Effect of 1-alkanols on the native conformation of lysozyme

The technique of intensity photon correlation spectroscopy was utilised to investigate the native conformation of lysozyme in water-ethanol and water- tert-butanol mixtures as a function of alcohol concentration in the water-r ich region of composition (cosolvent mole fraction x(2)< 0.08). A non-trivi al behaviour of the hydrodynamic radius was obtained, characterised by a mi nimum at x(2)=0.02 in water-ethanol and x(2)=0.005 in water-tert-butanol mi xtures. This behaviour is similar to that of the partial molar volume of 1- alkanols in water and reflects changes in alcohol-water structure. The resu lts are discussed in connection with the effect of the alcohol in modulatin g solvent-mediated interactions.