Hydration and aggregation of a simple amino acid: The case of glycine

Abstract Glycine is the smallest and simplest amino acid with several applications in the chemical and pharmaceutical industries. To date, a wide conflicting literature about the hydration and aggregation of glycine is available. The aim of the present work is to study the hydration and the aggregation properties of glycine in aqueous solution as a function of glycine concentration and temperature. These features are determined at atomistic level, by neutron diffraction with isotopic H/D substitution, augmented by a Monte Carlo simulation. Concerning the glycine-glycine aggregation, the coexistence of direct and water-mediated interactions is demonstrated. In particular, chains or cyclic dimers are preferred, depending on concentration and temperature. Finally, the perturbation of the water network, induced by glycine, is reported and described in detail. Present results give relevant information about formation of polymers and crystallization seeds in glycine solutions.