Chemical evolution of amino acid induced by soft X-ray with synchrotron radiation

Soft X-ray induced chemical evolution from glycine (Gly) to glycyl-glycine (glycine dimer or Gly-Gly) was studied for sublimated films of Gly. Values of quantum yield of Gly dimer formation were determined by high performance liquid chromatography (HPLC) technique to be: (1.2 ± 0.2) × 10−1 for 400 eV, (4.6 ± 0.5) × 10−2 for 407 eV and (3.2 ± 1.5) × 10−2 for 860 eV irradiation, respectively. We measured X-ray absorption spectra of irradiated Gly films at near edge region of nitrogen K-edge, as a function of X-ray dose. Formation of Gly-Gly was confirmed by the appearance and growth of 402 eV peak, which is a fingerprint of the peptide bond. The important role of surface to chemical evolution is discussed.