Influence of glycerol on the structure and thermal stability of lysozyme: a dynamic light scattering and circular dichroism study.

Photon correlation spectroscopy and circular dichroism have been used to study the role of hydration in the structure and thermostability of the model protein lysozyme in water-glycerol mixtures. Two cases have been considered: water-rich and glycerol-rich regimes of concentrations. We follow the thermal denaturation both by optical spectral changes and hydrodynamic radius variations. This methodology allows us to emphasize the relevant role played by hydrophobic interactions during the process in aqueous solutions and, in glycerol, to distinguish the non-cooperative melting of secondary structure, supporting the view of a protein transition to a molten globule-like state.

Cauchy relation in relaxing liquids.

The Cauchy-like relation M(infinity) = A + BG(infinity) has recently been found to hold for the high frequency limit values of the longitudinal modulus M(infinity) and transverse modulus G(infinity) of viscoelastic liquids, with B approximately 3 in all the investigated systems. The Brillouin scattering results here reported for curing epoxy systems and thermal glass formers give evidence for the validity of a Cauchy-like relation M(') = A + BG(') for the real part of the elastic moduli measured at finite frequencies. Our results suggest as well the validity of a pure Cauchy relation DeltaM = 3 DeltaG for the relaxation strengths of longitudinal and shear moduli in relaxing liquids.