Radiolysis of amino acids by heavy and energetic cosmic ray analogues in simulated space environments: α-glycine zwitterion form

Abstract

In this work, we studied the stability of the glycine molecule in the\ncrystalline zwitterion form, known as {\\alpha}-glycine\n($^{+}$NH$_{3}$CH$_{2}$COO$^{-}$) under action of heavy cosmic ray analogs. The\nexperiments were conducted in a high vacuum chamber at heavy ions accelerator\nGANIL, in Caen, France. The samples were bombarded at two temperatures (14 K\nand 300 K) by $^{58}$Ni$^{11+}$ ions of 46 MeV until the final fluence of\n$10^{13}$ ions cm$^{-2}$. The chemical evolution of the sample was evaluated\nin-situ using Fourrier Transformed Infrared (FTIR) spectrometer. The\nbombardment at 14 K produced several daughter species such as OCN$^-$, CO,\nCO$_2$, and CN$^-$. The results also suggest the appearing of peptide bonds\nduring irradiation but this must be confirmed by further experiments. The\nhalflives of glycine in Interstellar Medium were estimated to be 7.8 $\\times\n10^3$ years (300 K) and 2.8 $\\times 10^3$ years (14 K). In the Solar System the\nvalues were 8.4 $\\times 10^2$ years (300 K) and 3.6 $\\times 10^3$ years (14 K).\nIt is believed that glycine could be present in space environments that\nsuffered aqueous changes such as the interior of comets, meteorites and\nplanetesimals. This molecule is present in proteins of all alive beings. So,\nstudying its stability in these environments provides further understanding\nabout the role of this specie in the prebiotic chemistry on Earth.\n