Schlodder Eberhard, Hussels Martin, Cetin Marianne, Karapetyan Navassard V, Brecht Marc
Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
Biochim Biophys Acta. 2011 Nov;1807(11):1423-31. doi: 10.1016/j.bbabio.2011.06.018. Epub 2011 Jul 13.
Photosystem I of cyanobacteria contains different spectral pools of chlorophylls called red or long-wavelength chlorophylls that absorb at longer wavelengths than the primary electron donor P700. We measured the fluorescence spectra at the ensemble and the single-molecule level at low temperatures in the presence of oxidized and reduced P700. In accordance with the literature, it was observed that the fluorescence is quenched by P700(+). However, the efficiency of the fluorescence quenching by oxidized P700(+) was found to be extremely different for the various red states in PS I from different cyanobacteria. The emission of the longest-wavelength absorbing antenna state in PS I trimers from Thermosynechococcus elongatus (absorption maximum at 5K: ≈ 719nm; emission maximum at 5K: ≈ 740nm) was found to be strongly quenched by P700(+) similar to the reddest state in PS I trimers from Arthrospira platensis emitting at 760nm at 5K. The fluorescence of these red states is diminished by more than a factor of 10 in the presence of oxidized P700. For the first time, the emission of the reddest states in A. platensis and T. elongatus has been monitored using single-molecule fluorescence techniques.
蓝细菌的光系统I含有不同光谱池的叶绿素，称为红色或长波长叶绿素，它们在比初级电子供体P700更长的波长处吸收。我们在氧化和还原的P700存在下，在低温下测量了整体和单分子水平的荧光光谱。与文献一致，观察到荧光被P700(+)猝灭。然而，发现氧化的P700(+)对来自不同蓝细菌的PS I中各种红色状态的荧光猝灭效率差异极大。发现来自嗜热栖热菌的PS I三聚体中吸收最长波长的天线状态（5K时吸收最大值：≈719nm；5K时发射最大值：≈740nm）的发射被P700(+)强烈猝灭，类似于来自钝顶节旋藻的PS I三聚体中在5K时发射波长为760nm的最红状态。在氧化的P700存在下，这些红色状态的荧光减弱超过10倍。首次使用单分子荧光技术监测了钝顶节旋藻和嗜热栖热菌中最红状态的发射。
