H NMR Study of Protonation and Mg(II) Coordination of AMP, ADP, and ATP at 25, 50, and 70 °C

Abstract

The interactions of adenosine 5‘-monophosphate (AMP), adenosine 5‘-diphosphate (ADP), and adenosine 5‘-triphosphate (ATP) with protons and with Mg2+ in aqueous solutions have been studied by 1H NMR spectroscopy at 25, 50, and 70 °C. Upfield shifts of H-8 were found in the pH ranges where protonation of phosphate groups occurs for the three nucleotides at all temperatures studied, indicating that AMP, ADP, and ATP adopt an anti conformation at these temperatures. The order of the H-8 upfield shift is AMP > ADP ∼ ATP. The shift decreases slightly at 50 and 70 °C. Chemical shift measurements for the three nucleotides in the presence of Mg2+ give no indication of the existence of an interaction between Mg2+ and the adenine ring in the Mg2+−nucleotide complexes under the experimental conditions of this study. The mechanism of the deshielding effect of phosphate groups on H-8, and the effects of temperature and pH on the intramolecular interaction of these nucleotides are discussed.

Quantum chemical analysis of ATP, GTP and related compounds in gas phase

“…H NMR experiments [24,25] show that the molecule exists in water in an anti-configuration, and the triphosphate tail is fully deporotonated under neutral conditions especially when complexed with Mg 2+ . Mg 2+ has a strong catalytic activity related to its ability to elongate one of the anhydride P-O bonds, with an estimated reaction barrier of 13.5 kcal mol -1 for a pyrophosphate dianion [26][27][28].…”

ATP Hydrolysis in Water − A Density Functional Study

“…In the case of ATP, the total energy differs from that of the linear phosphate tail configuration (one H-bond less) by 8.3 kcal/mol. The ATP and GTP molecules in Figure 1 are shown in their anti conformation, which according to the NMR experiments, 18 is the dominant conformation of deprotonated ATP in water. The syn conformation is probably more stable in the gas phase, since it allows hydrogen bonding between the H-2 in the adenine ring and one O R atom.…”

“…[14][15][16][17][18] H-NMR experiments 16,17 show that the molecule exists in water in a linear anti configuration, and the triphosphate tail is fully deprotonated under neutral conditions (Scheme 1), especially when complexed with Mg 2+ . Calorimetric measurements of Mg(ATP) 2-complexes 18 show that the enthalpy change is slightly positive on chelate formation between Mg 2+ and phosphate oxygens, so that it is an entropy-driven process. Entropy is also responsible for the fact that Mg 2+ binds to ATP more readily than to adenosine 5′-diphosphate (ADP).…”

Coordination mode of adenosine 5′-diphosphate in ternary systems containing Cu(II), Cd(II) or Hg(II) ions and polyamines

“…In the pH range of (ADP)H 3 (tn) and (ADP)H 3 (Put) occurrence ( Fig. 1(a) and (b)), the phosphate group of the nucleotide is partly deprotonated, whereas in the conditions of formation of (ADP)H 2 (tn) and (ADP)H 2 (Put) the nucleotide is totally deprotonated [40,41]. An increase in the equilibrium constants for deprotonated species, relative to the values for triprotonated species, is a result of deprotonation of the phosphate group.…”