Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Chemphyschem. 2010 Apr 26;11(6):1289-96. doi: 10.1002/cphc.200900852.
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 approximately 5-20 ps and approximately 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.
通过飞秒瞬态吸收研究了拟南芥突变体 npq1 和 npq2（分别为玉米黄质缺乏和玉米黄质富集）中主要光捕获复合物 II（LHC II）低聚物的能量耗散机制。比较了在不同激发强度下获得的动力学，并讨论了单线态-单线态湮灭的含义。在不存在湮灭的情况下，两种类型的 LHC II 低聚物显示出具有约 5-20 ps 和约 200-400 ps 的寿命的分布双指数（双峰）动力学，具有典型的叶绿素激发态的瞬态光谱。数据可以通过仅涉及叶绿素激发态的两态隔室模型进行动力学描述。有证据表明，与早期的提议相反，在猝灭机制中既不涉及类胡萝卜素激发态也不涉及类胡萝卜素自由基态。相反，我们提出在 LHC II 低聚物中形成叶绿素-叶绿素电荷转移态，这是猝灭过程中的中间态。讨论了其与体内非光化学猝灭的相关性。
