Role of ionic liquids in protein refolding: native/fibrillar versus treated lysozyme

Several ionic liquids (ILs) are known to revert aggregation processes and improve the in vitro refolding of denatured proteins. In this paper the capacity of a particular class of ammonium based ILs to act as refolding enhancers was tested using lysozyme as a model protein. Raman spectra of ILs treated fibrillar lysozyme as well as lysozyme in its native and fibrillar conformations were collected and carefully analyzed to characterize the refolding extent under the effect of the IL interaction. Results obtained confirm and largely extend the earlier knowledge on this class of protic ILs and indicate Ethyl Ammonium Nitrate (EAN) as the most promising additive for protein refolding. The experiment provides also the demonstration of the high potentiality of Raman spectroscopy as a comprehensive diagnostic tool in this field.