2-NITROSOAMINO-3-METHYLIMIDAZO[4,5-F]QUINOLINE STABILITY AND REACTIVITY

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 N-亚硝胺和亚硝胺可引发癌症。这些研究评价了2-亚硝基氨基-3-甲基咪唑[4，5-f]喹啉（N-NO-IQ）的稳定性和反应性，以评估其在2-氨基-3-甲基咪唑[4，5-f]喹啉（IQ）引发结肠癌中的可能作用。在存在和不存在亲核试剂的情况下，将14 C-N-NO-IQ与不同溶剂和pH一起孵育，并通过HPLC进行分析。通过电喷雾电离质谱法鉴别的产物包括2-氯-3-甲基咪唑[4，5-f]喹啉（2-Cl-IQ）、2，2 '-偶氮-3，3'-二甲基咪唑[4，5-f]喹啉（AZO-IQ）、2-叠氮基-IQ（2-N3-IQ）、3-甲基咪唑[4，5-f]喹啉（脱氨基-IQ）和IQ。用0.1 N HCl测试各种有机溶剂。在所有溶剂酸化后形成2-Cl-IQ和IQ。AZO-IQ仅在甲醇中形成。除甲醇外，脱氨基-IQ是所有测试醇中形成的主要产物。在5 min内完全转化N-NO-IQ的酸性条件下（含0.1 N HCl的乙腈），如果用二甲亚砜代替乙腈，30 min后仍有62%的N-NO-IQ残留。N-NO-IQ在5.5-9.0的生理pH范围内是稳定的，并且在pH7.4和37 ℃下在4小时内不与亲核试剂反应。在酸性pH（pH2.0）和37 ℃下30分钟，N-NO-IQ变得不稳定，形成亲电体，其与生物学相关的亲核体联合收割机结合。N-NO-IQ反应在pH 2.0时遵循一级动力学（t1/2 = 10 <$2 min），在10 mM NaN 3中反应显著增加（t1/2 = 2 <$0.1 min）。2-N3-IQ是在后一孵育中观察到的主要产物。N-NO-IQ在pH 2.0时与DNA的结合是pH 7.4时的100倍。在pH 2.0时，大于90%的结合被10 mM NaN 3抑制。因此，N-NO-IQ在酸性pH下形成结合DNA的反应性亲电体。N-NO-IQ反应产物可取决于细胞或组织的pH和疏水环境。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. N-Nitrosamines and nitrosamides can initiate cancer. These studies evaluated the stability and reactivity of 2-nitrosoamino-3-methylimidazo[4,5-f]quinoline (N-NO-IQ) to assess its possible role in the initiation of colon cancer by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). 14C-N-NO-IQ was incubated with different solvents and pHs in the presence and in the absence of nucleophiles and analyzed by HPLC. The products identified by electrospray ionization mass spectrometry include 2-chloro-3-methylimidazo[4,5-f]quinoline (2-Cl-IQ), 2,2'-azo-3,3'-dimethylimidazo[4,5-f]quinoline (AZO-IQ), 2-azido-IQ (2-N3-IQ), 3-methylimidazo[4,5-f]quinoline (deamino-IQ), and IQ. A variety of organic solvents were tested with 0.1 N HCl. 2-Cl-IQ and IQ were formed following acidification of all solvents. AZO-IQ was only formed in methanol. Deamino-IQ was the major product formed in all of the alcohols tested, except for methanol. Under acidic conditions that completely convert N-NO-IQ in 5 min (acetonitrile with 0.1 N HCl), 62% of N-NO-IQ remains after 30 min if dimethyl sulfoxide is substituted for acetonitrile. N-NO-IQ was stable in the physiologic pH range of 5.5-9.0 and did not react with nucleophiles over a 4 h period at pH 7.4 and 37 C. At acidic pH (pH 2.0) for 30 min and 37 C, N-NO-IQ becomes labile forming electrophile(s), which combine with biologically relevant nucleophiles. The reaction of N-NO-IQ at pH 2.0 followed first-order kinetics (t1/2 = 10 ¿ 2 min) and was significantly increased in 10 mM NaN3 (t1/2 = 2 ¿ 0.1 min). 2-N3-IQ was the major product observed in the latter incubation. N-NO-IQ binding to DNA at pH 2.0 is 100-fold more than that at pH 7.4. At pH 2.0, greater than 90% of the binding was inhibited by 10 mM NaN3. Thus, N-NO-IQ forms a reactive electrophile(s) at acidic pH, which binds DNA. N-NO-IQ reaction products may depend on the pH and the hydrophobic milieu of cells or tissues.