期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
卷 1767, 期 3, 页码 197-203出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2007.02.001
关键词
EPR; ESR; ENDOR; Mn-cluster; oxygen evolution; photosystem II
Protons in the vicinity of the oxygen-evolving manganese cluster in photosystem 11 were studied by proton matrix ENDOR. Six pairs of proton ENDOR signals were detected in both the S-0 and S-2 states of the Mn-cluster. Two pairs of signals that show hyperfine constants of 2.3/2.2 and 4.0 MHz, respectively, disappeared after D2O incubation in both states. The signals with 2.3/2.2 MHz hyperfine constants in S-0 and S-2 state multiline disappeared after 3 h of D2O incubation in the S-0 and S-1 states, respectively. The signal with 4.0 MHz hyperfine constants in So state multiline disappeared after 3 h of D2O incubation in the S-0 state, while the similar signal in S-2 state multiline disappeared only after 24 h of D2O incubation in the S-1 state. The different proton exchange rates seem to be ascribable to the change in affinities of water molecules to the variation in oxidation state of the Mn cluster during the water oxidation cycle. Based on the point dipole approximation, the distances between the center of electronic spin of the Mn cluster and the exchangeable protons were estimated to be 3.3/3.2 and 2.7 angstrom, respectively. These short distances suggest the protons belong to the water molecules ligated to the manganese cluster. We propose a model for the binding of water to the manganese cluster based on these results. (c) 2007 Elsevier B.V. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据