Department of Physics, Concordia University, Montreal, Quebec, Canada.
J Phys Chem B. 2011 Mar 31;115(12):2737-47. doi: 10.1021/jp108775y. Epub 2011 Mar 10.
The parameters of barrier distributions on the protein energy landscape in the excited electronic state of the pigment/protein system have been determined by means of spectral hole burning for the lowest-energy pigments of CP43 core antenna complex and CP29 minor antenna complex of spinach Photosystem II (PS II) as well as of trimeric and monomeric LHCII complexes transiently associated with the pea Photosystem I (PS I) pool. All of these complexes exhibit sixty to several hundred times lower spectral hole burning yields as compared with molecular glassy solids previously probed by means of the hole growth kinetics measurements. Therefore, the entities (groups of atoms), which participate in conformational changes in protein, appear to be significantly larger and heavier than those in molecular glasses. No evidence of a small (∼1 cm(-1)) spectral shift tier of the spectral diffusion dynamics has been observed. Therefore, our data most likely reflect the true barrier distributions of the intact protein and not those related to the interface or surrounding host. Possible applications of the barrier distributions as well as the assignments of low-energy states of CP29 and LHCII are discussed in light of the above results.
通过光谱烧孔法，确定了色素/蛋白质体系激发电子态下蛋白质能量景观上势垒分布的参数。研究对象为菠菜 PS II 中 CP43 核心天线复合物和 CP29 次要天线复合物的最低能量色素，以及与豌豆 PS I 池暂时相关的三聚体和单体 LHCII 复合物。与之前通过孔生长动力学测量研究的分子玻璃固体相比，所有这些复合物的光谱烧孔产率都低 60 到几百倍。因此，参与蛋白质构象变化的实体（原子群）似乎比分子玻璃中的实体大且重得多。没有观察到光谱扩散动力学的小（约 1 cm^-1）光谱移动层的证据。因此，我们的数据很可能反映了完整蛋白质的真实势垒分布，而不是与界面或周围宿主相关的势垒分布。根据上述结果，讨论了势垒分布的可能应用以及 CP29 和 LHCII 低能态的分配。
