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Effects of different aggregation forms of LHC II from Bryopsis corticulans on the excited state properties of Chl a

机译:皮质双胞胎LHC II不同聚集形式对Chla激发态特性的影响

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Steady-state and time-resolved fluorescence spectroscopies have been used to study the excited state properties of Chl a in different aggregation forms of light-harvesting complex II (LHC II) from an intertidal green alga, Bryopsis corticulans, i.e. LHC II monomer, trimer and oligomer. When either Chl a or Chl b was selectively excited, the observed decrease in Chl a fluorescence in the oligomer is proved to be caused mainly by the fast fluorescence quenching among Chl a molecules, rather than by the decrease in Chl b-to-Chl a singlet excitation transfer efficiency. Analyses of the picosecond time-resolved fluorescence kinetics identified two exponential decay components in all of the three forms of LHC II: a longer-lived component (4.1 - 4.7 ns) originating from fluorescence emission of Chl a, and a shorter-lived one (135 - 540 ps) from the rapid equilibration of singlet excitation among Chl a molecules. The time constant of excitation equilibration is 135 ps in oligomer, 520 ps in trimer and 540 ps in monomer. These results imply that LHC II in oligomer form is inherently able to quench Chl a excitation, a mechanism which may be related to the photoprotection of PS II via changing the degree of LHC II aggregation in Bryopsis corticulans.
机译:稳态和时间分辨荧光光谱法已被用于研究潮间带绿藻Bryopsis corticulans(即LHC II单体,三聚体)在不同聚集形式的光捕获复合体II(LHC II)的不同形式的Chla的激发态性质。和低聚物。当Chl a或Chl b均被选择性激发时,低聚物中Chl a荧光的观察到的减少被证明主要是由于Chl a分子之间快速的荧光猝灭引起的,而不是由Chl b-to-Chl a的减少引起的单重态激发转移效率。皮秒时间分辨的荧光动力学分析确定了LHC II的所有三种形式中的两个指数衰减成分:寿命较长的成分(4.1-4.7 ns)来自Chla的荧光发射,寿命较短的( Chl a分子之间的单线态激发快速平衡得到了135-540 ps)的响应。激发平衡的时间常数在低聚物中为135 ps,在三聚体中为520 ps,在单体中为540 ps。这些结果暗示低聚物形式的LHC II固有地能够猝灭Chl激发,该机制可能与通过改变皮质隐球菌中LHC II聚集的程度与PS II的光保护有关。

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