Interaction of deoxyguanylic acid with alkaline earth metal ions. Evidence for the deoxyribose C3'-endo/anti, O4'-endo/anti and C2'-endo/anti conformational transitions.

The interaction of 2'-deoxyguanosine-5'-monophosphoric acid (H2-dGMP) with the alkaline earth metal ions has been investigated in aqueous solution at neutral pH. The solid salts of the type Mg-dGMP.5H2O Ca-dGMP.6H2O, Sr-dGMP.7H2O and Ba-dGMP.7H2O were isolated and characterized by FT-IR, proton-NMR and X-ray powder diffraction measurements. Two types of metal-nucleotide interactions have been identified: (a) the indirect metal-base and the direct metal-phosphate bindings (outer- and inner-sphere interaction), for the Mg(II) and Sr(II) ions and (b) the direct metal-base and direct metal-phosphate bindings (inner-sphere interaction), for the Ca(II) and Ba(II) ions. In aqueous solution, a dynamic equilibrium of the type base-metal-H2O. . .PO3 in equilibrium base. . .H2O-metal-PO3 is present. The deoxyribose moiety exhibits C3'-endo/anti conformation, in the Mg(II)-, Ca(II)-, Sr(II)- and Ba(II)-dGMP salts.