NMR studies on dynamic behavior of water molecule in aqueous denaturant solutions at 25 degrees C: Effects of guanidine hydrochloride, urea and alkylated ureas.

摘要

The spin-lattice relaxation times (T-1) of the 17(O) nucleus of a water molecule in guanidine hydrochloride, urea, and alkylated ureas at 25 degrees C were measured by NMR spectroscopy. Urea has no significant effect on the water structure. Also, guanidine hydrochloride as a stronger denaturant than urea does not perturb the water structure similar to urea. The change in the dynamic structure (B-R) of water was proportional to the carbon number of the alkyl chain of the alkylated urea. Compared to the results of alcohols and tetraalkylammonium solution, it is clear that the contribution of one carbon of the alkyl chain to the water structure is independent of the type of solute. The B-R of urea and its alkylated substances show a good correlation with the concentration of denaturation midpoints obtained on sperm whale myoglobin and cytochrome c. Because the water structure is not perturbed by urea and guanidine hydrochloride, these results indicate that the effect of hydrophobic hydration of denaturants becomes important for the denaturation of a protein with increasing hydrophobicity of the denaturants. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 33]