Revised conformational assignments and conformational evolution of tyrosine by laser desorption supersonic jet laser spectroscopy

The number of conformers and their structures of tyrosine are reassigned on the basis of resonance enhanced multiphoton ionization (REMPI), ultraviolet-ultraviolet hole burning (UV-UV HB), infrared (IR) dip spectra, and quantum chemical calculations. From comparison between REMPI and UV-UV HB spectra, it was found that 12 conformers coexist in the supersonic jet. The structures of these conformers are determined by the IR spectra and theoretical calculations. The number of conformers is more than that reported in the previous reports (8 conformers), and is rationalized by the systematic formation of conformers from simpler molecules without substituents, just like evolution. The importance of dipole-dipole interaction between an amino-acid chain and hydroxyl group at the benzene ring was also discussed.