IR-CRLAS OF SMALL BIOMOLECULES

$^{a}$J.J. Scherer, D. Voelkel, D.J. Rakestraw, J.B. Paul, C.P. Collier, R.J. Saykally, and A. O'Keefe, Chem. Phys. Lett. 245, 273 (1995). $^{b}$J.B. Paul, C.P. Collier, R.J. Saykally, J.J. Scherer, and A. O'Keefe, J. Chem. Phys. A 101, 5211 (1997).Author Institution: Department of Chemistry, UC BerkeleyInfrared cavity ringdown laser absorption spectroscopy (IR-CRLAS) is a novel technique which has been used to study a wide variety of $systems.^{a,b}$ Currently, we report the application of this method to study hydration of small biomolecules. We have recorded mid-infrared absorption spectra for several jet-cooled amino acids, including valine and arginine. We have also collected spectra of (water),, biomolecule clusters for these systems. In addition, we have recorded spectra in the Amide I region $(1600-1700 cm^{-1})$ for jet-cooled GlyGly, which has allowed us to begin examination of peptide backbone conformation issues. Along with ab initio frequency calculations, these results provide insight in answering questions such as the gas-phase conformation distribution and the zwitterionic state of these systems

Psychophysics of sweet and fat perception in obesity: problems, solutions and new perspectives

Psychophysical comparisons seem to show that obese individuals experience normal sweet and fat sensations, they like sweetness the same or less, but like fat more than the non-obese do. These psychophysical comparisons have been made using scales (visual analogue or category) that assume intensity labels (e.g. extremely) which denote the same absolute perceived intensity to all. In reality, the perceived intensities denoted by labels vary because they depend on experiences with the substances to be judged. This variation makes comparisons invalid. Valid comparisons can be made by asking the subjects to rate their sensory/hedonic experiences in contexts that are not related to the specific experiences of interest. Using this methodology, we present the evidence that the sensory and hedonic properties of sweet and fat vary with body mass index. The obese live in different orosensory and orohedonic worlds than do the non-obese; the obese experience reduced sweetness, which probably intensifies fat sensations, and the obese like both sweet and fat more than the non-obese do. Genetic variation as well as taste pathology contribute to these results. These psychophysical advances will impact experimental as well as clinical studies of obesity and other eating disorders