Oscillographic polarography of deoxyribonucleic acid degradation products

Abstract

Alternating-current oscillographic polarography was used for the analysis of highly polymerised DNA. In an ammonium formate medium DNA produces an indentation which arises at the same potential as that at which the indentation produced by free deoxyguanylic acid arises. Other characteristics of the indentations produced by these two acids also agree well, and for this reason the oscillopolarographic activities of a number of the degradation products of DNA have been studied. In an ammonium formate medium deoxyribo-apyrimidinic acid yielded the same anodic indentation as that yielded by DNA, whereas neither apurinic acid, nor degradation products of DNA from which all bases except adenine had been removed, nor polydeoxyribose phosphate, produced this indentation. The results obtained prove that the anodic indentation yielded by DNA is produced by the deoxyguanylic acid bound in the DNA molecule. Free deoxycytidylic acid yields, in an ammonium formate medium, a cathodic indentation and this type of indentation is not produced by intact DNA. The cathodic indentation was formed only after the purines had been removed from the DNA molecule, while it disappeared after deamination of the apurinic acid. It is assumed that a part of the pyrimidine ring of deoxycytidylic acid bound in the molecule of DNA is sterically blocked, with the result that a reaction on the electrode is prevented, whereas the corresponding part of the purine ring of deoxyguanilic acid is not sterically blocked.