Water-rich solutions of carbohydrates, peptides and proteins have been studied by means of extended frequency range depolarized light scattering (EDLS), in the range 0.3 GHz - 40 THz. This allowed us to separate solute from solvent dynamics and bulk from hydration water. Internal motions, rotational diffusion and, eventually, the boson peak of the solute are analyzed and compared to previous inelastic neutron scattering results. The retardation factor of hydration water with respect to the bulk is found to be in the range 3-4 in a simple monosaccharide and up to 7-8 in proteins, corresponding to a perturbed fraction of water that extends from the first layer up to 2-3 layers over the solute molecule. This implies the existence of collective effects, possibly related to the complex patchwork of hydrophilic and hydrophobic sites that interact with hydration water.
Multi-scale dynamics in water solutions of carbohydrates, peptides and proteins revealed by extended frequency range depolarized light scattering
FIORETTO, Daniele
2012
Abstract
Water-rich solutions of carbohydrates, peptides and proteins have been studied by means of extended frequency range depolarized light scattering (EDLS), in the range 0.3 GHz - 40 THz. This allowed us to separate solute from solvent dynamics and bulk from hydration water. Internal motions, rotational diffusion and, eventually, the boson peak of the solute are analyzed and compared to previous inelastic neutron scattering results. The retardation factor of hydration water with respect to the bulk is found to be in the range 3-4 in a simple monosaccharide and up to 7-8 in proteins, corresponding to a perturbed fraction of water that extends from the first layer up to 2-3 layers over the solute molecule. This implies the existence of collective effects, possibly related to the complex patchwork of hydrophilic and hydrophobic sites that interact with hydration water.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
