Stark spectroscopy of the light-harvesting complex II in different oligomerisation states.
Stark spectroscopy of the light-harvesting complex II in different oligomerisation states.
复制标题
不同寡聚状态下的光捕获复合物 II 的斯塔克光谱。
DOI：
10.1016/s0005-2728(03)00080-x
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
H. Amerongen
中科院分区：
文献类型：
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作者：
M. A. Palacios;R. Frese;C. Gradinaru;C. Gradinaru;I. V. Stokkum;L. Premvardhan;P. Horton;A. Ruban;A. Ruban;R. Grondelle;H. Amerongen
在77 K下，研究了不同寡聚化态（单体、三聚体和聚集态）下光收集配合物II （LHCII）的电场诱导吸收变化（Stark效应）。所有叶绿素（Chl） a分子在qy吸收区表现出电光性质，其特征是在电子激发下偶极矩| Δ μ→|=0.6±0.06 D/f和极化率Tr（Δα） ~ 55±5 Å3/f2的变化与未结合的单体Chl a相似，这表明在存在强激子相互作用的情况下，激发态不存在强离域。Chl b吸收区的Stark效应显著增大，| Δ μ→|值为2.0±0.2 D/f，这是由于与新黄质分子的强相互作用所致。在类胡萝卜素区域观察到明显的寡聚依赖性差异，主要是由于在三聚体和低聚体光谱的509处出现了新的叶黄素吸收带。它被归因于一些叶黄素分子，与先前的实验观察一致。这些叶黄素分子的电光性质与LHCII中其他叶黄素分子的电光性质有很大的不同，它们在电子激发下偶极矩变化不大（| Δ μ→| =14.6±2.0 D/f）。当LHCII聚集时，一些额外的吸收出现在主Chl a qy吸收带的红色一侧。与先前的建议相反[J]。理论物理。化学。[A 103(1999) 2422]，没有发现相应波段的电荷转移特征。讨论了新黄质和叶黄素在LHCII中s2电子跃迁的归属以及Stark效应的可能起源。
The electric field-induced absorption changes (Stark effect) of light-harvesting complex II (LHCII) in different oligomerisation states—monomeric, trimeric and aggregated—have been probed at 77 K. All the chlorophyll (Chl) a molecules exhibit electro-optic properties in the Qyabsorption region characterized by a change in dipole moment | Δ μ → |=0.6±0.06 D/f and polarizability, Tr(Δα̃)∼55±5 Å3/f2upon electronic excitation, which are similar to those of unbound monomeric Chl a, indicating the absence of strong delocalization of the excitations which would be expected in the presence of strong excitonic interactions. The Stark effect in the Chl b absorption region is significantly bigger with | Δ μ → | values of the order of 2.0±0.2 D/f and it is attributed to strong interactions with neoxanthin molecules. Clear oligomerisation-dependent differences are observed in the carotenoid region, mainly due to the appearance of a new xanthophyll absorption band at 509 in the spectra of trimers and oligomers. It is ascribed to some lutein molecules, in agreement with previous experimental observations. The electro-optic properties of these lutein molecules are significantly different from those of the other xanthophylls in LHCII, which do not exhibit such a big change in dipole moment upon electronic excitation (| Δ μ → | =14.6±2.0 D/f). Upon aggregation of LHCII some extra absorption appears on the red side of the main Chl a Qyabsorption band. In contrast to an earlier suggestion [J. Phys. Chem., A 103 (1999) 2422], no indications are found for the charge-transfer character of the corresponding band. The assignments of the S2electronic transitions of neoxanthin and lutein in LHCII and possible origins of the Stark effect are discussed.