EVIDENCE THAT A DISTRIBUTION OF BACTERIAL REACTION CENTERS UNDERLIES THE TEMPERATURE AND DETECTION-WAVELENGTH DEPENDENCE OF THE RATES OF THE PRIMARY ELECTRON-TRANSFER REACTIONS
EVIDENCE THAT A DISTRIBUTION OF BACTERIAL REACTION CENTERS UNDERLIES THE TEMPERATURE AND DETECTION-WAVELENGTH DEPENDENCE OF THE RATES OF THE PRIMARY ELECTRON-TRANSFER REACTIONS
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DOI：
10.1073/pnas.87.9.3552
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发表时间：
1990-05-01
影响因子：
11.1
通讯作者：
HOLTEN, D
中科院分区：
文献类型：
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作者：
KIRMAIER, C;HOLTEN, D
利用870 nm的150 fs激发闪光，详细研究了类球红细菌反应中心的初级电子转移速率。在室温下，两个初始电荷分离的表观时间常数（P* →P+BPhL-）和随后的电子转移（P+BPhL-→P+QA-）被发现包含一个值范围（约1.3-4 ps和约分别为100-320 ps），这取决于遵循动力学的波长。我们认为这反映了反应中心（或一些构象异构体）的分布，具有不同的因素，如辅因子之间的距离或方向，氢键，或其他色素-蛋白质相互作用。我们还建议，在低温下观察到的时间常数（apprxeq. 1.3和. apprxeq. 100 ps，随检测波长的变化小得多或可忽略不计）并不反映速率随温度降低而实际增加，而是源自反应中心分布向其中电子转移固有地以更快速率发生的那些中心的偏移。
The rates of the primary electron-transfer processes in Rhodobacter sphaeroides reaction centers have been examined in detail by using 150-fs excitation flashes at 870 nm. At room temperature the apparent time constants for both initial charge separation (P* .fwdarw. P+BPhL-) and subsequent electron transfer (P+BPhL- .fwdarw. P+QA-) are found to encompass a range of values (.apprxeq. 1.3-4 ps and .apprxeq. 100-320 ps, respectively), depending on the wavelength at which the kinetics are followed. We suggest this reflects a distribution of reaction centers (or a few conformers), having differences in factors such as distances or orientations between the cofactors, hydrogen bonding, or other pigment-protein interactions. We also suggest that the time constants observed at cryogenic temperatures (.apprxeq. 1.3 and .apprxeq. 100 ps, respectively, with much smaller or negligible variation with detection wavelength) do not reflect an actual increase in the rates with decreasing temperature but rather derive from a shift in the distribution of reaction centers toward those in which electron transfer inherently occurs with the faster rates.