Fujita S
Int J Radiat Biol Relat Stud Phys Chem Med. 1984 Apr;45(4):371-7. doi: 10.1080/09553008414550511.
On the radiolysis of uridine and some other nucleosides in aqueous solution, a pH-dependent liberation of uracil or the corresponding base was found. e-aq and HO-.2 gave no freed bases, although many oxidizing radicals, including OH, Cl-.2, Br-.2, (CNS)-.2 and SO-.4, did cause the release of unaltered bases, depending on the pH of the solutions. The base yields were generally high at pH greater than or equal to 11, with the exception of SO-.4, which gave a rather high yield of uracil (from uridine) even in the pH region of less than or equal to 11. The pattern of the base formation against pH varied with the reacting radical, but was the same for the different nucleosides. With regard to the OH radical system, bases are considered to be formed after H-abstraction of the sugar moiety at low pH. The other oxidizing radicals, however, may cause base release by attack at the base. It is possible that O-, present at high pH as the dissociated form of OH, may act partly as an oxidizing radical. A plausible mechanism of 31'-radical formation is discussed.
在水溶液中对尿苷及其他一些核苷进行辐射分解时，发现尿嘧啶或相应碱基的释放与pH有关。水合电子（e-aq）和羟自由基（HO-.2）不会使碱基释放，不过包括羟基自由基（OH）、二氯自由基（Cl-.2）、二溴自由基（Br-.2）、二硫氰酸根自由基（(CNS)-.2）和硫酸根自由基（SO-.4）在内的许多氧化自由基，会根据溶液的pH值导致未改变的碱基释放。除了硫酸根自由基外，碱基产率在pH大于或等于11时通常较高，硫酸根自由基即使在pH小于或等于11的区域也能从尿苷中产生相当高的尿嘧啶产率。碱基形成与pH的关系模式随反应自由基的不同而变化，但不同核苷的情况相同。对于羟基自由基体系，在低pH值下，碱基被认为是在糖部分的氢被夺取后形成的。然而，其他氧化自由基可能通过攻击碱基导致碱基释放。在高pH值下以OH的离解形式存在的O-可能部分起到氧化自由基的作用。本文讨论了3'-自由基形成的一种合理机制。
