Perturbation of Surface Tension of Water by Polyhydric Additives: Effect on Glucose Oxidase Stability

An experimental investigation is reported on the influence of some polyhydric additives (ethanediol, 1,2-propanediol and glycerol) on the thermal behaviour of Aspergillus niger glucose oxidase. Spectroscopic measurements performed to follow protein unfolding showed that all the cosolvents destabilize the enzyme and caused an increase in the standard enthalpy and entropy of transition. Furthermore the melting temperature was found to be intimately related to the surface tension of the medium. The obtained results were interpreted as the consequence of preferential protein-cosolvent interactions determined by the perturbation of the surface tension of water.