EDTA influence on the DNA complexation with Cu2+

Abstract

Interaction of copper ions with DNA in solution in the presence of EDTA is studied with the method of circular dichroism. The results show that the complex of DNA nucleobases with copper ions is destroyed at the EDTA addition to the solution. Investigation of the solutions of thymidine (Thy), CuCl2 and EDTA by the method of electrospray ionization mass spectrometry reveals the existence of compound complexes [Y4−] · Cu2+ · Na+ · 2H+ · Thy, 2{[Y4−] · Cu2+ · Na+ · 2H+ · Thy} and 2{[Y4−] · Cu2+ · 3Na+ · Thy}, where [Y4−] is completely deprotonated form of EDTA. In all complexes observed the Thy : [Y4−] : Cu2+ binding stoichiometry is 1 : 1 : 1. One can expect the appearance of nucleobases complexes with Cu2+ and EDTA in DNA sites with destabilised secondary structure as a result of heat motion of intact DNA, or in ligand binding locus, and also in the sites with primary structure defects. In the DNA solutions with Cu2+ or with Cu2+ and EDTA the increase in DNA secondary structure disturbance under the action of UVC light is observed. Refs 44. Figs 5. Tables 1.