Galanos C, Lüderitz O
Eur J Biochem. 1975 Jun;54(2):603-10. doi: 10.1111/j.1432-1033.1975.tb04172.x.
Ions of low molecular weight like metal cations and basic amines are present in lipopolysaccharides regardless of the isolation procedure employed. They are present in salt form with the acidic groups of the molecule and, partly, bound by chelation. Electrodialysis which removed a large proportion of these basic materials led to acidic lipopolysaccharides often with reduced solubility. Electrodialyzed lopopolysaccharides could be rendered soluble by neutralizing with alkali or with a basic amine. Depending on the base employed for neutralization preparations were obtained which showed in water distinct differences in solubility, viscosity and opalescence. These differences were related to differences in the sedimentation coefficients of the various salt forms. Neutralization with triethylamine led in all cases to highly soluble preparations with low sedimentation coefficients, while, on the other hand, neutralization with Mg(OH)2 led in most cases to insoluble preparations. The acidic lipopolysaccharides obtained by electrodialysis deteriorate on storing in a freeze-dried form. On heating in distilled water autohydrolysis occurs and free lipid A is liberated. The lipid A which is so far known as a water-insoluble material showed increased solubility when prepared from electrodialyzed lipopolysaccharides.
无论采用何种分离方法，脂多糖中都存在金属阳离子和碱性胺等低分子量离子。它们以盐的形式与分子中的酸性基团结合，部分通过螯合作用结合。去除大部分这些碱性物质的电渗析导致酸性脂多糖，其溶解度通常降低。通过用碱或碱性胺中和可使电渗析的脂多糖变得可溶。根据用于中和的碱的不同，得到的制剂在水中的溶解度、粘度和乳光方面表现出明显差异。这些差异与各种盐形式的沉降系数差异有关。用三乙胺中和在所有情况下都导致具有低沉降系数的高溶性制剂，而另一方面，用Mg(OH)₂中和在大多数情况下导致不溶性制剂。通过电渗析获得的酸性脂多糖以冻干形式储存时会变质。在蒸馏水中加热会发生自水解并释放出游离脂质A。迄今为止已知为水不溶性物质的脂质A，由电渗析脂多糖制备时溶解度增加。
