Difference between guanidinium chloride and urea as denaturants of globular proteins: The possibility of application to improved refolding processes

Abstract

The difference in the effect of guanidinium chloride (GdnHCl) and urea on the unfolding of hen egg-white lysozyme was evaluated mostly by means of circular dichroism(CD) measurements at pH 6.2 and at room temperature. The CD spectrum of lysozyme in 6M GdnHCl revealed the unfolded state, but that in 8M urea was almost identical with that of the native lysozyme. The effectiveness of urea as a denaturant corresponding to GdnHCl was attained by increasing the ionic strength of the solution by introducing lithium chloride(LiCl). This suggests that GdnHCl affects hydrophobic and ionic interactions simultaneously, while urea affects almost solely the hydrophobic interaction. Knowledge that the bifunctional ability of GdnHCl can be divided into two independent reagent abilities will provide a new tool to assist with correct refolding of unfolded proteins. © 1992, The Pharmaceutical Society of Japan. All rights reserved.