Sugar bioprotective effects on thermal denaturation of lysozyme: Insights from Raman scattering experiments and molecular dynamics simulation

The bioprotective properties of trehalose, sucrose and maltose on lysozyme protein are studied using Raman spectroscopy and molecular dynamics simulation. The temperature dependencies of the α-helical unfolding processes are determined in presence of different sugars and at various concentrations using the amide I band. The energies of stabilization and acting forces are discussed. The problem of the threshold sugar concentration needed to protect proteins is addressed. The results point out that the three sugars exhibit very similar bioprotective behaviors in the investigated temperature and concentration ranges and suggest that the difference between their respective effects arise mostly from the different denaturated states of lysozyme in the three sugar solutions. Indeed, trehalose gives rise to a significantly more important shift of the denaturation temperature T_m and of the Gibbs net free energy Δ(ΔG_ND) of stabilization of lysozyme with respect to the two other sugars.