Changes in water structure induced by the guanidinium cation and implications for protein denaturation

PHYS 303

J. Nathan Scott, nscott@mail.med.upenn.edu, Nathaniel V Nucci, nvnucci@mail.med.upenn.edu, and Jane Vanderkooi. Department of Biochemistry and Biophysics, University of Pennsylvania, 257 Anatomy-Chemistry Bldg, 3620 Hamilton Walk, Philadelphia, PA 19104
The effect of guanidinium cation on H-bonding of water was analyzed using temperature-excursion Fourier transform infrared spectra of the OH stretching vibration in 5%H2O/95%D2O. A random network model of water's hydrogen bonding network served to analyze the absorption of an aqueous sample containing a range of different guanidine-HCl and guanidine-HBr concentrations in the temperature range of 5 to 90oC. The lower energy portion of the spectra arises from OH oscillators with strong, linear hydrogen bonds, while OH oscillators with weaker, bent hydrogen bonds contribute to the higher energy portion of the absorption band. This study provides strong evidence that guanidinium at high concentrations promotes linear hydrogen bonds, which we propose may play a significant role in protein denaturation.
 

PHYS Poster Session - Water Mediated Interactions
7:30 PM-10:00 PM, Wednesday, August 20, 2008 Pennsylvania Convention Center -- Hall C, Poster

Division of Physical Chemistry

The 236th ACS National Meeting, Philadelphia, PA, August 17-21, 2008