The crit. micelle concentration (cmc) of Triton X-100 and the no. of exposed thiols of creatine kinase have been measured with urea and guanidine hydrochloride (GHCl) as sep. additives. The changes of hydrophobic energy of hydrocarbon chains caused by urea and GHCl in the micellization process have been calculated, and the parameter that shows the capabilities for urea and GHCl to reduce hydrophobic energy has been obtained. The capacity for GHCl to cut down the hydrophobic energy is 3.5-fold that for urea. The capacity for GHCl to lead to the exposure of buried thiols is 3.2-fold that for urea, which implies that the reduction of hydrophobic energy caused by urea and GHCl is the major factor of denaturation of creatine kinase within the range of additive concns. studied.

Key words: INFLUENCING FACTORS, SODIUM CHLORIDE, CHAIN STRUCTURE, HYDROPHOBILITY, CRITICAL DENSITY, CREATINE KINASE, UREA, GUANIDINE HYDROCHLORIDE