摘要：

During the reaction of H 2O 2 with deoxyribonucleotides or their components, the ultraviolet absorption decreased at rates which were for cytosine > thymine > adenine > guanine. The chromatographic separation of the reaction mixtures revealed that all four bases were partially removed from both deoxynucleotides and deoxynucleosides, the reaction rates being for thymine > adenine > cytosine > guanine. Since no deoxynucleosides were formed from deoxynucleotides, H 2O 2 apparently cleaved only the N- glycosidic linkage, the phosphate group not being involved. dpA, dA, and adenine gave rise to an additional ultraviolet-absorbing base, A 1. Kinetic arguments showed that dpA was first altered to dpA 1 and then A 1 was liberated. A quantitative analysis of the ultraviolet-absorbing products showed that the base liberation was only partially responsible for the loss of ultraviolet absorption: some of the purine and the majority of the pyrimidine bases must have been converted to non-ultraviolet-absorbing products, the relative effectiveness of alteration being for cytosine > thymine > adenine > guanine. Experiments with nucleotides labeled in the base moiety showed that most of the bases which lost their ultraviolet absorption remained attached to the deoxyribose phosphate. The relative frequency with which the doexynucleotide molecules were decomposed was for adenine > thymine > cytosine > guanine. 0.1 M NH 2OH also liberated and destroyed bases, similar to H 2O 2, but it produced a different altered adenine: A 2.

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