Protein Arrangement Effects on the Exciton Dynamics in the PE555 Complex.
Protein Arrangement Effects on the Exciton Dynamics in the PE555 Complex.
复制标题
DOI：
10.1021/acs.jpcb.6b05803
复制
发表时间：
2017-04
期刊：
影响因子：
--
通讯作者：
Suryanarayanan Chandrasekaran;K. Pothula;U. Kleinekathöfer
中科院分区：
文献类型：
--
作者：
Suryanarayanan Chandrasekaran;K. Pothula;U. Kleinekathöfer
详细研究了藻胆蛋白天线复合物PE 555的环境耦合及其激子能量传递机制。通过分子动力学模拟，计算了分子沿经典基态轨道沿着的垂直跃迁能。为此，发现PE 555复合物的能级分布与PE 545复合物的能级分布相似，尽管各自的蛋白质结构存在明显差异。在PE 555复合物中，与PE 545结构相比，两个αβ单体旋转约73°，导致充满水的通道。此外，在这些聚集体中充当色素的胆色素与蛋白质之间的连接在两种结构中显示出明显的差异。然而，分析单个发色团与蛋白质环境的耦合，在两种蛋白质复合物中产生了相似的光谱密度。此外，已确定的部分过渡电荷的参与胆色素，以计算电子耦合使用过渡电荷从静电势（TrEsp）的方法。为了比较的目的，耦合已经提取使用点偶极子近似以及。平均而言，偶极近似预测的耦合值略大于那些从TrEsp方法导致增强人口衰减率测试在整体平均波包动力学。此外，在PE555结构中的激子动力学是显着慢于在PE545复合物由于较小的耦合值诱导的单体的不同的安排。
The environmental coupling of the phycobiliprotein antenna complex PE555 and its excitonic energy transfer mechanisms are studied in detail. Molecular dynamics simulations were performed followed by calculations of the vertical transition energies along the classical ground-state trajectory. To this end, the distributions of energy levels for the PE555 complex were found to be similar to those of the PE545 complex despite the clear differences in the respective protein structures. In the PE555 complex the two αβ monomers are rotated by ∼73° compared to the PE545 structure leading to a water filled channel. Moreover, the connections between the bilins, which act as pigments in these aggregates, and the protein show clear differences in the two structures. Analyzing the coupling of the individual chromophores to the protein environment, however, yielded similar spectral densities in the two protein complexes. In addition, the partial transition charges of the involved bilins have been determined in order to calculate the electronic couplings using the transition charges from electrostatic potentials (TrEsp) method. For comparison purposes, the couplings have been extracted using the point-dipole approximation as well. On average the coupling values predicted by the dipole approximation are slightly larger than those from the TrEsp method leading to enhanced population decay rates as tested in ensemble-averaged wave packet dynamics. Moreover, the exciton dynamics in the PE555 structure is significantly slower than in the PE545 complex due to the smaller coupling values induced by the dissimilar arrangements of the monomers.