Determination of Radiation Dose Leading to Molecular Chain Destruction of Amino Acids

The soft X-ray absorption spectroscopy (XAS) spectra of Alanine, L-and D-phenylalanine, and L-and D-tyrosine dissolved in a solid state were measured at BL17SU of SPring-8. The spectra exhibited characteristic features dependent on the molecular structure. It was found that almost the same spectra were obtained for Alanine and Phenylalanine, while for Tyrosine, the spectral shape indicated a drastic change owing to the existence of the oxygen 1s? p* transitions of COO- over bar . It is found that the X-ray irradiation promotes the destruction reaction of amino acids and changes the spectral shape during the spectroscopic measurement. The molecular destruction rate by X-ray was estimated from the change of spectral intensity as a function of irradiation time. Our results indicate that the ratio of the destruction rate depends on the molecular structure and is facilitated by the oxygen 1s ? p* transitions.