title: Glycine formation pathway via hydantoin in the interstellar medium

authors: Kaori Kidachi, Masayuki Umemura, Mitsuo Shoji, Yu Komatsu, Megumi Kayanuma, Yasuteru Shigeta (University of Tsukuba)

abstract:  Amino acids in the primitive earth may have been originated in the interstellar medium (ISM).�@So far, various amino acid formation pathways in the ISM have been proposed by experimental and theoretical studies. We focus on hydantoin as a glycine precursor, which is detected in Murchison meteorite. The major glycine formation pathway via hydantoin was investigated by accurate quantum chemistry methods at the density functional theory (DFT) levels.
 The reaction barriers in gas-phase were so high that it is unlikely that glycine was formed during the lifetime of molecular clouds without external catalysis or outside energies such as UV irradiation and collisional heat. Organic molecules in the ISM are considered to be synthesized on icy interstellar dust grains. On the ice, water molecules play a catalytic role in proton-transfer and facilitate the basic transformations. Assuming reactions on the icy dust grains, we investigate the hydantoin and glycine formation pathway with a water molecule.