Benchmarking density functionals and Gaussian basis sets for calculation of core-electron binding energies in amino acids

A variety of density functionals and Gaussian basis sets has been studied for performance in calculations of core-electron binding energies of the carbon, nitrogen, and oxygen nuclei in the gaseous amino acids glycine, alanine, proline, threonine, and methionine. The main goal of this study is the identification of methods that will be sufficiently accurate and efficient to be used for analysis of experimental X-ray photoelectron spectra of amino acids, large polypeptides, and DNA nucleosides in various environments. The various methods studied are evaluated based on consideration of their performance for calculation of relative conformer energies, core-electron binding energies, and chemical shifts of the binding energies, using common popular density functionals with small basis sets.