Irreversible oxidative damage at both aromatic side chains and dipeptide linkage occurs in the aromatic N- and C-protected dipeptides 7â11 upon exposure to the environmental pollutants NO2Ë and O3. The reaction proceeds through initial oxidation of the aromatic ring by in situ generated NO3Ë, or by NO2Ë, respectively, which leads to formation of nitroaromatic products. The indole ring in Phe-Trp undergoes oxidative cyclization to a pyrroloindoline. An important reaction pathway for dipeptides with less oxidisable aromatic side chains proceeds through fragmentation of the peptide bond with concomitant acyl migration. This process is likely initiated by an ionic reaction of the amide nitrogen with the NO2Ë dimer, N2O4.
在接触环境污染物
NO2·和O3时,芳香性N端和C端保护的二肽7–11发生不可逆的氧化损伤,涉及芳香侧链和二肽链节。反应首先通过原位生成的
NO3·或 ·对芳香环的氧化进行,进而导致硝基
芳烃产物的形成。Phe-Trp中的
吲哚环经历氧化环化,形成
吡咯啉。对于芳香侧链氧化性较弱的二肽,其重要的反应途径是通过肽键的断裂伴随酰基迁移。这个过程可能是由酰胺氮与 ·二聚体
N2O4的离子反应引发的。