  The structural properties resulting from the reciprocal influence between
water and three well-known homologous disaccharides, namely trehalose, maltose
and sucrose, in aqueous solutions have been investigated in the 4-66 wt %
concentration range by means of molecular dynamics computer simulations.
Hydration numbers clearly show that trehalose binds to a larger number of water
molecules than do maltose or sucrose, thus affecting the water structure to a
deeper extent. Two-dimensional radial distribution functions of trehalose
definitely reveal that water is preferentially localized at the hydration sites
found in the dihydrate crystal, this tendency being enhanced when increasing
trehalose concentration. In a rather wide concentration range (4-49 wt %), the
fluctuations of the radius of gyration and of the glycosidic dihedral angles of
trehalose indicate a higher flexibility with respect to maltose and sucrose. At
sugar concentrations between 33 wt % and 66 wt %, the mean sugar cluster size
and the number of sugar-sugar hydrogen bonds (HBs) formed within sugar clusters
reveal that trehalose is able to form larger clusters than sucrose but smaller
than maltose. These features suggest that trehalose-water mixtures would be
more homogeneous than the two others, thus reducing both desiccation stresses
and ice formation.
