Laboratoire de Chimie Physique, CNRS UMR 8601, Université Paris Descartes, 45 rue des Saints Pères, 75270 Paris cedex 06, France.
Biochimie. 2010 Sep;92(9):1130-7. doi: 10.1016/j.biochi.2010.05.017. Epub 2010 Jun 4.
An investigation of radiation-induced oxidation of aqueous bovine serum albumin (BSA) in the presence of linoleate (LH) at pH 10.5 has been carried out in order to better understand the respective oxidative processes involved in both lipid and protein phases. Solutions containing BSA (15 micromol L(-1)) and linoleate (15-600 micromol L(-1)) below the critical micellar concentration (cmc=2000 micromol L(-1)), have been irradiated by gamma-rays (137Cs) at radiation doses ranging from 10 to 400 Gy (dose rate 9.5 Gy min(-1)). It can be noticed that, in the absence of BSA, the main hydroperoxides formed from HO*-induced linoleate oxidation below the cmc, do not exhibit a conjugated dienic structure. This was also verified in the presence of BSA. Selected chemical markers of oxidation have been monitored: non-conjugated dienic hydroperoxides and conjugated dienes (without hydroperoxide function) for linoleate oxidation, and carbonyl groups for BSA oxidation. We have shown that for the lowest linoleate concentration (15 micromol L(-1)) in the presence of BSA (15 micromol L(-1)), the formation of conjugated dienes was not observed, meaning that LH was not exposed to HO* radicals attack. However, non-conjugated dienic lipid hydroperoxides were simultaneously detected, indicating that LH was secondarily oxidised by BSA oxidised species. Moreover, the oxidation of linoleate was found to be enhanced by the presence of BSA. For the highest linoleate concentration (600 micromol L(-1)), the expected protection of BSA by LH was not observed, even if LH monomers were responsible for the total scavenging of HO* radicals. In this latter case, the formation of non-conjugated dienic lipid hydroperoxides was lower than expected. Those results showed that BSA was not oxidised by the direct action of HO* radicals but was undergoing a secondary oxidation by non-dienic lipid hydroperoxides and/or lipid radical intermediates, coming from the HO*-induced linoleate oxidation.
在 pH 值为 10.5 的条件下，研究了牛血清白蛋白（BSA）在亚油酸（LH）存在下的辐射诱导氧化作用，以便更好地理解脂质相和蛋白质相所涉及的各自氧化过程。BSA（15 μmol/L）和亚油酸（15-600 μmol/L）在低于临界胶束浓度（cmc=2000 μmol/L）的溶液中，用γ射线（137Cs）照射，辐射剂量范围为 10 至 400 Gy（剂量率为 9.5 Gy/min）。可以注意到，在不存在 BSA 的情况下，cmc 以下 HO*-诱导的亚油酸氧化形成的主要氢过氧化物，不具有共轭二烯结构。在存在 BSA 的情况下也得到了验证。监测了氧化的选定化学标志物：亚油酸氧化中非共轭二烯氢过氧化物和共轭二烯（无氢过氧化物功能），以及 BSA 氧化的羰基。我们表明，对于存在 BSA（15 μmol/L）时的最低亚油酸浓度（15 μmol/L），未观察到共轭二烯的形成，这意味着 LH 未受到 HO自由基的攻击。然而，同时检测到非共轭二烯脂氢过氧化物，表明 LH 被 BSA 氧化产物二次氧化。此外，发现亚油酸的氧化作用因 BSA 的存在而增强。对于最高亚油酸浓度（600 μmol/L），即使 LH 单体负责 HO自由基的总清除，也未观察到 BSA 对 LH 的预期保护。在后一种情况下，非共轭二烯脂氢过氧化物的形成低于预期。这些结果表明，BSA 不是通过 HO自由基的直接作用而氧化，而是通过非二烯脂氢过氧化物和/或来自 HO-诱导的亚油酸氧化的脂自由基中间体进行二次氧化。
