Picosecond infrared studies of the dynamics of the photosynthetic reaction center.
Picosecond infrared studies of the dynamics of the photosynthetic reaction center.
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光合反应中心动力学的皮秒红外研究。
DOI：
10.1073/pnas.90.11.5247
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发表时间：
1993
影响因子：
11.1
通讯作者：
Hochstrasser,RM
中科院分区：
文献类型：
--
作者：
Maiti,S;Cowen,BR;Diller,R;Iannone,M;Moser,CC;Dutton,PL;Hochstrasser,RM
通过皮秒红外光谱检测光合反应中心蛋白质和氧化还原辅助因子振动跃迁的变化。研究了电子转移光引发后 50 ps 至 4 ns 的水合和部分脱水反应中心的振动中红外区域 (1800-1550 cm-1) 的光谱。红外差异光谱的特征通过蛋白质和氧化还原辅因子振动模式来识别，并与在红外和可见光区域测量动力学的电子转移事件相关。观察到的蛋白质反应仅限于少数酰胺 I 转变（1644 cm-1、1661 cm-1、1665 cm-1）和羧基残基（1727 cm-1）。大约 85% 的观察到的信号对应于辅因子相关酯和酮羰基的变化。酰胺 I 和羧基转变出现在 50 ps 之前，表明初级电子转移事件与蛋白质骨架的特定片段以及特殊对附近的谷氨酸或天冬氨酸残基偶联。在所有研究时间中，伴随细菌叶绿素二聚体阳离子形成的红外吸收变化主导了信号。在水合反应中心和部分脱水反应中心观察到的红外光谱变化明显不同；水合蛋白质中 1665 cm-1 处光谱宽度为 6 cm-1 的谱带（对应于蛋白质酰胺 I 漂白剂）在脱水膜中不存在。这些差异是根据在水存在下观察到的明显不同的电子转移动力学来讨论的。
The changes in the vibrational transitions of the protein and redox cofactors of the photosynthetic reaction center were examined by picosecond infrared spectroscopy. The spectra in the vibrational mid-infrared region (1800-1550 cm-1) of hydrated and partially dehydrated reaction centers were investigated from 50 ps to 4 ns after photoinitiation of the electron transfer. Features in the infrared difference spectra were identified with both protein and redox cofactor vibrational modes and correlated with electron transfer events whose kinetics were measured in the infrared and visible regions. The observed protein response is confined to a few amide I transitions (1644 cm-1, 1661 cm-1, 1665 cm-1) and carboxylic residues (1727 cm-1). About 85% of the observed signal corresponded to alterations in the cofactor-associated ester and keto carbonyls. The amide I and carboxylic transitions appeared prior to 50 ps, suggesting that the primary electron transfer event is coupled with a specific piece of the protein backbone and to glutamic or aspartic residues nearby the special pair. Infrared absorption changes accompanying bacteriochlorophyll-dimer cation formation dominated the signal at all times investigated. Infrared spectral changes observed in hydrated and partially dehydrated reaction centers were distinctly different; a band at 1665 cm-1 with a spectral width of 6 cm-1 in the hydrated protein, corresponding to a protein amide I bleach, was not present in the dehydrated film. These differences are discussed in terms of the markedly different electron transfer kinetics observed in the presence of water.