Excitation dynamics in the LHCII complex of higher plants:: Modeling based on the 2.72 Å crystal structure
Excitation dynamics in the LHCII complex of higher plants:: Modeling based on the 2.72 Å crystal structure
复制标题
DOI：
10.1021/jp044082f
复制
发表时间：
2005-05-26
影响因子：
3.3
通讯作者：
van Grondelle, R
中科院分区：
文献类型：
--
作者：
Novoderezhkin, VI;Palacios, MA;van Grondelle, R
我们使用新的结构数据模拟了外围植物光捕获复合体 LHCII 的稳态光谱和能量传递动力学（Liu, Z.；Yan, H.；Wang, K.；Kuang, T.；Zhang, J.；Gui, L.；An, X.；Chang, W. Nature. 2004, 428, 287）。叶绿素 (Chl) b -> Chl a 转移的动力学以及选择性激发“瓶颈”Chl a 和 b 态的衰变已通过飞秒泵浦探针光谱进行了研究。我们提出了 LHCII 三聚体（具有特定位点能量）的激子模型，该模型允许同时定量拟合不同波长激发时的吸收、线性二色性、稳态荧光光谱和瞬态吸收动力学。在建模中，我们使用实验激子声子谱密度和修正的雷德菲尔德理论。我们发现快速 b -> a 转移是由 Chls b 与强耦合 Chl a 簇（即 a610-a61-a612 三聚体以及 a602-a603 和 a613-a614 二聚体）的良好连接决定的。能量传递动力学的长寿命成分是由红移 Chl b605 和蓝移 Chl a604 的快速群体决定的，随后是非常慢的 b605 Q ps 和 a604 12 ps）从这些单体瓶颈位点到 Chl a 簇的能量流。叶绿素 a 区域内的动力学由 a610-a61-a612 三聚体内的快速（时间常数低至低于 100 fs）激子弛豫、a602-a603 和 a613-a614 二聚体内较慢的 200-300 fs 弛豫、这些团簇之间甚至更慢的 300-800 fs 迁移以及从 a604 到准分子团的非常缓慢的转移决定。 - 平衡了一个站点。最终平衡的特征是 a610-a611-a612 簇的主要种群（主要是 a610 位点）。该簇位于 LHCII 三聚体外侧，可能提供了与 PSII 其他亚基的良好连接。
We have modeled steady-state spectra and energy-transfer dynamics in the peripheral plant light-harvesting complex LHCII using new structural data (Liu, Z.; Yan, H.; Wang, K.; Kuang, T.; Zhang, J.; Gui, L.; An, X.; Chang, W. Nature. 2004, 428, 287). The dynamics of the chlorophyll (Chl) b -> Chl a transfer and decay of selectively excited "bottleneck" Chl a and b states have been studied by femtosecond pump-probe spectroscopy. We propose an exciton model of the LHCII trimer (with specific site energies) which allows a simultaneous quantitative fit of the absorption, linear-dichroism, steady-state fluorescence spectra, and transient absorption kinetics upon excitation at different wavelengths. In the modeling we use the experimental exciton phonon spectral density and modified Redfield theory. We have found that fast b -> a transfer is determined by a good connection of the Chls b to strongly coupled Chl a clusters, i.e., a610-a61-a612 trimer and a602-a603 and a613-a614 dimers. Long-lived components of the energy-transfer kinetics are determined by a quick population of red-shifted Chl b605 and blue-shifted Chl a604 followed by a very slow Q ps for b605 and 12 ps for a604) flow of energy from these monomeric bottleneck sites to the Chl a clusters. The dynamics within the Chl a region is determined by fast (with time constants down to sub-100 fis) exciton relaxation within the a610-a61-a612 trimer, slower 200-300 fs relaxation within the a602-a603 and a613-a614 dimers, even slower 300-800 fs migration between these clusters, and very slow transfer from a604 to the quasi -equilibrated a sites. The final equilibrium is characterized by predominant population of the a610-a611-a612 cluster (mostly the a610 site). The location of this cluster on the outer side of the LHCII trimer probably provides a good connection with the other subunits of PSII.