In situ measurements of the radiation stability of amino acids at 15–140 K

Abstract We present new kinetics data on the radiolytic destruction of amino acids measured in situ with infrared spectroscopy. Samples were irradiated at 15, 100, and 140 K with 0.8-MeV protons, and amino-acid decay was followed at each temperature with and without H 2 O present. Observed radiation products included CO 2 and amines, consistent with amino-acid decarboxylation. The half-lives of glycine, alanine, and phenylalanine were estimated for various extraterrestrial environments. Infrared spectral changes demonstrated the conversion from the non-zwitterion structure NH 2 CH 2 (R) COOH at 15 K to the zwitterion structure + NH 3 CH 2 (R) COO − at 140 K for each amino acid studied.