Disodium SaltRibose, micromole/mg: 1.8 (theory 2.16); enzyme assay, micromole/mg: 1.5 (theory 2.2); P (org.) micromole/mg 5.2 (theory 6.36); ratio: p(org.)/ribose: 2.9 (theory 3.0)Note: This form of PRPP is slightly more stable than the tetrasodium salt often sold by other suppliers. Studies have shown the sodium salt to lose approx. 0.7 to 1.0% purity per week, even at -20<144>C. The dimagnesium salt may lose 0.3-0.6% purity per week under similar conditions.