Section of Plant Biology, Cornell University, 14853-5908, Ithaca, NY, USA.
Photosynth Res. 1990 Jun;24(3):201-8. doi: 10.1007/BF00032307.
Thermal emission and photochemical energy storage were examined in photosystem I reaction center/core antenna complexes (about 40 Chl a/P700) using photoacoustic spectroscopy. Satisfactory signals could only be obtained from samples bound to hydroxyapatite and all samples had a low signal-to-noise ratio compared to either PS I or PS II in thylakoid membranes. The energy storage signal was saturated at low intensity (half saturation at 1.5 W m(-2)) and predicted a photochemical quantum yield of >90%. Exogenous donors and acceptors had no effect on the signal amplitudes indicating that energy storage is the result of charge separation between endogenous components. Fe(CN)6 (-3) oxidation of P700 and dithionite-induced reduction of acceptors FA-FB inhibited energy storage. These data are compatible with the hypothesis that energy storage in PS I arises from charge separation between P700 and Fe-S centers FA-FB that is stable on the time scale of the photoacoustic modulation. High intensity background light (160 W m(-2)) caused an irreversible loss of energy storage and correlated with a decrease in oxidizable P700; both are probably the result of high light-induced photoinhibition. By analogy to the low fluorescence yield of PS I, the low signal-to-noise ratio in these preparations is attributed to the short lifetime of Chl singlet excited states in PS I-40 and its indirect effect on the yield of thermal emission.
用光声光谱法研究了光合作用系统 I 反应中心/核心天线复合物（约 40 个 Chl a/P700）中的热发射和光化学能量存储。只有与羟基磷灰石结合的样品才能获得令人满意的信号，与类囊体膜中的 PS I 或 PS II 相比，所有样品的信号噪声比都较低。能量存储信号在低强度下饱和（半饱和强度为 1.5 W m(-2))，预测光化学量子产率>90%。外源性供体和受体对信号幅度没有影响，表明能量存储是内源性组件之间电荷分离的结果。P700 的 Fe(CN)6 (-3)氧化和受体 FA-FB 的连二亚硫酸钠诱导还原抑制了能量存储。这些数据与以下假设一致，即在 PS I 中的能量存储源自 P700 和 FA-FB 之间的电荷分离，这种分离在光声调制的时间尺度上是稳定的。高强度背景光（160 W m(-2))会导致能量存储不可逆损失，并与可氧化 P700 的减少相关；这两者可能都是高光诱导光抑制的结果。与 PS I 低荧光产率类似，这些制剂中的低信号噪声比归因于 PS I-40 中 Chl 单重激发态的短寿命及其对热发射产率的间接影响。
