Figure 1.

Defining the conditions to allow the quantification of purine nucleotides from extracts of cardiac muscle. (A) Schematic of ATP with Mg²⁺ ion. The proton used for distinct quantification is highlighted in red. (B) The effect of Mg²⁺ ion concentration in equimolar concentrations of ATP and ADP. The presence of Mg²⁺ alters the chemical shift of the ATP proton, but not the ADP; resulting in a convergence of these peaks with physiological concentrations of Mg²⁺. (C) ¹H-NMR spectra from polar metabolites extracted from perfused mouse hearts without (red) and with EDTA (blue). In the presence of EDTA, the ATP and ADP peaks are clearly distinct and easily quantifiable. (D) The effect of extract pH on the separation of the purine proton peaks, note the high mobility of the AMP proton. (E) The pH sensitivity creatine (Cr) and phosphocreatine (PCr) protons.