Electron spin resonance and electron nuclear double resonance study of X-irradiated deoxyadenosine: proton transfer behavior of primary ionic radicals.
Electron spin resonance and electron nuclear double resonance study of X-irradiated deoxyadenosine: proton transfer behavior of primary ionic radicals.
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DOI：
10.2307/3579684
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发表时间：
1998
影响因子：
3.4
通讯作者：
W. Nelson;E. Sagstuen;E. Hole;D. Close
中科院分区：
文献类型：
--
作者：
W. Nelson;E. Sagstuen;E. Hole;D. Close
在10 K下辐照后的脱氧腺苷晶体（无水形式）的研究发现了四个以碱为中心的自由基和一个以糖为中心的自由基。自由基R1，热稳定到约100 K和光漂白容易与白色光，是产品的脱质子化的氨基由初级自由基阳离子。自由基R2，也热稳定到约100 K，是在N3的初级自由基阴离子的质子化的产物。自由基R3在170 K左右稳定，位于脱氧核糖部分的中心，显然是从C4 '上净夺取氢的结果。自由基R4和R5是C2和C8 H-加成产物，具有这些物质的典型偶联。R4和R5均在10 K下形成，并且在室温下稳定。R1在几个系统中的行为提供了额外的证据，证明氢键环境显着参与控制直接由电离产生的自由基的稳定（或形成），如前所述（Radiat. Res. 131，272-284，1992）。从比较的氨基基团的氢键环境中，自由基的结构的R1被稳定，我们得出结论，氧原子作为质子受体是重要的，在允许自由基稳定所需的电荷和自旋分离。特别是，ROH结构的氧似乎最有效的通过容易地允许多质子洗牌通过一个机制相当于质子交换。集体的结果表明，这些产品的稳定是不可能的，除非电荷和自旋可以分开的至少一个干预分子。
A study of deoxyadenosine crystals (anhydrous form) after irradiation at 10 K found four base-centered radicals and one sugar-centered radical. Radical R1, thermally stable to about 100 K and photobleachable easily with white light, was the product of deprotonation at the amino group by the primary radical cation. Radical R2, also thermally stable to about 100 K, was the product of protonation at N3 of the primary radical anion. Radical R3, stable to about 170 K, was centered in the deoxyribose moiety and evidently was the result of net hydrogen abstraction from C4'. Radicals R4 and R5 were the C2 and C8 H-addition products with couplings typical of those species. Both R4 and R5 were formed at 10 K and were stable at room temperature. The behavior of R1 in several systems provides additional evidence for significant involvement of the hydrogen-bonding environment in controlling the stabilization (or formation) of radicals resulting directly from ionization, as described previously (Radiat. Res. 131, 272-284, 1992). From comparison of amino-group hydrogen-bonding environments in which radicals with the structure of R1 were stabilized, we conclude that oxygen atoms as proton acceptors are important in permitting the charge and spin separation necessary for radical stabilization. In particular, oxygens of ROH structures seem most efficient by readily permitting a multi-proton shuffle through a mechanism amounting to proton exchange. The collective results show that stabilization of these products is unlikely unless the charge and spin can be separated by at least one intervening molecule.