화학공학소재연구정보센터
Biochemical and Biophysical Research Communications, Vol.503, No.1, 222-227, 2018
Electrogenic reactions in Mn-depleted photosystem II core particles in the presence of synthetic binuclear Mn complexes
An electrometrical technique was used to investigate electron transfer between synthetic binuclear manganese (Mn) complexes, designated M - 2 and M - 3, and the redox-active neutral tyrosine radical (Y-Z(center dot)) in proteoliposomes containing Mn-depleted photosystem II (PS II) core particles in response to single laser flashes. In the absence of Mn-containing compounds, the observed flash-induced membrane potential (Delta Psi) decay was mainly due to charge recombination between the reduced primary quinone acceptor Q(A)(-) and the oxidized Y-Z(center dot). More significant slowing down of the Delta Psi decay in the presence of lower concentrations of M - 2 and M - 3 associated with electron donation from Mn in the Mn-binding site to Y-Z(center dot) indicates that these synthetic compounds are more effective electron donors than MnCl2. The exponential fitting of the kinetics of additional electrogenic components of Delta Psi rise in the presence of Mn-containing compounds revealed the following relative amplitudes (A) and lifetimes (tau): for MnCl2-A similar to 3.5, tau-150 mu s, for M - 2 - A similar to 5%, tau-1.4 ms, and for M - 3 - A similar to 5.5%, tau-150 mu s. This suggests that the efficiency of the manganese complexes in electron donation depends on the chemical nature of ligands. The experiments with EDTA-treated samples indicated that the ligands for M - 2 and M - 3 are required for their tight binding with the PS II reaction center. The obtained results demonstrate the importance of understanding the molecular mechanism(s) of flash-induced electrogenic reduction of the tyrosine radical Y-Z(center dot) by synthetic Mn complexes capable of splitting water into oxygen and reducing equivalents. (C) 2018 Elsevier Inc. All rights reserved.