Chiou H C, Blankenship R E
Department of Chemistry and Biochemistry, Arizona State University, Tempe, USA.
Photochem Photobiol. 1996 Jul;64(1):32-7. doi: 10.1111/j.1751-1097.1996.tb02418.x.
Transient absorption difference spectroscopy was used to study the temperature dependence of the P798+ decay kinetics in heliobacteria. For membrane samples, two components were obtained from the fitting of kinetic traces in the temperature range of 4-29 degrees C. A 3-9 ms component representing the cytochrome (cyt) c oxidation has an activation energy of 33.0 +/- 2.8 kJ/mol. A 12-22 ms component representing either P798+FX- or P798+FA/B- recombination has an activation energy of 15.3 +/- 2.4 kJ/mol. In isolated reaction centers (RC), only one 14 ms component due to P798+FX- recombination was obtained in this temperature range. The Arrhenius plot shows that the recombination rate of this P798+FX- state is temperature independent in the near room temperature range. For RC in the temperature range of 60-298 K, a 12-15 ms decay was obtained at temperatures greater than 240 K. Biphasic decay traces (12-15 ms and 2-4 ms components) were obtained at temperatures between 170 K and 230 K. Only one 2-4 ms component was found at temperatures lower than 160 K. The gradual switchover from the 12-15 ms to the 2-4 ms component upon cooling may indicate the shift of the P798+FX- recombination state to a state that is prior to P798+FX-, although other interpretations can not be excluded. The absorption difference spectrum (delta A @ 160 K - delta A @ 240 K) in the blue region shows a positive amplitude below 405 nm and a negative amplitude above 405 nm implying that the 2-4 ms decay component may be due to the recombination of P798+A1-, where A1 is a quinone-type acceptor.
瞬态吸收差光谱法被用于研究嗜盐菌中P798⁺衰减动力学的温度依赖性。对于膜样品，在4至29摄氏度的温度范围内，通过对动力学曲线的拟合得到了两个成分。一个代表细胞色素（cyt）c氧化的3至9毫秒成分，其活化能为33.0±2.8千焦/摩尔。一个代表P798⁺FX⁻或P798⁺FA/B⁻重组的12至22毫秒成分，其活化能为15.3±2.4千焦/摩尔。在分离的反应中心（RC）中，在该温度范围内仅获得了一个由于P798⁺FX⁻重组产生的14毫秒成分。阿累尼乌斯图表明，在接近室温的范围内，该P798⁺FX⁻状态的重组速率与温度无关。对于温度在60至298K范围内的RC，在温度高于240K时获得了12至15毫秒的衰减。在170K至230K之间的温度下获得了双相衰减曲线（12至15毫秒和2至4毫秒成分）。在温度低于160K时仅发现了一个2至4毫秒成分。冷却时从12至15毫秒成分到2至4毫秒成分的逐渐转变可能表明P798⁺FX⁻重组状态转变为P798⁺FX⁻之前的状态，尽管不能排除其他解释。蓝色区域的吸收差光谱（δA @ 160K - δA @ 240K）在405nm以下显示正振幅，在405nm以上显示负振幅，这意味着2至4毫秒的衰减成分可能是由于P798⁺A1⁻的重组，其中A1是一种醌型受体。
