Time-Dependent Density Functional Theory Study Of The X-Ray Emission Spectroscopy Of Amino Acids And Proteins

The non-resonant X-ray emission spectroscopy of amino acids and a dipeptide have been studied using timedependent density functional theory (TDDFT) calculations at the nitrogen and oxygen K-edges. Comparison with higher level calculations and experimental data shows that TDDFT with the CAM-B3LYP exchange-correlation functional and (Z+1)6-311G* basis set provides an accurate description of the spectra. Calculations for model alpha-helix and beta-sheet structures show the spectra to relatively insensitive to the structure of peptide bond, with the greatest variation observed at the oxygen K-edge.