Subtle Interactions of Cupric Ion with Nucleic Acid and Components* by Earl Frieden and Jeanne Alles

In a study of the mechanism of activation of the copper enzyme, ascorbic acid oxidase, it was observed that most compounds which activate this enzyme have the common property of forming complex compounds with cupric ion (l-3). Among these activating substances were ribonucleic acid,’ deoxyribonucleic acid, and certain of their constituents. These substances showed a surprisingly strong affinity for cupric ion which has not been emphasized by earlier reports on such interactions (4-6). We have therefore examined the interaction of cupric ion and nucleic acid and certain of its components in order to compare the intensity of these interactions with other chelators of biological origin. The availability of many purified fragments of RNA and DNA permitted an analysis of the structural specificity of these reactions. The strength of the interaction of cupric ion with RNA, DNA, and their constituents may indicate an important role of these compounds in the biochemistry of trace elements such as copper. Similarly, these interactions may be of significance in assessing the biological role of RNA and DNA.