Table 2 Reqirements of NMR structural biology
TargetSmall molecule ligand
Quantity: 2–20 mgQuantity: 0.5–2 mg
Solubility: >0.1 mMSolubility: 0.1–2 mM (in aqueous buffer), preferably higher for weaker ligands
Stability: days to weeksStability: days
Isotope labeling: 13C, 15N, (2H)Isotope labeling: not needed, but should contain hydrogens
Size: <25 kDa (protonated) < 70 kDa (deuterated)Affinity: Covalent or tight (no limits) to weak (several mM), but must not be in the intermediate exchange regime in the chemical shift time scale