Csako G, Tsai C M, Slomiany B L, Herp A, Elin R J
Radiat Res. 1986 Mar;105(3):283-95.
A highly purified bacterial lipopolysaccharide (LPS) preparation was exposed in water to megadoses of ionizing radiation from a 60Co source. As evidenced by electrophoresis, the radiation treatment progressively degraded the lipopolysaccharide molecules by removing first the O-side chain units and then components of the R-core. Chemical analysis of the irradiated (LPS) preparations showed that, in accord with the structural changes, the most profound effects of ionizing radiation occurred in the hydrophilic oligo/polysaccharide moieties (R-core and O-side chain). Progressively higher doses of radiation degraded the simple sugars in decreasing order of galactose, galactosamine, glucosamine, glucose, and heptose. The R-core component 2-keto-3-deoxyoctonate was the most "resistant" sugar derivative to ionizing radiation. Due to its central position in the LPS aggregates in water, even at comparatively high doses of radiation the hydrophobic lipid A moiety of endotoxin was less affected than the sugar components. Of the fatty acids of lipid A, however, either partial conversion of beta-hydroxymyristic acid into myristic acid or selective loss of the former occurred. The observed structural and chemical changes of LPS are consistent with the effect of active oxygen radicals of radiolysis. In addition, the extensive physicochemical changes explain the altered biological reactivity of radiation-treated endotoxins.
一种高度纯化的细菌脂多糖（LPS）制剂在水中受到来自钴60源的超大剂量电离辐射。电泳结果表明，辐射处理通过首先去除O侧链单元，然后是R核心的成分，逐步降解脂多糖分子。对辐照后的（LPS）制剂进行化学分析表明，与结构变化一致，电离辐射的最显著影响发生在亲水性寡糖/多糖部分（R核心和O侧链）。逐渐增加的辐射剂量按半乳糖、半乳糖胺、葡糖胺、葡萄糖和庚糖的降序降解单糖。R核心成分2-酮-3-脱氧辛酸是对电离辐射最“耐受”的糖衍生物。由于其在水中LPS聚集体中的中心位置，即使在相对高剂量的辐射下，内毒素的疏水脂质A部分也比糖成分受影响小。然而，在脂质A的脂肪酸中，要么β-羟基肉豆蔻酸部分转化为肉豆蔻酸，要么前者选择性损失。观察到的LPS的结构和化学变化与辐射分解产生的活性氧自由基的作用一致。此外，广泛的物理化学变化解释了辐射处理后的内毒素生物反应性的改变。
