Fluorescence study of laccase from Trametes versicolor under the effects of pH, chemical denaturants and ionic liquids

Herein, we have studied the fluorescence emissions for the laccase from Trametes versicolor in aqueous solutions for various pH, chemical denaturants and ionic liquids (ILs). The fluorescence spectra were recorded from 310 to 450 nm after exciting the Tryptophan (Trp) at 280 nm. We have shown that the fluorescence intensity reaches its maximum around pH = 4 whereas the excitation for pH < 4 and pH > 7 causes a red shift. The influence of the superficial charges distribution on the fluorescence emission was also investigated. The effects of Pyrrolidinuim Formate ([pyrr][F]) and Morphilinium Formate ([morph][F]) ILs on the laccase fluorescence emissions for various volumetric fractions was studied. From the variation of the maximum wavelength, lambda(max), versus the volumetric fractions, we have determined the midpoint concentration C-1/2 which are equals to 42.62% and 40.91% for [pyrr][F] and [morph][F], respectively. For urea and GdmCl chemical denaturants, we have shown that the fluorescence intensity decreases with increasing denaturants concentration. We have also used the linear regression model to determine the energy of unfolding, Delta G(D). The midpoint concentrations for urea and GdmCl denaturants which are around 3.06 and 3.17 M respectively are determined. (C) 2016 Elsevier B.V. All rights reserved.