First-Principles Models for Biological Light-Harvesting: Phycobiliprotein Complexes from Cryptophyte Algae
First-Principles Models for Biological Light-Harvesting: Phycobiliprotein Complexes from Cryptophyte Algae
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DOI：
10.1021/jacs.7b01780
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发表时间：
2017-06-14
影响因子：
15
通讯作者：
Coker, David F.
中科院分区：
文献类型：
--
作者：
Lee, Mi Kyung;Bravaya, Ksenia B.;Coker, David F.
已经有许多实验和理论方面的努力，试图将模型哈密顿量参数化，以描述光合作用光收集系统中的激发态能量转移。Frenkel激子模型，其一组电子耦合的两能级发色团，每个发色团都线性耦合到谐振子的耗散槽，已经成为该领域的主力。对这类哈密顿量进行参数化的挑战在于它们的独特性和物理解释。在这里，我们提出了一种计算方法，该方法使用精确的第一性原理电子结构方法来计算局部极小值集合的独特模型参数，这些极小值通过分子动力学和QM几何优化进行采样，从而构建局部模型集合，捕获这些系统在固有结构的局部盆地之间移动时的波动。该方法的准确性、鲁棒性和可靠性在隐藻藻胆蛋白光收集复合体的应用中得到了验证。我们计算的哈密顿系综提供了非均匀展宽过程的第一性原理描述，并使用标准近似的非马尔可夫简化密度矩阵动力学描述来估计由电子振动耦合引起的谱线形状的寿命展宽贡献。尽管这种近似线形理论引起了过宽，但我们证明了我们的模型哈密顿系综方法能够为计算光谱提供可靠的完全第一性原理方法，并且可以在实验结果中区分不同发色团质子化状态的影响。这些系统动力学的一个关键特征是在电子激发和能量转移的基础上激发色团内部振动。我们证明，哈密顿系综方法为这些贡献提供了可靠的第一性原理描述，这些贡献在最近的宽带泵浦探针和二维电子光谱实验中得到了详细说明。
There have been numerous efforts, both experimental and theoretical, that have attempted to parametrize model Hamiltonians to describe excited state energy transfer in photosynthetic light harvesting systems. The Frenkel exciton model, with its set of electronically coupled two level chromophores that are each linearly coupled to dissipative baths of harmonic oscillators, has become the workhorse of this field. The challenges to parametrizing such Hamiltonians have been their uniqueness, and physical interpretation. Here we present a computational approach that uses accurate first-principles electronic structure methods to compute unique model parameters for a collection of local minima that are sampled with molecular dynamics and QM geometry optimization enabling the construction of an ensemble of local models that captures fluctuations as these systems move between local basins of inherent structure. The accuracy, robustness, and reliability of the approach is demonstrated in an application to the phycobiliprotein light harvesting compleies from cryptophyte algae. Our computed Hamiltonian ensemble provides a first-principles description of inhomogeneous broadening processes, and a standard approximate non-Markovian reduced density matrix dynamics description is used to estimate lifetime broadening contributions to the spectral line shape arising from electronic vibrational coupling. Despite the overbroadening arising from this approximate line shape theory, we demonstrate that our model Hamiltonian ensemble approach is able to provide a reliable fully first-principles method for computation of spectra and can distinguish the influence of different chromophore protonation states in experimental results. A key feature in the dynamics of these systems is the excitation of intrachromophore vibrations upon electronic excitation and energy transfer. We demonstrate that the Hamiltonian ensemble approach provides a reliable first-principles description of these contributions that have been :detailed in recent broad-band pump probe and two-dimensional electronic spectroscopy experiments.