Resonance Raman studies of hydrogen-bonded solutions: quantitative comparisons of experiment with ab initio calculations

Resonance Raman studies of simple peptides have provided a new view of the electronic excitations of these important chromophores. The large effect of isotropic substitution and of hydrogen bonding on resonance Raman spectra provide a new method for testing theoretical calculations. These calculations can be refined by direct comparison of theory with experiment and also used to evaluate the likelihood that further experiments will provide interesting new information. Our recent work has shown how fruitful this cyclic interaction can be. In this on going exploration we are developing experimental methods and testing theoretical descriptions of the electronic excitations of peptides and related ultraviolet chromophores of proteins in solution. The specific areas of interest are (1) examination of the effect of hydrogen bonding on the electronic excitation of peptides; (2) evaluation of the effects of fluctuations in solvation on the electronic excitations of peptides; and (3) studies of the nπ* and higher energy electronic excitations of peptides predicted by theory and potentially important in the description of circular dichroism.