期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
卷 1857, 期 6, 页码 848-859出版社
ELSEVIER
DOI: 10.1016/j.bbabio.2016.03.013
关键词
Photosynthesis; Photosystem 2 (PSII); Oxygen (O-2) evolution; Water oxidation; Kok model; Flash induced oxygen evolution pattern (FIOP)
资金
- Swedish Research Council [2009-33,450-66,982-67]
- Swedish Energy Agency [36,648-1]
- K&A Wallenberg Foundation (Artificial Leaf Project) [KAW 2011.0055]
- Umea University (Solar Fuels Strong Research Environment)
The oxygen-evolving complex (OEC) in photosystem II catalyzes the oxidation of water to molecular oxygen. Four decades ago, measurements of flash-induced oxygen evolution have shown that the OEC steps through oxidation states S-0, S-1, S-2, S-3 and S-4 before O-2 is released and the S-0 state is reformed. The light-induced transitions between these states involve misses and double hits. While it is widely accepted that the miss parameter is S state dependent and may be further modulated by the oxidation state of the acceptor side, the traditional way of analyzing each flash-induced oxygen evolution pattern (FIOP) individually did not allow using enough free parameters to thoroughly test this proposal. Furthermore, this approach does not allow assessing whether the presently known recombination processes in photosystem II fully explain all measured oxygen yields during Si state lifetime measurements. Here we present a global fit program that simultaneously fits all flash-induced oxygen yields of a standard FIOP (2 Hz flash frequency) and of 11-18 FIOPs each obtained while probing the S-0, S-2 and S-3 state lifetimes in spinach thylakoids at neutral pH. This comprehensive data treatment demonstrates the presence of a very slow phase of S-2 decay, in addition to the commonly discussed fast and slow reduction of S-2 by Y-D and Q(B)(-), respectively. Our data support previous suggestions that the S-0 -> S-1 and S-1 -> S-2 transitions involve low or no misses, while high misses occur in the S-2 -> S-3 or S-3 -> S-0 transitions. (C) 2016 Elsevier B.V. All rights reserved.
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