Seely G R, Rehms A A
Department of Chemistry, Arizona State University, Tempe 85287-1604.
Photochem Photobiol. 1992 Feb;55(2):257-66. doi: 10.1111/j.1751-1097.1992.tb04235.x.
In the presence of a surfactant that does not ligate Mg, chlorophyll is adsorbed to polyethylene particles swollen with tetradecane principally as the infrared-absorbing, highly polymeric species Chl 740. Examples of such surfactants are quaternary ammonium salts and soaps. However, when surfactants of opposite charge are present together, in this case dodecylpyridinium iodide and Na butyrate or myristate, chlorophyll may exist entirely in a dispersed form absorbing around 666 nm. Absorption and fluorescence spectral data show that much of the dispersed pigment is still associated, but as dimeric and perhaps short oligomeric species. It is concluded from fluorescence lifetime analysis that most of the observed fluorescence comes from a small population of chlorophyll that is probably monomeric and isolated; fluorescence of more highly associated species decays with a wide range of lifetimes. The capacity for photochemical sensitization of these particles with dispersed chlorophyll is similar to that of particles with ligating surfactants examined earlier. Structures are suggested for chlorophyll association in which Mg is ligated by water hydrogen-bonded to a carboxylate group, while the dodecylpyridinium counterion lies near the chlorophyll ring. The effect of the two surfactants is synergistic. Overall, spectra of dispersed chlorophyll adsorbates resemble most closely those of colloidal chlorophyll suspensions prepared by dilution of solutions in polar organic solvents with water.
在存在不与镁结合的表面活性剂的情况下，叶绿素主要以吸收红外线的高聚物种叶绿素740吸附到用十四烷溶胀的聚乙烯颗粒上。这类表面活性剂的例子有季铵盐和肥皂。然而，当带相反电荷的表面活性剂同时存在时，在这种情况下为十二烷基碘化吡啶鎓和丁酸钠或肉豆蔻酸钠，叶绿素可能完全以吸收约666nm波长光的分散形式存在。吸收光谱和荧光光谱数据表明，大部分分散的色素仍然是缔合的，但以二聚体形式存在，或许还有短链低聚体形式。通过荧光寿命分析得出的结论是，观察到的大部分荧光来自一小部分可能为单体且孤立的叶绿素；缔合程度更高的物种的荧光以宽范围的寿命衰减。这些含有分散叶绿素的颗粒的光化学敏化能力与早期研究的含有结合表面活性剂的颗粒相似。有人提出了叶绿素缔合的结构，其中镁通过与羧酸盐基团氢键结合的水进行配位，而十二烷基吡啶鎓抗衡离子位于叶绿素环附近。两种表面活性剂的作用是协同的。总体而言，分散叶绿素吸附物的光谱与通过用水稀释极性有机溶剂中的溶液制备的胶体叶绿素悬浮液的光谱最为相似。
