Co-ordination behaviour of nucleic acid bases against the Fe(I)(N0)2 group in solution. I. Purines: ESR study

The binding sites of purine bases in the presence of the Fe(I)(NO)2 group were investigated on the basis of the nuclear hyperfine structure of the electron spin resonance spectra. Selective isotopic substitution with 15NO was used to clarify coordination. Coupling constants and different types of complexes were determined by means of computer-simulated ESR spectra. Comparison was made with the binding sites of nucleotides and it was concluded that N-7, in the unidazole ring, is the preferred binding site, A structure with two base molecules bonded to the iron atom was proposed. Finally ε{lunate} azaguanine, an antitumoral agent, was studied and the special behaviour of this antimetabolite was demonstrated in the biologically-interesting pH values. © 1975.