Abstract
Among the naturally occurring gluco-disaccharides, trehalose has the highest glass transition temperature (Tg) and the largest activation energy of enthalpy relaxation in the glassy state. These properties are very favorable as a desiccation protectant. Here, to understand at molecular level why trehalose has such unique properties, we carried out molecular dynamics simulations for the glassy states of trehalose and neotrehalose. By comparing these results, we revealed the following points: 1) there is no significant difference in the average number of intermolecular hydrogen bonds between the glassy state of trehalose and that of neotrehalose, 2) the translational motion and the void volume in the glassy matrix both are smaller in trehalose than in neotrehalose, and 3) the glycosidic bond of trehalose takes a single conformation but that of neotrehalose has more than two. These results suggested that the higher Tg and higher stability of trehalose glass is due to the increasing packing density of the glassy matrix, which originates from the conformational simplicity of this sugar, a characteristic feature of α, α-1,1-linkage.
