PROTEIN HYDRATION IN SOLUTION - EXPERIMENTAL-OBSERVATION BY X-RAY ANDNEUTRON-SCATTERING

The structure of the protein-solvent interface is the subject of contr oversy in theoretical studies and requires direct experimental charact erization. Three proteins with known atomic resolution crystal structu re (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 o f E. coli ribonucleotide reductase) were investigated in parallel by x -ray and neutron scattering in H2O and D2O solutions. The analysis of the protein-solvent interface is based on the significantly different contrasts for the protein and for the hydration shell. The results poi nt to the existence of a first hydration shell with an average density approximate to 10% larger than that of the bulk solvent in the condit ions studied. Comparisons with the results of other studies suggest th at this may be a general property of aqueous interfaces.