Studies of protein hydration in aqueous solution by high‐resolution nuclear magnetic resonance spectroscopy

Abstract

AbstractIndividual hydration water molecules in aqueous protein solutions have been observed using experimental schemes for homonuclear two‐dimensional and heteronuclear three‐dimensional NMR experiments in H2O solution, which do not require suppression of the solvent line by presaturation. In these experiments, the location of the hydration waters is determined from their nuclear Overhauser effects (NOEs) with individual hydrogen atoms of distinct amino acid residues. In the basic pancreatic trypsin inhibitor (BPTI), four internal water molecules that had been reported in three different crystal forms were also found to be in the same locations in the solution structure, with lifetimes with respect to exchange of the water protons in excess of 0.3 ns. Additional NOEs with polypeptide protons located on the protein surface may involve either hydration water molecules or hydroxyl protons of amino acid side chains. Their total number is small compared to the number of NOEs expected from the hydration water molecules identified in the crystal structures of BPTI.