The flow of excitation energy in LHCII monomers:: Implications for the structural model of the major plant antenna
The flow of excitation energy in LHCII monomers:: Implications for the structural model of the major plant antenna
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DOI：
10.1016/s0006-3495(98)77747-1
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发表时间：
1998-12-01
影响因子：
3.4
通讯作者：
van Amerongen, H
中科院分区：
文献类型：
--
作者：
Gradinaru, CC;Özdemir, S;van Amerongen, H
通过选择性激发（663、669、672、678和682 nm）不同Chl a吸收带，并检测整个Q（y）区域（650 - 700 nm）的诱导变化，从亚皮秒瞬态吸收研究中获得了捕光复合物II（LHCII）单体内能量转移的光谱和动力学信息。结果表明，在5 +/-1ps的时间内，从663 nm附近吸收的色素到低能色素的转移发生，而670 nm激发分两个阶段传递到同一“目的地（0.30 +/- 0.05 ps和12 +/- 2 ps），并且在主吸收带（675-680 nm）内发生快速平衡（寿命0.45 +/- 0.05 ps）。通过与三聚体样品的类似时间分辨测量结果进行比较，可以得出结论，单体内能量转移完全决定了在天然LHCII复合物中观察到的光谱平衡。为了将测量的寿命及其相关光谱与LHCII的可用结构模型内的颜料组织相关联（Kuhlbrandt et.等，1994年。自然367：614-621），使用了广泛但直接的理论建模。因此，Kuhlbrandt及其同事给出的色素归属（Chl a或Chl B）不能同时描述相当同源的LHCII和CP 29蛋白质的二色性光谱和瞬时吸收结果。CP 29的一个更近的分配，其中Chl B分子（“Chl b5”）被鉴定为Chl a（R. Bassi，personal communication），导致了对CP 29和LHCII的更好描述。此外，跃迁偶极矩的取向，这还没有得到在晶体结构中，现在被分配为大部分的叶绿素的。
Spectral and kinetic information on energy transfer within the light-harvesting complex II (LHCII) monomer was obtained from this subpicosecond transient absorption study, by using selective excitation (663, 669, 672, 678, and 682 nm) of various Chl a absorption bands and detecting the induced changes over the entire Q(y) region (650 -700 nm). It is shown that transfer from the pigment(s) absorbing around 663 nm to the low energy ones occurs in 5 +/- 1 ps, whereas the 670-nm excitation is delivered to the same "destination" in two phases (0.30 +/- 0.05 ps, and 12 +/- 2 ps) and a fast equilibration (lifetime 0.45 +/- 0.05 ps) takes place within the main absorption band (675-680 nm). From comparison with results from similar time-resolved measurements on trimeric samples, it can be concluded that the intramonomeric energy transfer completely determines the spectral equilibration observed in native LHCII complexes. To correlate the measured lifetimes and their associated spectra with the pigment organization within the available structural model of LHCII (Kuhlbrandt et. al. 1994. Nature. 367:614-621), extensive but straightforward theoretical modeling was used. Thus it is demonstrated that the pigment assignment (Chl a or Chl b) given by Kuhlbrandt and co-workers cannot simultaneously describe the dichroic spectra and the transient absorption results for the rather homologous LHCII and CP29 proteins. A more recent assignment for CP29, in which a Chl b molecule ("Chl b5") is identified as a Chl a (Dr. R. Bassi, personal communication), leads to a much better description of both CP29 and LHCII. Furthermore, the orientations of the transition dipole moments, which have not been obtained in the crystal structure, are now assigned for most of the Chl's.