Protein hydration in solution: Experimental observation by x-ray and neutron scattering

TLDR

The protein–solvent interface structure remains controversial and needs direct experimental characterization. The authors examined three crystal‑resolved proteins (lysozyme, E. coli thioredoxin reductase, and protein R1) using x‑ray and neutron scattering in H₂O and D₂O, exploiting the distinct contrasts of protein and hydration shell to analyze the interface.

Abstract

The structure of the protein–solvent interface is the subject of controversy in theoretical studies and requires direct experimental characterization. Three proteins with known atomic resolution crystal structure (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 of E. coli ribonucleotide reductase) were investigated in parallel by x-ray and neutron scattering in H 2 O and D 2 O 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 point to the existence of a first hydration shell with an average density ≈10% larger than that of the bulk solvent in the conditions studied. Comparisons with the results of other studies suggest that this may be a general property of aqueous interfaces.