Searle G F, Tredwell C J, Barber J, Porter G
Biochim Biophys Acta. 1979 Mar 15;545(3):496-507. doi: 10.1016/0005-2728(79)90158-0.
Picosecond time-resolved fluorescence spectroscopy has been used to investigate the fluorescence emission from wild-type barley chloroplasts and from chloroplasts of the barley mutant, chlorina f-2, which lacks the light-harvesting chlorophyll a/b-protein complex. Cation-controlled regulation of the distribution of excitation energy was studied in isolated chloroplasts at the Fo and Fm levels. It was found that: (a) The fluorescence decay curves were distinctly non-exponential, even at low excitation intensities (less than 2 x 10(14) photons . cm(-2). (b) The fluorescence decay curves could, however, be described by a dual exponential decay law. The wild-type barley chloroplasts gave a short-lived fluorescence component of approximately 140 ps and a long-lived component of 600 ps (Fo) or 1300 ps (Fm) in the presence of Mg2+; in comparison, the mutant barley yielded a short-lived fluorescence component of approx. 50 ps and a long-lived component of 194 ps (Fo) and 424 ps (Fm). (c) The absence of the light-harvesting chlorophyll a/b-protein complex in the mutant results in a low fluorescence quantum yield which is unaffected by the cation composition of the medium. (d) The fluorescence yield changes seen in steady-state experiments on closing Photosystem II reaction centres (Fm/Fo) or on the addition of MgCl2 (+Mg2+/-Mg2+) were in overall agreement with those calculated from the time-resolved fluorescence measurements. The results suggest that the short-lived fluorescence component is partly attributable to the chlorophyll a antenna of Photosystem I, and, in part, to those light-harvesting-Photosystem II pigment combinations which are strongly coupled to the Photosystem I antenna chlorophyll. The long-lived fluorescence component can be ascribed to the light-harvesting-Photosystem II pigment combinations not coupled with the antenna of Photosystem I. In the case of the mutant, the two components appear to be the separate emissions from the Photosystem I and Photosystem II antenna chlorophylls.
皮秒时间分辨荧光光谱已被用于研究野生型大麦叶绿体以及大麦突变体chlori na f - 2叶绿体的荧光发射，该突变体缺乏捕光叶绿素a/b蛋白复合体。在Fo和Fm水平上，研究了分离叶绿体中阳离子控制的激发能分布调节。结果发现：(a) 即使在低激发强度下（小于2×10¹⁴ 光子·厘米⁻²），荧光衰减曲线也明显是非指数型的。(b) 然而，荧光衰减曲线可用双指数衰减定律描述。在Mg²⁺ 存在的情况下，野生型大麦叶绿体产生了约140皮秒的短寿命荧光成分和600皮秒（Fo）或1300皮秒（Fm）的长寿命成分；相比之下，突变型大麦产生了约50皮秒的短寿命荧光成分和194皮秒（Fo）和424皮秒（Fm）的长寿命成分。(c) 突变体中缺乏捕光叶绿素a/b蛋白复合体导致荧光量子产率较低，且不受介质阳离子组成的影响。(d) 在关闭光系统II反应中心（Fm/Fo）或添加MgCl₂（+Mg²⁺/-Mg²⁺）的稳态实验中观察到的荧光产率变化与从时间分辨荧光测量计算得到的结果总体一致。结果表明，短寿命荧光成分部分归因于光系统I的叶绿素a天线，部分归因于与光系统I天线叶绿素强烈耦合的那些捕光 - 光系统II色素组合。长寿命荧光成分可归因于未与光系统I天线耦合的捕光 - 光系统II色素组合。对于突变体，这两个成分似乎是光系统I和光系统II天线叶绿素的单独发射。
