Valine Radiolysis by H+, He+, N+, and S15+ MeV Ions

Cíntia A. P. da Costa (1) , Gabriel S. Vignoli Muniz (2) , Philippe Boduch (3) , Hermann Rothard (3) , Enio F. da Silveira (1)

1 PUC-Rio - Pontifícia Universidade Católica do Rio de Janeiro [Brasil] = Pontifical Catholic University of Rio de Janeiro [Brazil] = Université catholique pontificale de Rio de Janeiro [Brésil]
2 Universidade Federal de São Paulo
3 CIMAP - UMR 6252 - Centre de recherche sur les Ions, les MAtériaux et la Photonique

Radiolysis of biomolecules by fast ions has interest in medical applications and astrobiology. The radiolysis of solid D-valine (0.2-2 µm thick) was performed at room temperature by 1.5 MeV H + , He + , N + , and 230 MeV S 15+ ion beams. The samples were prepared by spraying/dropping valine-water-ethanol solution on ZnSe substrate. Radiolysis was monitored by infrared spectroscopy (FTIR) through the evolution of the intensity of the valine infrared 2900, 1329, 1271, 948, and 716 cm −1 bands as a function of projectile fluence. At the end of sample irradiation, residues (tholins) presenting a brownish color are observed. The dependence of the apparent (sputtering + radiolysis) destruction cross section, σ d , on the beam stopping power in valine is found to follow the power law σ d = aS e n , with n close to 1. Thus, σ d is approximately proportional to the absorbed dose. Destruction rates due to the main galactic cosmic ray species are calculated, yielding a million year half-life for solid valine in space. Data obtained in this work aim a better understanding on the radioresistance of complex organic molecules and formation of radioproducts.

Mots clés: amino acid; valine; MeV ion irradiation; radiolysis; infrared absorption spectroscopy; destruction cross section; stopping power dependence

Domaines: Radiochimie

Cíntia A. P. da Costa, Gabriel S. Vignoli Muniz, Philippe Boduch, Hermann Rothard, Enio F. da Silveira. Valine Radiolysis by H+, He+, N+, and S15+ MeV Ions. International Journal of Molecular Sciences, 2020, 21 (5), pp.1893. ⟨10.3390/ijms21051893⟩. ⟨hal-03032962⟩