Computaional studies of saccharide hydration: Spectroscopy, structure and dynamics

Molecular Dynamicssimulations using 'on the fly' density functional theory potentialspotentials with the CP2K package, are used to explore the hydration of cellobiose-(H2O)n, n= 1, 2, 5. Vibrational spectra is computed from the trajectory, in theclassical approximation, and found to compare well with experimental spectra ofthe OH groups (for n = 1,2), at T ~ 40 and 300 K. The simulations show hopping of water between sites of the sugar, and evaporation as temperature is increased. Conformational changes of the sugar are also studied. The simulations throw light on the dynamics of water molecules at different temperatures and on the spectroscopicmanifestations of dynamics. Simulations of cellobiose and other sugars complexed with large number of water molecules (up to 40), were carried out using empirical force fields and semi-empirical electronic structure potentials. It is found in all cases, that the sugars show surfactant properties, e.g. have a preference for positions at the surface of the water cluster