Models for enzyme-copper-nucleic acid interaction. 1H NMR line broadening study of the interaction of some copper complexes with cytidine.

Sodium (salicylideneglycylglycinato) copper(II), bis(2,9-dimethyl-1, 10-phenanthroline)copper (II), and (1,5-bis (benzimidazol-2-yl)-3-thiapentane) copper(II) were interacted with cytidine in D2O. For all the complexes, the broadening of the 1H signals of cytidine is found to be in the order H(5) greater than H(6) greater than H(1'); this suggests the binding of N (3) and O2 sites of cytidine to copper. The possibility that the ribose moiety is also involved in coordination cannot be ruled out. The complete broadening of the H(5) signals for the last complex above is because of the coordinative unsaturation of the complex. It has been concluded that steric factors and coordinative unsaturation in the complexes affect the extent of interaction with cytidine.