Singlet Energy Dissipation in the Photosystem II Light-Harvesting Complex Does Not Involve Energy Transfer to Carotenoids
Singlet Energy Dissipation in the Photosystem II Light-Harvesting Complex Does Not Involve Energy Transfer to Carotenoids
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DOI：
10.1002/cphc.200900852
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发表时间：
2010-04-26
期刊：
影响因子：
2.9
通讯作者：
Holzwarth, Alfred R.
中科院分区：
文献类型：
--
作者：
Mueller, Marc G.;Lambrev, Petar;Holzwarth, Alfred R.
利用飞秒瞬态吸收技术研究了拟南芥玉米黄质缺失突变体npq1和玉米黄质富集突变体npq2主要光收集复合物II （LHC II）低聚物的能量耗散机制。比较了在不同激发强度下得到的动力学，并讨论了单线态-单线态湮灭的意义。在没有湮灭的条件下，两种类型的LHC II低聚物表现出分布双指数（双峰）动力学，其寿命约为5- 20ps，约为200- 400ps，具有叶绿素激发态典型的瞬态光谱。这些数据可以用仅涉及叶绿素激发态的双态室模型进行动力学描述。有证据表明，与先前的建议不同，类胡萝卜素激活状态和类胡萝卜素自由基状态都不参与猝灭机制。我们认为在LHC II低聚物中形成了叶绿素-叶绿素电荷转移态，这是猝灭过程的中间产物。讨论了体内非光化学猝灭的相关性。
The energy dissipation mechanism in oligomers of the major light-harvesting complex II (LHC II) from Arabidopsis thaliana mutants npq1 and npq2, zeaxanthin-deficient and zeaxanthin-enriched, respectively, has been studied by femtosecond transient absorption. The kinetics obtained at different excitation intensities are compared and the implications of singlet-singlet annihilation are discussed. Under conditions where annihilation is absent, the two types of LHC II oligomers show distributive biexponential (bimodal) kinetics with lifetimes of approximate to 5-20 ps and approximate to 200-400 ps having transient spectra typical for chlorophyll excited states. The data can be described kinetically by a two-state compartment model involving only chlorophyll excited states. Evidence is provided that neither carotenoid excited nor carotenoid radical states are involved in the quenching mechanism at variance with earlier proposals. We propose instead that a chlorophyll-chlorophyll charge-transfer state is formed in LHC II oligomers which is an intermediate in the quenching process. The relevance to non-photochemical quenching in vivo is discussed.