[Ion-exchange properties of DNA immobilized in acrylamide gel]

Ion-exchange of K+, Ca2+, Mg2+ and NH4+ on the Na+-DNA entrapped in acrylamide gel was studied. Under a definite percentage ratio between acrylamide and cross-linking agent (N,N'-methylenebisacrylamide) more than 95% of initial DNA was shown to be immobilized firmly and not to be washed out by salt solutions. Melting temperature and hypochromicity measurements of DNA extracted from the gel showed that denaturation of DNA has not taken place. The gel with immobilized DNA may be considered as ion-exchanger with phosphate fixed groups. It has been found that Mg2+, Ca2+, Na/, K+ and NH4+ are bounded with phosphate groups only, the degree of binding declines in the following order: Na+ less than or equal to K+ much less than Mg2+ less than Ca2+. The immobilization of DNA is suggested as a method of investigation of interaction between DNA and metal ions.