Oligomers of bacteriochlorophyll and bacteriopheophytin with spectroscopic properties resembling those found in photosynthetic bacteria
Oligomers of bacteriochlorophyll and bacteriopheophytin with spectroscopic properties resembling those found in photosynthetic bacteria
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细菌叶绿素和细菌脱镁叶绿素的低聚物，其光谱特性类似于光合细菌中发现的光谱特性
DOI：
10.1016/0005-2728(84)90127-0
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
W. W. Parson
中科院分区：
文献类型：
--
作者：
A. Scherz;W. W. Parson
在水-有机混合溶剂体系和十二烷基二甲基氧化胺（LDAO）胶束体系中，细菌脱镁叶绿素（BPh）和细菌叶绿素（BChl）形成了寡聚体。条件被发现，得到相对均匀的样品的低聚物，并允许定量比较的单体和低聚颜料的光谱特性。某些类型的低聚物的形成伴随着BChl或BPh的长波长（Qy）吸收带的大的红移，以及其偶极强度的大幅增加（增色）。Qy带的增色现象是以损失偶极强度的Soret带为代价的。Qx波段略微向较短波长移动，并且也失去了偶极强度。在近红外（Qy）区域的CD光谱变得明显非保守。(The Qy区域的净旋转强度为正。）这也是以较短波长的带为代价发生的，其获得净负旋转强度。的低聚物的光谱特性类似于光合细菌中发现的一些BChl-蛋白质复合物。在LDAO胶束中的BPh的低聚与包含105 LDAO分子的大的圆柱形胶束的形成有关。然而，光谱的变化可能发生在小的低聚物的BPh的形成，他们开始被视为当胶束含有约10个分子的BPh。在LDAO胶束中形成的BPh低聚物在865 nm处发荧光，但相对于单体BPh的荧光产率降低约40倍。荧光产率对BPh/LDAO摩尔比不敏感，表明在这些条件下形成的低聚物主要是二聚体。当低聚物被短暂的闪光激发时，它们以低量子产率转化为亚稳态形式。这种转化可能涉及寡聚体几何结构的改变，但不是完全解离。
Oligomers of bacteriopheophytin (BPh) and bacteriochlorophyll (BChl) were formed in mixed aqueous-organic solvent systems, and in aqueous micelles of the detergent lauryldimethylamine oxide (LDAO). Conditions were found that gave relatively homogeneous samples of oligomers and that allowed quantitative comparisons of the spectroscopic properties of the monomeric and oligomeric pigments. The formation of certain types of oligomers is accompanied by a large bathochromic shift of the long-wavelength (Qy) absorption band of the BChl or BPh, and by a substantial increase in its dipole strength (hyperchromism). The hyperchromism of the Qyband occurs at the expense of the Soret band, which loses dipole strength. The Qxband shifts slightly to shorter wavelengths and also loses dipole strength. The CD spectrum in the near-infra-red (Qy) region becomes markedly nonconservative. (The net rotational strength in the Qyregion is positive.) This also occurs at the expense of the bands at shorter wavelengths, which gain a net negative rotational strength. The spectroscopic properties of the oligomers resemble those of some of the BChl-protein complexes found in photosynthetic bacteria. The oligomerization of BPh in LDAO micelles is linked to the formation of large, cylindrical micelles that contain on the order of 105LDAO molecules. However, the spectral changes probably occur on the formation of small oligomers of BPh; they begin to be seen when the micelles contain about 10 molecules of BPh. The BPh oligomers formed in LDAO micelles fluoresce at 865 nm, but the fluorescence yield is decreased about 40-fold, relative to that of monomeric BPh. The fluorescence yield is insensitive to the BPh/LDAO molar ratio, suggesting that the oligomers formed under these conditions are predominantly dimers. When the oligomers are excited with a short flash of light, they are converted with a low quantum yield into a metastable form. This transformation probably involves alterations in the geometry of the oligomer, but not full dissociation.