Interaction of guanylic acid with the Mg(II), Ca(II), Sr(II), and Ba(II) ions in the crystalline solid and aqueous solution: evidence for the ribose C2'-endo/anti and C3'-endo/anti conformational changes.
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 metalbase 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.
Tajmir-Riahi
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Photobiophysics Research Center, University of Quebec, Trois-Rivieres, Canada.
D001464:Barium / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D003460:Crystallization; D006157:Guanosine Monophosphate / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000737:chemistry; D008673:Metals, Alkaline Earth / Q000737:chemistry*; D008968:Molecular Conformation; D010710:Phosphates / Q000737:chemistry; D012266:Ribose / Q000737:chemistry; D012996:Solutions; D013324:Strontium / Q000737:chemistry; D014961:X-Ray Diffraction
D008673:Metals, Alkaline Earth; D010710:Phosphates; D012996:Solutions; D001464:Barium; D012266:Ribose; D006157:Guanosine Monophosphate; D008274:Magnesium; D002118:Calcium; D013324:Strontium