假根羽藻外周天线三聚体超快荧光动力学研究

通过对稳态、瞬态吸收谱以及瞬态荧光发射谱的测量分析得出：在三聚体内存在以下六个特征叶绿素分子Chl b628、Chl b646、Chl b654,657652、Chl a666664、Chl a677,680674、Chl a683682(下标为吸收峰,上标为发射峰).在波长为655 nm、666 nm、680 nm、683 nm时分别采用时间相干单光子技术(TCSPC)记录其荧光动力学谱.根据荧光产生的物理学机制,对这些荧光动力学谱的分析采用的是分子同时接受能量与耗散能量的指数模型,得出在离体的外周天线三聚体内,Chl b654,657652、Chl a666664、Chl a677,680674和Chla683682分子在接受Chlb628分子的传能时,大部分经过了Chlb646分子,传能时间发生在97~157ps的时间间隔内,可见Chlb646分子在外周天线三聚体中是连接Chlb和Chla传能的主要分子;Chl b654,657652…→Chl a666664…→Chl a677,680674…→Chl a683682分子依次传能的时间在10 ps左右,这种传递过程可归结为是处于激发态分子首先经过内转换后再将能量以Frster共振机制的形式传给了其它分子;大量小于1 ps 的传能过程是叶绿素分子之间以激子共振的方式进行直接传能;Chl b654,657652、Chl a666664、Chl a677,680674和Chl a683682分子以时间常量分别为1.44 ns, 1.43 ns, 636 ps, 713 ps发射荧光回到基态.

Ultrafast Dynamics Study of Fluorescence in Trimeric Light-Harvesting Complex II of Bryopsis Corticulans

An ultrafast dynamics study of fluorescence in LHCⅡ on energy transfer among chlorophyll in a trimeric unit of major light-harvesting complex (LHCⅡ) from bryopsis corriculan were conducted by technique of Time Correlated Single Photon Counting (TCSPC).Six characteristic molecules marked asChl b628、Chl b646、Chl b654,657652、Chl a666664、Chl a677,680674、Chl a683682 were discriminated in the chlorophyll Q region of LHC II by transient absorption spectrum and fluorescence emission spectrum.According to the principle of fluorescence kinetics, these kinetics data recorded by TCSPC were analyzed with a multi-exponential model. Time constants on energy transfer and decay of excitations were obtained as:Overwhelming parts of the energy transfer among chlorophylls under a long process than 97 ps:Chl b628…→Chl b646…→Chl b654,657652(149 ps),Chl b628…→Chl b646…→Chl b666664(157 ps),Chl b628…→Chl b646…→Chl a677,680674(103 ps) and Chl b628…→Chl b646…→Chl a683682(97 ps) which denotes that Chl b646is the main moleculars that transfer energy from Chlbs to Chlas. Some slower process of energy transfer such as Chl b654,657652…14.5 psChl a683682,Chl a666664…8.1 psChl a683682,Chl a677,680674…9.3 psChl a683682 were also obtained.The pathway can be described as that the excited Chls goes through internal conversion before transferring energy to another Chls.Although with higher standard deviation, time constants in femtosecond level can be attributed to the process of directly energy transfer,such as C628→C654,657652,C628→C666664,C628→C677,680674,C628→C683682,C654,657652→C666664,C628→C654,657652→C666664,C628→C654,657652→C677,680674.Owing to the arrangement and direction of dipole moment of Chls in LHCⅡ,the probability of these processes is different.The fluorescence lifetimes of Chl b654,657652,Chl a666664,Chl a677,680674 and Chl a683682 were determined to be 1.44 ns,1.43 ns,636 ps,713 ps respectively.The percentages of energy dissipation in the pathway of fluorescence emission are no more than 40% in the trimeric unit of LHCⅡ.