光合作用多色素捕光模型中光激发对能量传输的影响

Influence of the light excitation on energy transfer in a multipigments light-harvesting model of photosynthesis

光合作用激发能传输过程中量子效应的研究大都基于单激发初态假设,该假设能较好地描述人们所关心的部分光合作用系统的初态.但对于不满足上述假设条件的自然及人工光合作用系统,激发过程对系统动力学有不可忽略的影响.本文基于由高斯脉冲激发的多色素分子模型,主要研究了激发脉冲宽度和激发间隔对系统动力学和激发能传输效率的影响.首先,推导了理论上可包含任意数量的色素分子构成的供体系统和受体系统整体演化所满足的动力学方程.之后通过数值模拟展示了激发能传输效率随系统各相关参数变化的关系及相应参数的最优范围.研究发现,在单个脉冲激发供体色素分子的条件下,存在最优脉冲宽度,且脉冲宽度对色素分子数目、耦合强度及退相位速率的最优范围都有调制作用,并分析了该调制作用的产生机制.在两个高斯脉冲依次激发供体色素分子的条件下,存在最优脉冲宽度及脉冲间隔的组合.本文得到的动力学方程可推广到其他形式的激发脉冲,得到的数值结果及优化设计原则对工作在不同光照条件下的人工光合作用系统的优化设计具有参考意义.

Most studies on quantum effects in the process of excitation energy transfer in photosynthesis system are based on the single-excitation initial state hypothesis,which can well describe the initial state of some photosynthesis systems that people are concerned about.But for natural and artificial photosynthesis systems that do not meet the above hypothesis,the excitation process has a non-negligible impact on the system dynamics.Based on a multi-pigments model excited by Gaussian pulse,the effects of the excitation pulse width and the excitation interval on system dynamics and excitation energy transfer efficiency are studied.First,the kinetic equations for the overall evolution of the donor system and the acceptor system that can theoretically contain any number of pigments are derived.Afterwards,the relationship between the excitation energy transfer efficiency and the related parameters of the system,as well as the optimal range of the corresponding parameters are demonstrated by numerical simulation.It is found that under the condition of donor pigments being excited by a single Gaussian pulse,there exists optimal pulse width,and the optimal range of the pigment molecule numbers,the coupling strength as well as the dephasing rate can be modulated by the pulse width.The mechanism of the above modulation is also analyzed and presented.Under the condition of donor pigments being excited by two Gaussian pulses sequentially,there exists an optimal combination of pulse width and pulse interval.The kinetic equations obtained in this paper can be extended to other forms of excitation pulses.The numerical results and the related optimal design principles obtained have reference significance for the optimal design of artificial photosynthesis systems under different light conditions.