Different molecular conformations, i.e., native, urea-unfolded, guanidine hydrochloride(GuHCl)-unfolded, urea-reduced-unfolded, GuHCl-reduced-unfolded, of lysozyme was systematically studied by reversed-phase liquid chromatography(RPLC), and weak-cation exchange chromatography(WCX), and the stoichiometric parameters Z in stoichiometeric displacement model(SDM). The difference of molecular conformations of lysozyme with their disulfide bonds cleaved or could not be found in RPLC and WCX in terms of retention. However, they could not be used to distinguish their reduced states from non-reduced ones. Each difference of molecular conformations of lysozyme, caused by urea and GuHCl solution, can only be characterized with Z. The definition of the degree of the unfolded was introduced to characterize the change of conformation.
