Conformational features of reduced and disulfide intact forms of hen egg white lysozyme in aqueous solution in presence of 3-chloro-1, 2-propanediol and dioxane: Implications for protein folding intermediates

Conformational features of reduced and disulfide intact hen egg white lysoz yme in aqueous 1,4-dioxane and 3-chloro-1, 2-propanediol solutions have bee n examined using circular dichroism and fluorescence spectroscopy. We find that in presence of 1, 4-dioxane, reduced lysozyme assumes a relatively com pact conformational form with secondary structure closer to native state an d no tertiary structure as judged by peptide and aromatic CD spectra and AN S binding studies monitored by fluorescence. Further, in presence of 40% (v /v) 3-chloro-1, 2-propanediol, disulfide intact lysozyme (DI-lysozyme) assu mes a conformational form with native like secondary structure and no terti ary structure akin to a molten globule state. We correlate our results to k inetic hydrogen- deuterium exchange NMR results of the refolding of lysozym e available in literature and suggest that the conformational forms observe d in our study could be models for kinetic intermediates in the refolding o f lysozyme.