Coupling of complex aromatic ring vibrations to solvent through hydrogen bonds: Effect of varied on-ring and off-ring hydrogen-bonding substitutions

PHYS 311

Nathaniel V Nucci,, J. Nathan Scott,, and Jane Vanderkooi. Department of Biochemistry and Biophysics, University of Pennsylvania, 422 Curie Blvd., Philadelphia, PA 19104
In this study, we examine the coupling of a complex ring vibration to solvent through hydrogen bonding interactions. We compare a group of physiologically important small molecules which vary by single differences in hydrogen-bonding substitution, including phenylalanine, tyrosine, and the tyrosine-derivative neurohormones. By examining the temperature dependence of infrared absorptions of these molecules, we show that complex, many-atom vibrations can be coupled to solvent through hydrogen bonds and that the extent of that coupling is dependent on the degree of both on- and off-ring hydrogen-bonding substitution. Attribution of the spectral shifts to vibrational coupling through hydrogen bonds is performed using analysis of the solvent dependence of optical properties of the molecules and ab initio calculations. Our findings indicate that a full understanding of biomolecule vibrational properties must include consideration of explicit hydrogen-bonding interactions with the surrounding microenvironment.

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