Innershell Absorption Spectroscopy of Amino Acids at All Relevant Absorption Edges

The C, N, and O K-edge near-edge X-ray absorption fine structure spectra of the 22 most common proteinogenic α-amino acids in the zwitterionic form collected from solvent-free polycrystalline powder films in the partial electron yield mode are reported. Spectral features common to all amino acids, as well as distinctive fingerprints of specific subgroups of these compounds, are presented and discussed.