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首页> 外文期刊>Biochemistry >Femtosecond time-resolved absorption spectroscopy of main-form and high-salt peridinin-chlorophyll a-proteins at low temperatures
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Femtosecond time-resolved absorption spectroscopy of main-form and high-salt peridinin-chlorophyll a-proteins at low temperatures

机译：飞秒时间分辨的主要形式和高盐度芹菜素-叶绿素a蛋白在低温下的吸收光谱

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Steady-state and femtosecond time-resolved optical methods have been used to compare the spectroscopic features and energy transfer dynamics of two systematically different light-harvesting complexes from the dinoflagellate Amphidinium carterae: main-form (MFPCP) and high-salt (HSPCP) peridinin-chlorophyll a-proteins. Pigment analysis and X-ray diffraction structure determinations [Hofmann, E., Wrench, P. M., Sharples, F. P., Hiller, R. G., Welte, W., Diederichs, K. (1996) Science 272, 1788-1791; T. Schulte, F. P. Sharples, R. G. Hiller, and E. Hofmann, unpublished results] have revealed the composition and geometric arrangements of the protein-bound chromophores. The MFPCP contains eight peridinins and two chlorophyll (Chl) a, whereas the HSPCP has six peridinins and two Chl a, but both have very similar pigment orientations. Analysis of the absorption spectra has shown that the peridinins and Chls absorb at different wavelengths in the two complexes. Also, in the HSPCP complex, the Q(y) transitions of the Chls are split into two well-resolved bands. Quantum computations by modified neglect of differential overlap with partial single and double configuration interaction (MNDO-PSDCI) methods have revealed that charged amino acid residues within 8 angstrom of the pigment molecules are responsible for the observed spectral shifts. Femtosecond time-resolved optical spectroscopic kinetic data from both complexes show ultrafast (< 130 fs) and slower (similar to 2 ps) pathways for energy transfer from the peridinin excited singlet states to Chl. The Chl-to-Chl energy transfer rate constant for both complexes was measured and is discussed in terms of the Forster mechanism. It was found that, upon direct Chl excitation, the Chl-to-Chl energy transfer rate constant for MFPCP was a factor of 4.2 larger than for HSPCP. It is suggested that this difference arises from a combination of factors including distance between Chls, spectral overlap, and the presence of two additional peridinins in MFPCP that act as polarizable units enhancing the rate of Chl-to-Chl energy transfer. The study has revealed specific pigment-protein interactions that control the spectroscopic features and energy transfer dynamics of these light-harvesting complexes.
机译：稳态和飞秒时间分辨光学方法已被用于比较来自鞭毛鞭毛藻的两种系统上不同的光收集复合物的光谱特征和能量转移动力学：主形（MFPCP）和高盐（HSPCP）的维他命宁-叶绿素a蛋白。颜料分析和X射线衍射结构测定[Hofmann，E.，Wrench，P.M。，Sharples，F.P.，Hiller，R.G.，Welte，W.，Diederichs，K。（1996）Science 272，1788-1791; Professional 272，1788-1791。 T. Schulte，F.P。Sharples，R.G。Hiller和E.Hofmann，[未发表的结果]揭示了结合蛋白的发色团的组成和几何排列。 MFPCP含有8个Peridinin和2个叶绿素（Chl）a，而HSPCP有6个Peridinin和2个Chl a，但两者的颜料取向非常相似。吸收光谱的分析表明，苦瓜素和Chls在两种络合物中以不同的波长吸收。同样，在HSPCP复合物中，Chls的Q（y）跃迁被分为两个良好分辨的谱带。通过修正忽略差异重叠与部分单配置和双配置相互作用（MNDO-PSDCI）方法进行的量子计算显示，颜料分子8埃内的带电氨基酸残基负责观察到的光谱偏移。飞秒时间分辨的光谱动力学数据来自这两种配合物，显示了从peridinin激发的单重态到Chl的能量转移的超快（<130 fs）和慢（类似于2 ps）途径。测量了两种配合物的Ch1到Chl能量转移速率常数，并根据Forster机理进行了讨论。已经发现，在直接的Ch1激发下，MFPCP的Ch1-Chl能量传递速率常数比HSPCP大4.2倍。有人认为，这种差异是由多种因素共同引起的，包括Chl之间的距离，光谱重叠以及MFPCP中两个额外的苦抗素的存在，它们是可极化的单位，可增强Chl到Chl的能量转移速率。这项研究揭示了特定的色素-蛋白质相互作用，这些相互作用控制着这些光收集复合物的光谱特征和能量转移动力学。

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