Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
Photosynth Res. 1993 Mar;35(3):311-21. doi: 10.1007/BF00016562.
Monomeric and trimeric Photosystem I core complexes from the cyanobacterium Synechocystis PCC 6803 and LHC-I containing Photosystem I (PS I-200) complexes from spinach have been characterized by steady-state, polarized light spectroscopy at 77 K. The absorption spectra of the monomeric and trimeric core complexes from Synechocystis were remarkably similar, except for the amplitude of a spectral component at long wavelength, which was about twice as large in the trimeric complexes. This spectral component did not contribute significantly to the CD-spectrum. The (77 K) steady-state emission spectra showed prominent peaks at 724 nm (for the Synechocystis core complexes) and at 735 nm (for PS I-200). A comparison of the excitation spectra of the main emission band and the absorption spectra suggested that a significant part of the excitations do not pass the red pigments before being trapped by P-700. Polarized fluorescence excitation spectra of the monomeric and trimeric core complexes revealed a remarkably high anisotropy (∼0.3) above 705 nm. This suggested one or more of the following possibilities: 1) there is one red-most pigment to which all excitations are directed, 2) there are more red-most pigments but with (almost) parallel orientations, 3) there are more red-most pigments, but they are not connected by energy transfer. The high anisotropy above 705 nm of the trimeric complexes indicated that the long-wavelength pigments on different monomers are not connected by energy transfer. In contrary to the Synechocystis core complexes, the anisotropy spectrum of the LHC I containing complexes from spinach was not constant in the region of the long-wavelength pigments, and decreased significantly below 720 nm, the wavelength where the long-wavelength pigments on the core complexes start to absorb. These results suggested that in spinach the long-wavelength pigments on core and LHC-I are connected by energy transfer and have a non-parallel average Qy(0-0) transitions.
单体和三聚体的光合系统 I 核心复合物来自蓝藻集胞藻 PCC 6803 和含有 LHC-I 的菠菜光合系统 I（PS I-200）复合物已通过在 77 K 下的稳态、偏振光光谱学进行了表征。除了在三聚体复合物中大约两倍大的长波长光谱分量的幅度之外，集胞藻的单体和三聚体核心复合物的吸收光谱非常相似。该光谱分量对 CD 光谱没有显著贡献。（77 K）稳态发射光谱在 724nm（用于集胞藻核心复合物）和 735nm（用于 PS I-200）处显示出明显的峰。主发射带的激发光谱与吸收光谱的比较表明，在被 P-700 捕获之前，很大一部分激发不能通过红色色素。单体和三聚体核心复合物的偏振荧光激发光谱在 705nm 以上显示出非常高的各向异性（约 0.3）。这表明以下可能性之一或多种可能性：1）有一个最红色的色素，所有激发都指向该色素，2）有更多的最红色的色素，但具有（几乎）平行的取向，3）有更多的最红色的色素，但它们不是通过能量转移连接的。三聚体复合物在 705nm 以上的高各向异性表明，不同单体上的长波长色素之间没有通过能量转移连接。与集胞藻核心复合物相反，菠菜中含有 LHC-I 的复合物的各向异性光谱在长波长色素区域内不是恒定的，并且在 720nm 以下显著下降，在核心复合物上的长波长色素开始吸收的波长。这些结果表明，在菠菜中，核心和 LHC-I 上的长波长色素通过能量转移连接并且具有非平行的平均 Qy（0-0）跃迁。
