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首页> 外文期刊>Forensic science international >Factors leading to the degradation/loss of insulin in postmortem blood samples
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Factors leading to the degradation/loss of insulin in postmortem blood samples

机译：导致死后血液样本中胰岛素降解/丢失的因素

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Since lethal insulin injection has been used in murder and suicide cases, its non-ambiguous detection in postmortem, mostly hemolytic blood samples is still a problem. In the present study the stability of insulin and reasons for its loss in those blood samples were examined. When incubated with buffer, serum or with intact blood cell suspensions insulin concentrations were found to remain stable over time, but a significant loss of insulin was observed in hemolyzed blood samples. This was not due to an enzymatic cleavage, but predominantly to the presence of hemoglobin. Incubation of insulin with a hemoglobin solution containing the same hemoglobin content as hemolyzed blood caused a dramatic decrease of the insulin concentration. Degradation of insulin reached its maximum after 23 h of incubation. The charge state of the ferric ion of hemoglobin could not be held accountable for the insulin-loss, but rather the protein part of hemoglobin. Alkylation experiments using iodoacetamide suggested that the thiol groups of the globin molecule are involved in the insulin loss preventing degradation at least partially. The same was observed by lowering the pH to 2.7 in the incubation mixture. Two degradation products of insulin were identified by mass spectrometry such as modified insulin A and B chains with 4 (A chain) and 2 Da (B chain) lower masses. These results suggest that thiol groups of hemoglobin cause splitting of the disulfide bonds of insulin which immediately leads to the formation of new intramolecular disulfide bridges, a reaction which occurs in hemolytic blood and may explain the gradual loss of insulin in postmortem blood samples.
机译：由于致命注射胰岛素已用于谋杀和自杀案件，因此在死后（主要是溶血的血液样本）中进行无歧义的检测仍然是一个问题。在本研究中，检查了这些血液样本中胰岛素的稳定性及其损失的原因。当与缓冲液，血清或完整的血细胞悬液一起温育时，发现胰岛素浓度随时间推移保持稳定，但在溶血的血液样本中观察到胰岛素明显损失。这不是由于酶促裂解，而是主要由于血红蛋白的存在。胰岛素与血红蛋白含量与溶血血液含量相同的血红蛋白溶液一起孵育会导致胰岛素浓度急剧下降。孵育23小时后，胰岛素的降解达到最大。不能认为血红蛋白的铁离子的电荷状态是胰岛素损失的原因，而是血红蛋白的蛋白质部分的原因。使用碘乙酰胺的烷基化实验表明，珠蛋白分子的硫醇基团参与了胰岛素的丢失，至少部分防止了降解。通过将温育混合物中的pH降低至2.7可以观察到相同的结果。通过质谱鉴定了胰岛素的两种降解产物，例如具有4个（A链）和2个Da（B链）低质量的修饰的胰岛素A和B链。这些结果表明血红蛋白的硫醇基团导致胰岛素的二硫键断裂，这立即导致新的分子内二硫键的形成，该反应在溶血血液中发生并且可以解释死后血液样品中胰岛素的逐渐损失。

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