Proton-Coupled Electron Transfer from Tyrosine in a Tyrosine−Ruthenium−tris-Bipyridine Complex: Comparison with TyrosineZ Oxidation in Photosystem II

摘要: The pH- and the temperature dependence of rate constant for electron transfer from tyrosine to ruthenium in Ru(II)(bpy)2(4-Me-4‘CONH-l-tyrosine etyl ester-2,2‘-bpy) 2PF6 was investigated using flash photolysis. At a pH below pKa ≈ 10 increased monotonically with pH. This increase consistent concerted transfer/deprotonation mechanism. Also indicative reaction unusually high reorganization energy, 2 eV, extracted temperature-dependent measurements. Deprotonation group, at > pKa, resulted 100-fold due decreased λ = 0.9 eV. Also, became independent In Mn-depleted photosystem II similar has been found tyrosineZ (TyrZ) oxidized primary donor P680+. On basis kinetic similarities we propose that mechanisms two systems are same, is, transf...