Conformational features of disulfide intact and reduced forms of hen egg white lysozyme in aqueous solution in the presence of trifluoroethanol (TFE): Implications for protein folding intermediates

The conformational features of reduced and disulfide intact hen egg white l ysozyme in aqueous 2,2,2-trifluoroethanol (TFE) solutions have been examine d using circular dichroism and fluorescence spectroscopies. We find that no n-native like and molten globule like states are induced in reduced lysozym e, with non-native like and native like alpha helicities and with reduced a ccessibility of tryptophans to collisional quencher acrylamide, in the pres ence of TFE as judged from circular dichroism and fluorescence experiments. We correlate our results to kinetic hydrogen-deuterium exchange NMR result s of the refolding of lysozyme available in the literature. We discuss the implications of our results for disulfide bond formation and protein foldin g intermediates.