Protection against Dehydration: A Neutron Diffraction Study on Aqueous Solutions of a Model Peptide and Trehalose

The ability of a wide class of organisms to reversibly go through cycles of suspended life and active metabolism, depending on the turnover of drought and normal water availability conditions, represents a challenging issue. The interest in the natural mechanism for drought survival has grown over time along with the request for always more efficient conservation techniques for biological materials. Carbohydrates, such as trehalose, accumulated in the cytoplasm of drought resistant cells, are considered responsible for desiccation tolerance. Nonetheless, a detailed description of the interaction between trehalose and biomolecules is not yet established. Neutron diffraction experiments show that trehalose entraps a layer of water molecules in the first shell of a model peptide, N-methylacetamide, without direct bonding with it. This evidence contrasts the hypothesis that trehalose substitutes water and supports the opposite view, namely, of trehalose forming a protective shell which entraps a layer of water molecules at the surface of proteins, thus avoiding structural damage due to drought conditions.