Protective action of trehalose and glucose on protein hydration shell clarified by using X-ray and neutron scattering

Abstract Sugars are well known to retain protein structures and to protect denaturation. Protective actions of sugars on protein structures have been discussed under issues of preferential hydration and/or interaction between sugar and protein. By using synchrotron radiation wide-angle X-ray scattering (SR-WAXS) and small-angle neutron scattering (SANS) methods, we have succeeded to obtain a direct evidence of the effect of trehalose and glucose on a protein structure and hydration. Myoglobin from horse-skeletal muscles was used as one of typical globular proteins. The sugars used were trehalose and glucose whose concentrations were varied from 0% w/w to 35% w/w. The experimental SR-WAXS and SANS data combined with theoretical scattering function simulation and fitting clearly show that both sugars are preferentially excluded from the hydration-shell region of the protein to preserve hydration-shell density. up to the sugar concentration of ∼25% w/w. Compared with that of glucose (monosaccharide), the preservation action of the protein hydration-shell is much evidently seen for the case of trehalose (disaccharide), which might relate to a role of the preferential production of trehalose by organisms against extreme environmental stress.