Amino acids chemical stability submitted to solid state irradiation: the case study of leucine, isoleucine and valine

A solid state radiolysis was conducted to examine the reactivity of amino acids towards high energy dose of gamma radiations. The presence of amino acids in the bulk of meteorites has raised the question of "if" and eventually "how" they could have been important in the development of life on Earth. The presence of radioactive elements in Solar System bodies could have played a crucial role in amino acids survival and in the formation of different organic molecules. The radioactive elements produced a total radiation dose of 14 MGy during the life of Solar System (4.6 x 10(9) years). The aim of this study is to investigate the amino acids capacity to survive at a dose of gamma-irradiation equivalent to 1.05 x 10(9) years of Solar System life. In particular, we examined the behavior of three essential amino acids (leucine, isoleucine and valine) submitted to a total dose of 3.2 MGy. We choose to irradiate L-enantiomers to analyze the behavior of a single enantiomer to radiations. We identified the radiation products formed in solid state radiolysis by mass spectrometric analysis and we were able to enlighten some common reactions. These reactions are particularly important to rationalize the formation of prebiotic molecules. Moreover, we studied the radioracemization process, the formation of D-enantiomer promoted by gamma-irradiation.