Structure-Based Calculations of Optical Spectra of Photosystem I Suggest an Asymmetric Light-Harvesting Process
Structure-Based Calculations of Optical Spectra of Photosystem I Suggest an Asymmetric Light-Harvesting Process
复制标题
DOI：
10.1021/ja9072222
复制
发表时间：
2010-03-17
影响因子：
15
通讯作者：
Renger, Thomas
中科院分区：
文献类型：
--
作者：
Adolphs, Julian;Mueh, Frank;Renger, Thomas
光学线形理论结合量子化学/静电计算96种叶绿素a色素及其激子耦合的位能，模拟了长热共生球菌光系统I核心配合物的光谱。基于2.5埃晶体结构计算的吸光度、线性二色性和圆二色性光谱与实验数据半定量匹配，从而可以对色素蛋白相互作用进行详细分析。大多数位能是由与大量氨基酸残基的多重相互作用决定的，这一结果表明了远程静电相互作用的重要性。发现天线的低能激子态位于离反应中心特殊对最近的约25 a处。中间色素形成了一个高能量的桥梁，其位能被特别多的氨基酸残基（bbb100）所稳定。低能激子态在反应中心a支侧的天线集中较大，这意味着激发能不对称地传递给后者。光收集中的这种不对称可能为理解两个分支在初级电子转移反应中的不对称使用提供了关键。建议通过实验来验证这种可能性。
Optical line shape theory is combined with a quantum-chemical/electrostatic calculation of the site energies of the 96 chlorophyll a pigments and their excitonic couplings to simulate optical spectra of photosystem I core complexes from Thermosynechococcus elongatus. The absorbance, linear dichroism and circular dichroism spectra, calculated on the basis of the 2.5 angstrom crystal structure, match the experimental data semiquantitatively allowing for a detailed analysis of the pigment protein interaction. The majority of site energies are determined by multiple interactions with a large number (>20) of amino acid residues, a result which demonstrates the importance of long-range electrostatic interactions. The low-energy exciton states of the antenna are found to be located at a nearest distance of about 25 A from the special pair of the reaction center. The intermediate pigments form a high-energy bridge, the site energies of which are stabilized by a particularly large number (>100) of amino acid residues. The concentration of low energy exciton states in the antenna is larger on the side of the A-branch of the reaction center, implying an asymmetric delivery of excitation energy to the latter. This asymmetry in light-harvesting may provide the key for understanding the asymmetric use of the two branches in primary electron transfer reactions. Experiments are suggested to check for this possibility.