[Selective distribution and physiological function of heterogeneous carotenoids in purple photosynthetic bacterium Rhodopseudomonas palustris].
[Selective distribution and physiological function of heterogeneous carotenoids in purple photosynthetic bacterium Rhodopseudomonas palustris].
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紫色光合细菌沼泽红假单胞菌中异质类胡萝卜素的选择性分布及其生理功能
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发表时间：
2008
期刊：
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通讯作者：
Yuan Liu
中科院分区：
文献类型：
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作者：
Juan Feng;Xue;Yuan Liu
紫色光合细菌Rhodopathicum（Rps.）palustris是独特的，在外围捕光复合体（LH 2）和核心复合体（LH 1-RC）的类胡萝卜素组成的异质性。研究色素蛋白复合物中各种类胡萝卜素的选择性分布及其生理功能具有重要意义。本文采用高效液相色谱法（HPLC）分析了从萝卜中分离得到的LH 2和LH 1-RC复合物中类胡萝卜素的组成。生长在中等光照强度的沼泽。HPLC洗脱图谱的比较表明，具有11或12个共轭双键的类胡萝卜素，包括番茄红素（n = 11），脱水红色素（n = 12）和视紫红质（n = 12），是LH 2中的主要成分，而油菜黄素（n = 13）优先结合到核心复合物。通过比较LH 2和LH 1-RC的稳态吸收光谱和NIR荧光激发光谱，确定了类胡萝卜素到BChl能量转移的平均产率，所述吸收光谱和NIR荧光激发光谱在BChl Qx跃迁处归一化。结果表明，在LH 1-RC复合物中，能量转移率分别从LH 2复合物的30.9%（upper = 0）、25.4%（upper = 1）和30.4%（upper = 2）下降到LH 1-RC复合物的10.7%（upper = 0）、7.8%（upper = 1）和11.4%（upper = 2）。此外，利用亚微秒时间分辨吸收光谱研究了类胡萝卜素的三重激发态，在532 nm处的光激发下，在室温下观察到LH 1-RC和LH 2复合物在571 nm处的T（n）<- T1瞬态吸收最大值。这两个光谱分量的动力学曲线，这是分配给类胡萝卜素与n = 13和n = 12，可以很好地拟合到一个单一的指数衰减函数的表观时间常数为1.6和2.2微米，分别。上述数据表明，异质类胡萝卜素选择性地分布在LH 2和核心复合物中，其中LH 2复合物中的短共轭类胡萝卜素作为有效的辅助捕光色素，而LH 1-RC优先结合的长共轭类胡萝卜素主要执行光保护功能。
Purple photosynthetic bacterium Rhodopseudomonas (Rps.) palustris is unique in the heterogeneous carotenoid compositions in peripheral light-harvesting complex (LH2) and core complex (LH1-RC). It is of great significance to investigate selective distribution and the physiological function of various carotenoids occurring in the pigment-protein complexes mentioned above. In the present paper, high performance liquid chromatogram (HPLC) was applied to analyze the carotenoid composition in LH2 and LH1-RC complexes isolated from Rps. palustris growing in medium light intensity. Comparison of the HPLC elution profiles showed that carotenoids having 11 or 12 conjugated double bonds, including lycopene (n = 11), anhydrorhodivibrin (n = 12) and rhodopin (n = 12), were the predominant components in LH2, whereas spirilloxanthin with n = 13 was preferentially bound to core complex. The average yields of carotenoid-to-BChl energy transfer in LH2 and LH1-RC were determined by comparing their steady-state absorption spectra and NIR fluorescence excitation spectroscopy, which were normalized at the BChl Qx transition. It was found that energy transfer yield decreased from 30.9% (upsilon = 0), 25.4% (upsilon = 1) and 30.4% (upsilon = 2) in LH2 complex to 10.7% (upsilon = 0), 7.8% (upsilon = 1) and 11.4% (upsilon = 2) in LH1-RC complex, respectively. Additionally, triplet excited state carotenoids were investigated by means of sub-microsecond time-resolved absorption spectroscopy, where T(n) <-- T1 transient absorption maximum was observed at 571 nm for LH1-RC and 560 nm for LH2 complex at room temperature following the photo-excitation of carotenoid at 532 nm. The dynamic curves of these two spectral components, which were assignable to carotenoids with n = 13 and n = 12, could be well fitted to a single exponential decay function with the apparent time constants of 1.6 and 2.2 micros, respectively. The aforementioned data suggested that heterogeneous carotenoids were selectively distributed in LH2 and core complex, where short-conjugated carotenoids in LH2 complex serve as efficient accessory light-harvesting pigments, whereas long-conjugated carotenoids preferentially bound to LH1-RC mainly perform photo-protection function.