Rathbone Harry W, Davis Jeffery A, Michie Katharine A, Goodchild Sophia C, Robertson Neil O, Curmi Paul M G
School of Physics, The University of New South Wales, Sydney, New South Wales, 2052, Australia.
Centre for Quantum and Optical Science, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, Victoria, 3122, Australia.
Biophys Rev. 2018 Oct;10(5):1443-1463. doi: 10.1007/s12551-018-0456-x. Epub 2018 Sep 22.
Considerable debate surrounds the question of whether or not quantum mechanics plays a significant, non-trivial role in photosynthetic light harvesting. Many have proposed that quantum superpositions and/or quantum transport phenomena may be responsible for the efficiency and robustness of energy transport present in biological systems. The critical experimental observations comprise the observation of coherent oscillations or "quantum beats" via femtosecond laser spectroscopy, which have been observed in many different light harvesting systems. Part Two of this review aims to provide an overview of experimental observations of energy transfer in the most studied light harvesting systems. Length scales, derived from crystallographic studies, are combined with energy and time scales of the beats observed via spectroscopy. A consensus is emerging that most long-lived (hundreds of femtoseconds) coherent phenomena are of vibrational or vibronic origin, where the latter may result in coherent excitation transport within a protein complex. In contrast, energy transport between proteins is likely to be incoherent in nature. The question of whether evolution has selected for these non-trivial quantum phenomena may be an unanswerable question, as dense packings of chromophores will lead to strong coupling and hence non-trivial quantum phenomena. As such, one cannot discern whether evolution has optimised light harvesting systems for high chromophore density or for the ensuing quantum effects as these are inextricably linked and cannot be switched off.
围绕量子力学在光合光捕获过程中是否发挥重要的、非平凡的作用这一问题，存在着相当多的争论。许多人提出，量子叠加和/或量子输运现象可能是生物系统中能量传输效率和稳健性的原因。关键的实验观测包括通过飞秒激光光谱法观测到的相干振荡或“量子拍”，这在许多不同的光捕获系统中都已被观测到。本综述的第二部分旨在概述在研究最多的光捕获系统中能量转移的实验观测情况。从晶体学研究中得出的长度尺度，与通过光谱法观测到的拍的能量和时间尺度相结合。一种共识正在形成，即大多数长寿命（数百飞秒）的相干现象起源于振动或振动电子，其中后者可能导致蛋白质复合物内的相干激发传输。相比之下，蛋白质之间的能量传输本质上可能是不相干的。进化是否选择了这些非平凡的量子现象这个问题可能是一个无法回答的问题，因为发色团的密集堆积会导致强耦合，从而产生非平凡的量子现象。因此，人们无法辨别进化是为了高发色团密度还是为了随之而来的量子效应而优化光捕获系统，因为这些是紧密相连且无法消除的。
