A structuring and eventual exclusion of water surrounding backbone hydrogen bonds takes place during protein fold-ing as hydrophobic residues cluster around such bonds. Taken as an average over all hydrogen bonds, the extent of desolvation is nearly a constant of motion, as revealed by re-examination of the longest all-atom trajectory with explicit solvent [ & (1998)Science 282, 740].Furthermore, this extent of desolvation is pre-served across native soluble proteins, except for cellular prion proteins
