Femtosecond fluorescence upconversion studies of light harvesting by β-carotene in oxygenic photosynthetic core proteins
Femtosecond fluorescence upconversion studies of light harvesting by β-carotene in oxygenic photosynthetic core proteins
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DOI：
10.1021/jp046893p
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发表时间：
2004-12-09
影响因子：
3.3
通讯作者：
Fleming, GR
中科院分区：
文献类型：
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作者：
Holt, NE;Kennis, JTM;Fleming, GR
利用飞秒荧光上转换技术研究了光系统（PS） I核心复合物和PSII的CP43、CP47和反应中心（RC）蛋白中β -胡萝卜素向叶绿素的能量传递。类胡萝卜素的S-2寿命/转移效率与溶液中的β -胡萝卜素相比，分别为97 fs/33% （CP43）、100 fs/31% （CP47）、106 fs/26% （PSII-RC）和62 fs/57% （PSI）。通过将之前的稳态荧光激发测量结果与我们对类胡萝卜素S-2寿命和叶绿素上升动力学的超快结果相结合，我们得出结论，β -胡萝卜素S-1状态对PSII核心蛋白的光收获不显著。在本研究中，PSI在77 K下的稳态荧光激发光谱测量结果显示，β -胡萝卜素到叶绿素的能量转移效率为62 +/- 3%，表明主要转移来自类胡萝卜素S-2状态。有趣的是，虽然PSI和PSII几乎完全利用类胡萝卜素S-2状态进行光收集，但我们发现PSI的这种途径的效率几乎是其两倍。
Energy transfer from beta-carotene to chlorophyll in the photosystem (PS) I core complex and the CP43, CP47, and reaction center (RC) proteins of PSII was studied by the femtosecond fluorescence upconversion technique. The carotenoid S-2 lifetimes/transfer efficiencies, the latter obtained by comparison with beta-carotene in solution, are similar to97 fs/33% (CP43), similar to100 fs/31% (CP47), similar to106 fs/26% (PSII-RC), and similar to62 fs/57% (PSI). By combining previous steady-state fluorescence excitation measurements with our ultrafast results on the carotenoid S-2 lifetime and chlorophyll rise kinetics, we conclude that the beta-carotene S-1 state is insignificant for light harvesting in the PSII core proteins. Measurement of the steady-state fluorescence excitation spectrum of PSI at 77 K in this work yielded a beta-carotene to chlorophyll energy transfer efficiency of 62 +/- 3%, suggesting dominant transfer from the carotenoid S-2 state. Interestingly, while both PSI and PSII almost exclusively utilize the carotenoid S-2 state for light harvesting, we find that this pathway is nearly two times more efficient in PSI.