Bijvoet Centre for Biomolecular Research, University of Utrecht, Heidelberglaan 8, 3584 CS Utrecht, The Netherlands.
Institute of Theoretical Physics, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria.
J Phys Chem Lett. 2020 Dec 17;11(24):10306-10314. doi: 10.1021/acs.jpclett.0c03123. Epub 2020 Nov 23.
Inhomogeneous broadening of optical lines of the Fenna-Matthews-Olson (FMO) light-harvesting protein is investigated by combining a Monte Carlo sampling of low-energy conformational substates of the protein with a quantum chemical/electrostatic calculation of local transition energies (site energies) of the pigments. The good agreement between the optical spectra calculated for the inhomogeneous ensemble and the experimental data demonstrates that electrostatics is the dominant contributor to static disorder in site energies. Rotamers of polar amino acid side chains are found to cause bimodal distribution functions of site energy shifts, which can be probed by hole burning and single-molecule spectroscopy. When summing over the large number of contributions, the resulting distribution functions of the site energies become Gaussians, and the correlations in site energy fluctuations at different sites practically average to zero. These results demonstrate that static disorder in the FMO protein is in the realm of the central limit theorem of statistics.
采用蒙特卡罗方法对 Fenna-Matthews-Olson（FMO）光捕获蛋白的低能构象亚稳态进行抽样，并结合量子化学/静电计算色素的局部跃迁能（局域能），研究了光吸收线的非均匀展宽。对非均匀系综计算的光学光谱与实验数据之间的良好吻合表明，静电作用是局域能静态无序的主要贡献者。发现极性氨基酸侧链的旋转异构体导致局域能位移的双峰分布函数，可以通过孔烧蚀和单分子光谱来探测。当对大量贡献进行求和时，局域能的分布函数成为高斯分布，不同局域的局域能波动之间的相关性实际上平均为零。这些结果表明，FMO 蛋白中的静态无序处于统计中心极限定理的范畴。
