Interaction of adenylic acid with alkaline earth metal ions in the crystalline solid and aqueous solution. Evidence for the sugar C'2-endo/anti, C'3-endo/anti and C'4-exon/anti conformational changes.
The reaction of adenosine 5'-monophosphoric acid (H2-AMP) with the alkaline earth metal ions has been investigated in aqueous solution at neutral pH. The solid salts of Mg-AMP.5H2O, Ca-AMP.6H2O, Sr-AMP.7H2O and Ba-AMP.7H2O were isolated and characterized by Fourier transform infrared, 1H-NMR spectroscopy and X-ray powder diffraction measurements. Spectroscopic and other evidence showed that the Sr-AMP.7H2O and Ba-AMP.7H2O are isomorphous, whereas the Mg-AMP.5H2O and Ca-AMP.6H2O are not similar. The Mg2+ binding is through the N-7 (inner-sphere) and the phosphate group (outer-sphere via H2O), while the Ca2+ binds to the phosphate group (inner-sphere) and to the base N-7 site (outer-sphere through H2O). The Sr2+ and Ba2+ bind to H2O molecules, H-bonding to the N-7, N-1 and the phosphate group (outer-sphere). In aqueous solution, an equilibrium between the inner- and outer-sphere metal ion bindings can be established. The sugar moiety exhibited C'2-endo/anti conformation, in the free H2-AMP acid and the magnesium salt, C'3-endo/anti in the calcium salt and unusual C'4-exo/anti, in the strontium and barium salts.
Tajmir-Riahi
H A
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Department of Chemistry, University of Laval, Quebec, Canada.
D000249:Adenosine Monophosphate; D001665:Binding Sites; D002236:Carbohydrate Conformation; D003855:Deoxyribose; D005583:Fourier Analysis; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008673:Metals, Alkaline Earth; D010710:Phosphates / Q000378:metabolism; D012266:Ribose; D012996:Solutions; D013055:Spectrophotometry, Infrared
D008673:Metals, Alkaline Earth; D010710:Phosphates; D012996:Solutions; D000249:Adenosine Monophosphate; D003855:Deoxyribose; D012266:Ribose