EXOCYCLIC DNA ADDUCTS--SYNTHETIC AND ANALYTIC STUDIES

描述：（申请人描述）本部分描述的有机化学、合成化学和分析化学旨在支持相关项目中的生物和物理化学研究。主要目标是为合成DNA低聚物提供以其dmt -磷酰胺形式衍生的修饰的2'-脱氧核苷（必要时n保护）。修饰的核苷包括三组：(a)代表或模拟由亲电试剂或活性氧化物质引起的DNA损伤的核苷，(b)用于DNA修复酶研究的正常天然底物的不可水解模拟物，以及激活后形成外环加合物或链间交联的核苷。两大主题主导着合成化学。第一种方法是在核苷侧链上有一个邻乙二醇，通过高碘酸氧化可以转化为醛。后者将在合成后产生所需的内收碱基。用这种方法可以原位合成与芳烃醛、巴豆醛、脂质过氧化加合物、天然碱基和核糖内酯有关的加合物。这种方法也会产生交叉链接。第二个主题涉及使用“碳”嘌呤和嘧啶作为正常碱基和氧化或内合形式的内源性DNA损伤的稳定或不可水解的模拟物。这些将用于：(a)涉及DNA修复酶（如MutY）运作机制的研究，包括外翻（翻转）过程，(b)用于诱变机制的研究，以及(c)获得DNA修复酶复合物的晶体结构。

DESCRIPTION: (Applicant's Description) The organic, synthetic, and analytical chemistry described in this section of the program is designed to support biological and physico-chemical studies in the accompanying projects. The primary goal is to provide modified 2'-deoxynucleosides derivatized in the form of their DMT-phosphoramidites (N-protected where necessary) for synthetic DNA oligomers. The modified nucleosides comprise three groups: (a) those that represent or mimic damage induced in DNA by electrophiles or by reactive oxidizing species, (b) those that are non-hydrolysable mimics of the normal natural substrates for studies of DNA repair enzymes, and those that after activation will form exocyclic adducts or inter-strand crosslinks. Two main themes dominate the synthetic chemistry. The first involves having a vicinal glycol in a nucleoside side-chain that by periodate oxidation can be converted to an aldehyde. The latter will generate the desired adducted base, post-synthetically. Adducts related to araldehyde, crotonaldehyde, lipid peroxidation adducts, the natural abasic site, and ribonolactone will be synthesized in situ by this method. Cross-links also will be generated by this approach. The second theme concerns the use of "carba" purines and pyrimidines as stable or non-hydrolysable mimics of both normal bases and oxidized or adducted forms of endogenous DNA damage. These will be used: (a) in studies involving mechanisms by which DNA repair enzymes such as MutY operate, including the eversion (flip-out) process, (b) for studies of mutagenic mechanisms, and (c) to obtain crystal structures of complexes with DNA repair enzymes.