Different Types of Vibrations Interacting with Electronic Excitations in Phycoerythrin 545 and Fenna-Matthews-Olson Antenna Systems
Different Types of Vibrations Interacting with Electronic Excitations in Phycoerythrin 545 and Fenna-Matthews-Olson Antenna Systems
复制标题
DOI：
10.1021/jz501351p
复制
发表时间：
2014-09-18
影响因子：
5.7
通讯作者：
Kleinekathoefer, Ulrich
中科院分区：
文献类型：
--
作者：
Aghtar, Mortaza;Struempfer, Johan;Kleinekathoefer, Ulrich
海藻的藻红蛋白545（PE 545）光合天线系统和绿色硫细菌的Fenna-Matthews-Olson（FMO）复合物的长寿命量子相干现象被报道以来，人们对这些复合物的兴趣急剧增加。对于PE 54.5复合物，这种现象即使在环境温度下也清晰可见，而对于FMO系统，这种现象在较低温度下更突出。阐明环境在这些长寿命量子效应中的作用的关键是光谱密度。在这里，我们采用分子动力学模拟与量子化学计算相结合，研究生物环境和PE 545中胆色素分子的垂直激发能之间的耦合，并将其与FMO复合物的先前计算进行比较。结果发现，所得到的谱密度的PE 545系统的整体强度是类似的实验为基础的同行，但也在FMO复杂的。然而，分子分析表明，在低频范围内的光谱密度的起源，这是最重要的激子跃迁，是完全不同的。在FMO的情况下，光谱密度的这一部分是由于环境波动，而在PE 545的情况下，它基本上只是由于胆色素分子的内部模式。这一发现为长寿命量子相干性的可能解释提供了新的线索，并且在不同的系统中，原因可能实际上是不同的。
The interest in the phycoerythrin 545 (PE545) photosynthetic antenna system of marine algae and the Fenna-Matthews-Olson (FMO) complex of green sulfur bacteria has drastically increased since long-lived quantum coherences were reported for these complexes. For the PE54.5 complex, this phenomenon is clearly visible even at ambient temperatures, while for the FMO system it is more prominent at lower temperatures. The key to elucidate the role of the environment in these long-lived quantum effects is the spectral density. Here, we employ molecular dynamics simulations combined with quantum chemistry calculations to study the coupling between the biological environment and the vertical excitation energies of the bilin pigment molecules in PE545 and compare them to prior calculations on the FMO complex. It is found that the overall strength of the resulting spectral densities for the PE545 system is similar to the experiment-based counterpart but also to those in the FMO complex. Molecular analysis, however, reveals that the origin for the spectral densities in the low frequency range, which is most important for excitonic transitions, is entirely different. In the case of FMO, this part of the spectral density is due to environmental fluctuations, while, in case of PE545, it is essentially only due to internal modes of the bilin molecules. This finding sheds new light on possible explanations of the long-lived quantum coherences and that the reasons might actually be different in dissimilar systems.