Quantification of ADP and ATP was performed using 31 P NMR by comparing the intensities of their respective peaks with that of the 31 P G6P resonance, the concentration of which was previously obtained by C NMR. (see Figure SI-9 in the Supplementary Information). The results are displayed in Table SI-4 of the Supplementary Information, together with the results of the quantification of G6P. Sephadex G-25 is a well established gel filtration medium for desalting. We observed by 31P NMR a total clearance of the phosphate buffer in the analysed fractions #44 to #47. However, due to the similar sizes of [U-13 C, U-2 H]-G6P , ADP and ATP ([U-13 C, U-2 H]-G6P : 279 Daltons , ADP: 427 Daltons, and ATP: 507 Daltons), these molecules were only partially separated. We found that fraction #45, although not the fraction containing the highest amount of G6P (see Figure SI-6 in the Supplementary Information), corresponded to the purest in terms of ATP and ADP contamination (90% purity).