Trapping of a cross-link formed by a major purine adduct of a metabolite of the carcinogen N-nitrosomorpholine by inorganic and biological reductants.
Trapping of a cross-link formed by a major purine adduct of a metabolite of the carcinogen N-nitrosomorpholine by inorganic and biological reductants.
复制标题
通过无机和生物还原剂捕获致癌物 N-亚硝基吗啉代谢物的主要嘌呤加合物形成的交联。
DOI：
10.1021/tx3005289
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发表时间：
2013
影响因子：
4.1
通讯作者：
Fishbein,JamesC
中科院分区：
文献类型：
--
作者：
Koissi,Niangoran;Fishbein,JamesC
在有小牛胸腺脱氧核糖核酸存在的缓冲水溶液中，3-羟基-N-亚硝基吗啉被磷化氢还原剂处理，生成瞬时的α-羟基亚硝胺和随后的重氮离子，使脱氧核糖核酸烷化。随后加入氢化物供体30分钟，然后对混合物进行酸解，可以检测和定量6-(2-{2-[(9H-purin-6-yl)amino]ethoxy}ethoxy)-9H-purin-2-amine，。通过重氮离子在O6-Gua上沉积3-氧并戊醛碎片，并与N6-Ade缩合，可能在附近形成还原的交联键。降低反应混合物的温度和降低pH值可以适度提高捕获的交联剂的产率。在三种硼氢化物还原剂中，NaNCBH3优于NaBH4或Na(∼)3BH，在摩尔数上比NaBH4或Na(ACO)3BH高4倍。对于NaNCBH3的捕获，推测反应可能发生在与其共轭碱亚胺处于质子平衡的亚胺离子上。在分解过氧化氢并在不同时间后引入NaNCBH3的实验中，观察到交联量在一周内几乎线性增加，∼增加了4倍。这些数据表明，至少有两种交叉链接，一种是在几分钟内迅速形成的，另一种是随着时间的推移而增长的，需要几天时间。观察到烟酰胺辅因子和抗坏血酸的减少影响了交联链的减少(超过3天)，证实了本来可逆的交联链在生物条件下可能不朽的可能性。
3-Hydroperoxy-N-nitrosomorpholine in buffered aqueous media in the presence of calf thymus DNA was treated with a phosphine reductant to generate the transient α-hydroxynitrosamine and subsequent diazonium ion that alkylated the DNA, as previously reported. Subsequent addition of hydride donors, for 30 min, followed by acid hydrolysis of the mixture allowed detection and quantification of 6-(2-{2-[(9H-purin-6-yl)amino]ethoxy}ethoxy)-9H-purin-2-amine, the reduced cross-link formed from deposition, via the diazonium ion, of a 3-oxapentanal fragment on O6-Gua, and condensation with N6-Ade, presumably in the vicinity. Decreasing the temperature of the reaction mixtures and decreasing the pH modestly increased the yields of the trapped cross-link. Among three borohydride reductants, NaNCBH3is superior, being ∼4 times more effective on a molar basis, as opposed to a hydride equivalent basis, than NaBH4or Na(AcO)3BH. For trapping with NaNCBH3, it is deduced that the reaction likely occurs with the iminium ion that is in protonic equilibrium with its conjugate base imine. In an experiment in which the hydroperoxide was decomposed and NaNCBH3was introduced after various periods of time, the amount of cross-link was observed to increase, nearly linearly, by ∼4-fold over 1 week. These data indicate that there are a minimum of two populations of cross-links, one that forms rapidly, in minutes, and another that grows in with time, over days. Reduced nicotinamide cofactors and ascorbate are observed to effect reduction (over 3 days) of the cross-links, confirming the possibility that otherwise reversible cross-links might be immortalized under biological conditions.