Redox property of water-oxydizing catalyst Mn cluster in photosynthesis

2015 Fiscal Year Final Research Report

• Project/Area Number: 25410009
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Physical chemistry
• Research Institution: Nagoya University
• Principal Investigator: Kato Yuki 名古屋大学, 理学(系)研究科(研究院), 助教 (10376634)
• Co-Investigator(Renkei-kenkyūsha): NOGUCHI Takumi 名古屋大学, 大学院理学研究科, 教授 (60241246)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 光合成 / 水分解 / 酸素発生 / 電子伝達 / 光化学系 / 酸化還元電位 / 分光電気化学

Outline of Final Research Achievements

Photosystem II (PSII) extracts electrons from water at a Mn4CaO5 cluster using light energy and then transfers them to two plastoquinones, the primary quinone electron acceptor QA and the secondary quinone QB. This forward electron transfer is an essential process in light energy conversion. Meanwhile, backward electron transfer is also significant in photoprotection. Modulation of the redox potential (Em) gap of QA and QB mainly regulates the forward and backward electron transfers in PSII. However, the full scheme of electron transfer regulation remains unresolved due to the unknown Em value of QB. In this work, the Em value of QB reduction was measured directly using spectroelectrochemistry in combination with light-induced Fourier transform infrared difference spectroscopy. The result explains the mechanism of PSII photoprotection with an impaired Mn4CaO5 cluster, in which a large decrease in the Em gap between QA and QB promotes rapid charge recombination via QA-.

Free Research Field

生物物理化学