Department of Chemistry, P.O. Box 35, University of Jyväskylä , FIN-40014, Finland.
J Phys Chem B. 2013 Sep 26;117(38):11144-61. doi: 10.1021/jp4011394. Epub 2013 Aug 1.
A description of intra-chlorosome and from chlorosome to baseplate excitation energy transfer in green sulfur bacteria and in filamentous anoxygenic phototrophs is presented. Various shapes and sizes, single and multiwalled tubes, cylindrical spirals and lamellae of the antenna elements mimicking pigment organization in chlorosomes were generated by using molecular mechanics calculations, and the absorption, LD, and CD spectra of these were predicted by using exciton theory. Calculated absorption and LD spectra were similar for all modeled antenna structures; on the contrary, CD spectra turned out to be sensitive to the size and pigment orientations in the antenna. It was observed that, bringing two tubular antennae at close enough interaction distance, the exciton density of the lowest energy state became localized on pigments facing each other in the antenna dimer. Calculations predicted for stacked tubular antenna elements extremely fast, faster than 500 fs, intra-chlorosome energy transfer toward the baseplates in the direction perpendicular to the chlorosome long axis. Downhill excitation energy transfer according to our model is driven by interactions of the antennae with their immediate surroundings. Energy transfer from the chlorosome to the baseplate, consisting of 2D lattices of monomeric and dimeric bacteriochlorophyll a molecules, was predicted to occur in 5-15 ps, in agreement with experimental findings. Advancement of excitation through a double tube antenna stack, a model for antenna element organization in chlorosomes of green sulfur bacteria, to a monomeric baseplate was visualized in space and in time.
介绍了绿硫细菌和丝状无放氧光合作用菌中类囊体内和类囊体到基片的激发能量转移的描述。使用分子力学计算生成了天线元件的各种形状和大小，包括单壁和多壁管、圆柱形螺旋和类囊体天线的薄片，模拟了类囊体中的色素组织，并用激子理论预测了这些天线的吸收、LD 和 CD 光谱。所有模拟的天线结构的计算吸收和 LD 光谱都相似；相反，CD 光谱对天线中尺寸和色素取向敏感。观察到，当两个管状天线相互接近到足够的相互作用距离时，最低能量状态的激子密度在天线二聚体中彼此相对的色素上局部化。计算预测堆叠管状天线元件之间的类囊体内部能量转移在垂直于类囊体长轴的方向上非常快，快于 500 fs。根据我们的模型，下坡激发能量转移是由天线与其周围环境的相互作用驱动的。从类囊体到由单体和二聚体细菌叶绿素 a 分子组成的二维晶格的基片的能量转移预计在 5-15 ps 内发生，与实验结果一致。通过双管天线堆叠（绿硫细菌类囊体中天线元件组织的模型）将激发推进到单体基片，在空间和时间上进行了可视化。
