Department of Applied Chemistry, College of Engineering, University of Osaka Prefecture, Gakuencho, 593, Sakai, Japan.
Photosynth Res. 1994 Jul;41(1):235-43. doi: 10.1007/BF02184164.
Artificial aggregates of bacteriochlorophyllc (BChlc) were formed in an aqueous medium in the presence of a lipid, monogalactosyl diglyceride (MGDG), and the optical properties of those aggregates were studied by absorption and circular dichroism (CD) mainly. Four BChlc homologs, ([E,E]BChlc F, [P,E]BChlc F, [E,M]BChlc F and [I,E]BChlc F), were isolated from the green photosynthetic bacteriumChlorobium limicola strain 6230. Above 0.0004%, MGDG induced a red-shift of the absorption maxima of BChlc aggregates. At 0.003% MGDG BChlc aggregates showed absorption maxima in the range of 724 to 745 (±3) nm with a shift of 12 to 24 (±3) nm depending on the homolog species. Four kinds of BChlc-MGDG aggregates showed characteristic CD spectra. [E,M]BChlc F gave rise to a CD spectrum similar to that of chlorosomes, while the other three gave spectra of opposite sign. These aggregates are sensitive to 1-hexanol treatment; in a saturating amount (0.85%) of 1-hexanol, all the homologs gave a monomer-like absorption spectrum peaking at 670nm. At an intermediate concentration (0.5%), [E,M]BChlc F showed an enhanced CD intensity, as observed in native chlorosomes. Resonance Raman spectra of the monomer-like BChlc samples indicated that the keto vibrational band at ca. 1640 cm(-1) was considerably weakened by the 0.85% 1-hexanol treatment, however the 1680 cm(-1) band characteristic of a free keto group did not appear. These results indicate that the artificial aggregates formed by purified BChlc homologs and MGDG are good models for studying chlorosomes structure.
人工细菌叶绿素 c（BChlc）聚集体在水介质中形成，存在脂质单半乳糖二甘油酯（MGDG），并通过吸收和圆二色性（CD）主要研究这些聚集体的光学性质。四种 BChlc 同系物（[E，E]BChlc F、[P，E]BChlc F、[E，M]BChlc F 和[I，E]BChlc F）从绿光合细菌 Chlorobium limicola 菌株 6230 中分离出来。MGDG 浓度高于 0.0004%时，会引起 BChlc 聚集体吸收最大值的红移。在 0.003%MGDG 下，BChlc 聚集体的吸收最大值在 724 到 745（±3）nm 范围内，根据同系物的种类，位移为 12 到 24（±3）nm。四种 BChlc-MGDG 聚集体表现出特征性的 CD 光谱。[E，M]BChlc F 产生类似于类菌胞体的 CD 光谱，而其他三种产生相反符号的光谱。这些聚集体对 1-己醇处理敏感；在 1-己醇的饱和量（0.85%）下，所有同系物均给出在 670nm 处峰值的单体样吸收光谱。在中间浓度（0.5%）下，[E，M]BChlc F 显示出增强的 CD 强度，如在天然类菌胞体中观察到的那样。单体样 BChlc 样品的共振拉曼光谱表明，在 1640cm（-1）左右的酮振动带在 0.85%1-己醇处理下大大减弱，但没有出现特征于游离酮基的 1680cm（-1）带。这些结果表明，由纯化的 BChlc 同系物和 MGDG 形成的人工聚集体是研究类菌胞体结构的良好模型。
