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 400eV, (4.6±0.5)×10 −2 for 407eV and (3.2±1.5)×10 −2 for 860eV 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 402eV peak, which is a fingerprint of the peptide bond. The important role of surface to chemical evolution is discussed.
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