 50--70% of the O2 evolving centers; 4. This process is 3-(3,4-dichlorophenyl)-1,1-dimethylurea insensitive but is inhibited by reduced dichlorophenol indophenol and phenazine methosulfate, carbonylcyanide-p-trifluoromethoxyphenylhydrazone, 2-(3-chloro-4-trifluoromethyl)-anilino-3,5-dinitrothiophene and tetraphenylboron; 5. Partial reactivation of inactive O2 evolving centers is affected by the use of the same reagents inhibiting the light induced inactivations; 6. The life-time (t 1/2 approximately 1 to 3 h) of the activable state is correlated with diffusion across thylakoids of the larger manganese pool released from binding sites and remaining in thylakoids following inactivation of O2 evolution.
mesh_terms: D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002736:Chloroplasts / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D004237:Diuron / Q000494:pharmacology; D008027:Light; D008345:Manganese / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects*; D014325:Tromethamine / Q000494:pharmacology*
chemical_list: D014325:Tromethamine; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D008345:Manganese; D004237:Diuron; D010100:Oxygen