Polarized fluorescence of aggregated bacteriochlorophyll c and baseplate bacteriochlorophyll a in single chlorosomes isolated from Chloroflexus aurantiacus.
Polarized fluorescence of aggregated bacteriochlorophyll c and baseplate bacteriochlorophyll a in single chlorosomes isolated from Chloroflexus aurantiacus.
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DOI：
10.1021/bi0623072
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发表时间：
2007-05
期刊：
影响因子：
2.9
通讯作者：
Y. Shibata;Y. Saga;H. Tamiaki;S. Itoh
中科院分区：
文献类型：
--
作者：
Y. Shibata;Y. Saga;H. Tamiaki;S. Itoh
使用共焦激光显微镜在 13 K 下测量从绿色丝状细菌 Chloroflexus aurantiacus 中分离出的单个叶绿体的荧光偏振各向异性。漂浮在冷冻溶剂中的每个单个叶绿体都表现出强烈的荧光偏振各向异性。我们计算了 51 个浮动单叶绿体的荧光偏振度。对于核心叶绿体中的 BChl-c 聚集体，该值的范围为 0.1 至 0.76；对于外膜底板蛋白中的能量受体 BChl-a，该值的范围为 0 至 0.4。两个发射带之间的偏振角变化分布在所有可能的值上，在 90 度左右有一个尖锐的峰值，表明 BChl-c 聚集体和 BChl-a 荧光发射的过渡偶极子之间的垂直方向。假设叶绿体随机方向的模拟准确地再现了实验结果。分析进一步表明 BChl-c 的过渡偶极子的显着贡献，其方向垂直于每个叶绿体的主极化轴。较小的偏振度值意味着 BChl-a 跃迁偶极子相对于叶绿体所附着的细胞质膜的法向有些倾斜。这些结论只能通过观察单个叶绿体的荧光来获得。
The polarization anisotropy of fluorescence from single chlorosomes isolated from a green filamentous bacterium, Chloroflexus aurantiacus, was measured using a confocal laser microscope at 13 K. Each single chlorosome that is floating in a frozen solvent exhibited strong polarization anisotropy of fluorescence. We calculated the degrees of fluorescence polarization for 51 floating single chlorosomes. The value ranged from 0.1 to 0.76 for the BChl-c aggregate in the core chlorosomes and from 0 to 0.4 for the energy acceptor BChl-a in the baseplate protein in the outer membrane. The shifts in polarization angles between the two emission bands were distributed over all the possible values with a sharp peak around 90 degrees , suggesting the perpendicular orientation between the transition dipoles of the fluorescence emission from the BChl-c aggregate and that from BChl-a. A simulation assuming a random orientation of chlorosomes reproduced the experimental results exactly. The analysis further indicated the appreciable contribution of the transition dipole of BChl-c that has an orientation perpendicular to the major polarization axis in each chlorosome. Small values of the degrees of polarization implied the BChl-a transition dipole to be somewhat tilted with respect to the normal of the cytoplasmic membrane to which chlorosomes are attached. These conclusions can be obtained only by observing the fluorescence of single chlorosomes.