Department of Biochemistry, Bose Institute, P-1/12, CIT Scheme VIIM, Calcutta, 700054, India.
J Biomol Struct Dyn. 2012;30(4):394-406. doi: 10.1080/07391102.2012.682206. Epub 2012 Jun 11.
The effect of exposing 2'-deoxyadenosine (dA), 5'-dAMP, 3'-dAMP, dApA, dA(pdA)(19,) and poly(dA): oligo(dT) to iron/H(2)O(2) in the presence and absence of ethanol or NADH has been studied. HPLC retention times, enzyme treatments, radio-labeled substrates, UV absorption spectra, and fast atom bombardment mass spectrometry (FABMS) have been used to distinguish 20 products arising from the reaction, of which 16 have been identified and four anomers proposed by comparison with earlier gamma radiation studies. The radical responsible for the reactions seems to be analogous to radiation-derived [Formula: see text], has many products in common, but has some novel ones probably specific for Fenton-induced damage. Two new dimeric adducts arising from the generation of hydroxylamine at N7 and its subsequent condensation with two known sugar damage products, dR-adenine-N1-oxide, and two isomers of dR-FAPy arising from radical attacks at C4 and C5, may be considered novel in the present study. Unlike radiation-derived [Formula: see text], the radical under study is difficult to eliminate due to its generation in the proximity of the substrate molecules. It is proposed that the iron binds to the phosphate group and generates the radical in its vicinity. Strand breaks in dA(pdA)(11) resulting from the Fenton reaction are of two types, spontaneous and alkali-labile. Duplex DNA is less sensitive to attack by this radical, as its various degradation products are a subset of those obtained with monomer substrates and only dR-FAPy production is relatively enhanced for poly (dA): oligo (dT) as compared to those from other substrates.
研究了在有或没有乙醇或 NADH 的情况下，将 2'-脱氧腺苷（dA）、5'-dAMP、3'-dAMP、dApA、dA(pdA)(19,) 和聚(dA)：寡(dT)暴露于铁/H(2)O(2)中的影响。使用 HPLC 保留时间、酶处理、放射性标记的底物、紫外吸收光谱和快原子轰击质谱 (FABMS) 来区分反应产生的 20 种产物，其中 16 种已被鉴定，通过与早期γ辐射研究比较，提出了四种差向异构体。负责反应的自由基似乎类似于辐射衍生的[公式：见文本]，有许多共同的产物，但也有一些新的产物可能是芬顿诱导损伤所特有的。两种新的二聚加合物，一种是由于 N7 生成羟胺及其随后与两种已知的糖损伤产物 dR-腺嘌呤-N1-氧化物缩合而产生的，另一种是由于自由基在 C4 和 C5 处攻击产生的两种 dR-FAPy 异构体，在本研究中可能被认为是新的。与辐射衍生的[公式：见文本]不同，由于其在底物分子附近生成，因此难以消除研究中的自由基。据推测，铁与磷酸盐结合并在其附近生成自由基。Fenton 反应导致 dA(pdA)(11)中的链断裂有两种类型，即自发断裂和碱不稳定断裂。双链 DNA 对这种自由基的攻击不那么敏感，因为其各种降解产物是单体底物获得的产物的子集，并且只有 dR-FAPy 的产生相对于其他底物而言，对聚(dA)：寡(dT)的相对增强。
