Department of Biophysics, Huygens Laboratory of the State University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands.
Photosynth Res. 1988 Feb;15(2):177-89. doi: 10.1007/BF00035261.
The transfer of excitation energy in intact cells of the thermophilic green photosynthetic bacterium Chloroflexus aurantiacus was studied both at low temperature and under more physiological conditions. Analysis of excitation spectra measured at 4K indicates that the minor fraction of bacteriochlorophyll a present in the chlorosome functions as an intermediate in energy transfer between the main light-harvesting pigment BChl c and the membrane-bound B808-866 antenna complex. This supports the hypothesis that BChl a is associated with the base plate which connects the chlorosome with the membrane. The overall efficiency for energy transfer from the chlorosome to the membrane is only 15% at 4K. High efficiencies of close to 100% are observed above 40°C near the temperature where the cultures are grown. Cooling to 20°C resulted in a sudden drop of the transfer efficiency which appeared to originate in the chlorosome. This decrease may be related to a lipid phase transition. Further cooling mainly affected the efficiency of transfer between the chlorosome and the membrane. This effect can only partially be explained by a decreased Förster overlap between the chlorosomal BChl a and BChl a 808 associated with the membrane-bound antenna system. The temperature dependence of the fluorescence yield of BChl a 866 also appeared to be affected by lipid phase transitions, suggesting that this fluorescence can be used as a native probe of the physical state of the membrane.
在低温和更接近生理条件下，研究了嗜热绿色光合细菌 Chloroflexus aurantiacus 完整细胞中激发能的转移。在 4K 下测量的激发光谱分析表明，在类囊体中存在的少量细菌叶绿素 a 作为主聚光色素 BChl c 和膜结合的 B808-866 天线复合物之间能量转移的中间物发挥作用。这支持了 BChl a 与连接类囊体与膜的基板有关的假设。在 4K 时，从类囊体到膜的能量转移的总效率仅为 15%。在接近培养物生长温度的 40°C 以上，观察到接近 100%的高效率。冷却到 20°C 导致转移效率突然下降，这种下降似乎起源于类囊体。这种下降可能与脂质相转变有关。进一步冷却主要影响类囊体和膜之间的转移效率。这种影响不能仅通过与膜结合的天线系统相关的类囊体 BChl a 和 BChl a 808 之间 Förster 重叠的减少来解释。BChl a 866 的荧光产率的温度依赖性似乎也受到脂质相转变的影响，表明这种荧光可以用作膜的物理状态的天然探针。
