Mimuro M, Akimoto S, Yamazaki I, Miyashita H, Miyachi S
Department of Physics, Biology and Informatics, Faculty of Science, Yamaguchi University, Yoshida, Yamaguchi 753-8512, Japan.
Biochim Biophys Acta. 1999 May 26;1412(1):37-46. doi: 10.1016/s0005-2728(99)00048-1.
Antenna components and the primary electron donor of the photosystem (PS) II in the Chlorophyll (Chl) d-dominating prokaryote, Acaryochloris marina, were studied using time-resolved fluorescence spectroscopy in the ps time range. By selective excitation of Chl a or Chl d, differences in fluorescence properties were clearly resolved. At physiological temperature, energy transfer was confirmed by a red shift of emission maximum among PS II antenna components, and the equilibrium of energy distribution among Chl a and Chl d was established within 30 ps. A fluorescence component that can be assigned to delayed fluorescence (DF) was observed at 10 ns after the excitation; however, it was not necessarily resolved by the decay kinetics. At -196 degrees C, a red shift of emission maximum was reproduced but the equilibrium of energy distribution was not detected. DF was resolved in the wavelength region corresponding to Chl a by spectra and by decay kinetics. The lifetime of the DF was estimated to be approx. 15 ns, and the peaks were located at 681 and 695 nm, significantly shorter wavelengths than those of Chl d. These findings strongly suggest that an origin of DF is Chl a, and Chl a is most probably the primary electron donor in the PS II reaction center (RC). These results indicate that the constitution of PS II RC in this alga is essentially identical to that of other oxygenic photosynthetic organisms.
利用皮秒时间分辨荧光光谱技术，对叶绿素（Chl）d占主导的原核生物——滨海红藻中的天线组件和光系统（PS）II的初级电子供体进行了研究。通过选择性激发Chl a或Chl d，荧光特性的差异得以清晰分辨。在生理温度下，PS II天线组件发射最大值的红移证实了能量转移，并且Chl a和Chl d之间的能量分布平衡在30皮秒内得以建立。在激发后10纳秒观察到一个可归因于延迟荧光（DF）的荧光成分；然而，它不一定能通过衰减动力学分辨出来。在-196℃时，发射最大值的红移得以重现，但未检测到能量分布平衡。通过光谱和衰减动力学在对应于Chl a的波长区域分辨出了DF。DF的寿命估计约为15纳秒，其峰值位于681和695纳米处，波长明显短于Chl d。这些发现有力地表明DF的起源是Chl a，并且Chl a很可能是PS II反应中心（RC）的初级电子供体。这些结果表明，这种藻类中PS II RC的组成与其他产氧光合生物的基本相同。
