Nagarajan V, Parson W W
Department of Biochemistry, University of Washington, Seattle 98195, USA.
Biochemistry. 1997 Feb 25;36(8):2300-6. doi: 10.1021/bi962534b.
Energy transfer between the B850 (LH2) and B875 (LH1) antenna complexes of a mutant strain of Rhodobacter sphaeroides lacking reaction centers is investigated by femtosecond pump-probe spectroscopy at room temperature. Measurements are made at wavelengths between 810 and 910 nm at times extending to 200 ps after selective excitation of either B850 or B875. Assignments of the spectroscopic signals to the two types of antenna complex are made on the basis of measurements in strains that lack either LH1 or LH2 in addition to reaction centers. Energy transfer from excited B850 to B875 proceeds with two time constants, 4.6 +/- 0.3 and 26.3 +/- 1.0 ps, but a significant fraction of the excitations remain in B850 for considerably longer times. The fast step is interpreted as hopping of energy to LH1 from an associated LH2 complex; the slower steps are interpreted as migration of excitations in the LH2 pool preceding transfer to LH1. Transfer of excitations from B875 to B850 could not be detected, possibly suggesting that the average number of LH2 complexes in contact with each LH1 is small.
利用飞秒泵浦-探测光谱技术在室温下研究了缺乏反应中心的球形红细菌突变株的B850（LH2）和B875（LH1）天线复合物之间的能量转移。在选择性激发B850或B875后，在810至910nm波长下进行测量，时间延长至200ps。除了反应中心外，根据在缺乏LH1或LH2的菌株中的测量结果，将光谱信号分配给两种类型的天线复合物。从激发态的B850到B875的能量转移有两个时间常数，分别为4.6±0.3和26.3±1.0ps，但相当一部分激发态在B850中保留的时间长得多。快速步骤被解释为能量从相关的LH2复合物跳跃到LH1；较慢的步骤被解释为激发态在转移到LH1之前在LH2库中的迁移。未检测到从B875到B850的激发态转移，这可能表明与每个LH1接触的LH2复合物的平均数量很少。
