Conformational and vibrational analyses of meta-tyrosine: An experimental and theoretical study

M-tyrosine is one kind of positional isomer of tyrosine which is widely applied in agrichemical, medicinal chemistry, and food science. However, the structural and vibrational features of m-tyrosine have not been reported or systematically investigated. In this work, potential energy surface (PES) calculations were used for searching and determining the stable zwitterionic conformers of m-tyrosine, and the Raman spectra of m-tyrosine and deuterated m-tyrosine were measured and interpreted based on theoretical computation. For the spectral simulation, several DFT-based quantum chemistry (QC) methods were employed, and the M06-2X functional with SMD solvent model was found to be best in reproducing the Raman spectra and geometrical property. As such, this study has not only presented a detailed study of m-tyrosine's vibrational property which is lack in the literature, but also may shed some light on the optimal choice of QC methods for calculation of conformations and vibrational properties of zwitterionic amino acids.