Department of Biophysics, Huygens Laboratory of the State University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
Proc Natl Acad Sci U S A. 1980 Oct;77(10):5889-93. doi: 10.1073/pnas.77.10.5889.
At room temperature the delayed fluorescence (luminescence) of spinach chloroplasts, in which the acceptor Q is prereduced, consists of a component with a lifetime of 0.7 mus and a more rapid component, presumably with a lifetime of 100-200 ns and about the same integrated intensity as the 0.7- mus component. Between 4.2 and 200 K only a 100- to 200-ns luminescence component was found, with an integrated intensity appreciably larger than that at room temperature. At 77 K the 150-ns component approached 63% of saturation at roughly the same energy as the variable fluorescence of photosystem II at room temperature. At 77 K the emission spectra of prompt fluorescence but not that of the 150-ns luminescence had a preponderant additional band at about 735 nm. The 150-ns emission also occurred in the photosystem I-lacking mutant FL5 of Chlamydomonas. These experiments indicate that the 150-ns component originates from photosystem II. At room temperature a magnetic field of 0.22 T stimulated the 0.7-mus delayed fluorescence by about 10%. At 77 K the field-induced increase of the 150-ns component amounted to 40-50%, being responsible for the observed approximately 2% increase of the total emission; the magnetic field increased the lifetime about 20%. In order to explain these phenomena a scheme for photosystem II is presented with an intermediary acceptor W between Q and the primary donor chlorophyll P-680; recombination of P-680(+) and W(-) causes the fast luminescence. The magnetic field effect on this emission is discussed in terms of the radical pair mechanism.
在室温下，接受体 Q 预先还原的菠菜叶绿体的延迟荧光（发光）由一个寿命为 0.7 微秒的组分和一个更快的组分组成，其寿命可能为 100-200 纳秒，并且与 0.7-微秒组分的积分强度相同。在 4.2 至 200 K 之间，仅发现了 100-200 纳秒的发光组分，其积分强度明显大于室温下的积分强度。在 77 K 时，150 纳秒的组分在与室温下的光系统 II 可变荧光大致相同的能量下接近 63%的饱和。在 77 K 时，瞬时光荧光的发射光谱但不是 150 纳秒发光的发射光谱在约 735nm 处具有占主导地位的附加带。150 纳秒的发射也发生在 Chlamydomonas 的缺乏光系统 I 的突变体 FL5 中。这些实验表明，150 纳秒的组分源自光系统 II。在室温下，0.22 T 的磁场将 0.7 微秒的延迟荧光刺激增加了约 10%。在 77 K 时，磁场诱导的 150 纳秒组分的增加量达到 40-50%，这导致了观察到的总发射增加约 2%；磁场将寿命延长了约 20%。为了解释这些现象，提出了一种光系统 II 的方案，其中 Q 和初级供体叶绿素 P-680 之间存在中介接受体 W；P-680(+)和 W(-)的复合导致快速发光。磁场对这种发射的影响根据自由基对机制进行了讨论。
