Intermolecular Interactions between Aromatic Amino Acids Investigated by Ultraviolet Photodissociation Spectroscopy of Hydrogen-Bonded Clusters of Histidine and Tryptophan Enantiomers.

Intermolecular interactions between aromatic amino acids were investigated by ultraviolet photodissociation spectroscopy of hydrogen-bonded protonated clusters of histidine (His) and tryptophan (Trp) enantiomers in the gas phase. Product ion spectra and photodissociation spectra in the wavelength range of the S-S transition of Trp at several temperatures (8-100 K) were obtained using a tandem mass spectrometer equipped with an electrospray ionization source and a cold ion trap. l-Trp detachment forming protonated His was the main pathway.