Identification by time-resolved EPR of the peridinins directly involved in chlorophyll triplet quenching in the peridinin-chlorophyll a-protein from Amphidinium carterae
Identification by time-resolved EPR of the peridinins directly involved in chlorophyll triplet quenching in the peridinin-chlorophyll a-protein from Amphidinium carterae
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DOI：
10.1016/j.bbabio.2007.09.002
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发表时间：
2008-02-01
影响因子：
4.3
通讯作者：
Carbonera, Donatella
中科院分区：
文献类型：
--
作者：
Di Valentin, Marilena;Ceola, Stefano;Carbonera, Donatella
采用时间分辨EPR （TR-EPR）技术研究了黄鳝鞘磷脂-叶绿素-蛋白（PCP）的三重态-三重态能量传递机制。该方法利用了三重态-三重态能量传递过程中自旋守恒的概念，从而在观察到的TR-EPR光谱中产生自旋极化守恒。受体（橄榄素）以一种依赖于供体-受体对的相对几何排列的方式继承供体（叶绿素）的极化。从初始填充的叶绿素三重态出发，从PCP的x射线结构中取叶绿素和橄榄素之间的相对位置，计算出复合物中任何橄榄素的预期三重态极化。通过与实验数据的比较，我们提出了蛋白质三重态猝灭的途径。直接参与三重态-三重态能量传递的peri - in-叶绿素I对与中心到中心距离最短的对重合。一个与Chl的中心Mg原子配位的水分子也被放置在与周磷脂紧密接触的位置。这些结果支持了三重态定位的概念，即通过伪C-2对称相关的两个色素亚簇中的每一个都主要在一个特定的周内素中定位。(c) 2007 Elsevier B.V.版权所有
The mechanism of triplet-triplet energy transfer in the peridinin-chlorophyll-protein (PCP) from Amphidinium carterae was investigated by time-resolved EPR (TR-EPR). The approach exploits the concept of spin conservation during triplet-triplet energy transfer, which leads to spin polarization conservation in the observed TR-EPR spectra. The acceptor (peridinin) inherits the polarization of the donor (chlorophyll) in a way which depends on the relative geometrical arrangement of the donor-acceptor couple. Starting from the initially populated chlorophyll triplet state and taking the relative positions among Chls and peridinins from the X-ray structure of PCP, we calculated the expected triplet state polarization of any peridinin in the complex. Comparison with the experimental data allowed us to propose a path for triplet quenching in the protein. The peri din in-chlorophyl I pair directly involved in the triplet-triplet energy transfer coincides with the one having the shortest center to center distance. A water molecule, which is coordinated to the central Mg atom of the Chl, is also placed in close contact with the peridinin. The results support the concept of localization of the triplet state mainly in one specific peridinin in each of the two pigment subclusters related by a pseudo C-2 symmetry. (c) 2007 Elsevier B.V. All rights reserved.