Abstract
The interaction of guanosine-5′-monophosphoric acid (H2-GMP) with the alkaline earth metal ions has been studied in aqueous solution at neutral pH. The crystalline salts of the type Mg-GMP·5H2O, Ca-GMP·6H2O, Sr-GMP·7H2O, and Ba-GMP·7H2O were isolated and characterized by Fourier transform ir, 1H-nmr and x-ray powder diffraction measurements. Two types of macrochelate complexes have been identified: (a) The direct metal–base and indirect metal–phosphate bindings (inner and outer sphere interaction) for the Mg(II), Ca(II), and Sr(II), ions; and (b) the indirect metal–base and direct metal–phosphate bindings (outer and inner sphere interaction) for the Ba(II) ion. In aqueous solution, an equilibrium exists between the base–metal–H2O…PO3 and base … H2O–M–PO3 interactions. The ribose moiety shows C3′-endo/anti conformation in the free acid; C2′-endo/anti in the Na2-GMP salt; C3′-endo/anti in the Mg(II)-, Ca(II)-, and Sr(II)-GMP salts; and C2′-endo/anti, in the Ba(II)-GMP salt.

This publication has 28 references indexed in Scilit: