title: Radical formation of amino acid precursors in interstellar regions? Ser, Cys and Asp.
abstract: It is proposed that the glycine precursor NH(2)CH(2)CN may be synthesised in interstellar dust clouds by the radical combination reactions NH(2)˙ + ˙CH(2)CN → NH(2)CH(2)CN (ΔG = -302 kJ mol(-1)) and/or NH(2)CH(2)˙ + ˙CN → NH(2)CH(2)CN (ΔG = -414 kJ mol(-1)). All calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31+G(d) level of theory. This paper extends that concept to radical/radical coupling reactions to form Ser, Cys and Asp precursor nitriles. The hydrogen abstraction process NH(2)CH(2)CN + HO˙→ NH(2)˙CHCN + H(2)O (ΔG = -130 kJ mol(-1)) is suggested to precede the radical coupling reactions NH(2)˙CHCN + R˙→ NH(2)CHRCN (R˙ = ˙CH(2)OH, ˙CH(2)SH and ˙CH(2)CN) to form nitrile precursors of the amino acids Ser, Cys and Asp. These three reactions are all favourable (ΔG = -240, -227 and -223 kJ mol(-1)). The radical species ˙CH(2)NH(2), ˙CH(2)OH, ˙CH(2)SH and ˙CH(2)CN are shown to be stable for the microsecond timeframe by a combination of theoretical calculations and the experimental mass spectrometric neutralization/reionization procedure.
authors.affiliation: Department of Chemistry, The University of Adelaide, South Australia, 5005, Australia.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Knowles
authors.forename: Tianfang
authors.initials: T
authors.lastname: Wang
authors.forename: John H
authors.initials: JH
authors.lastname: Bowie
mesh_terms: D001224:Aspartic Acid / Q000138:chemical synthesis* / Q000737:chemistry; D003545:Cysteine / Q000138:chemical synthesis* / Q000737:chemistry; D009570:Nitriles / Q000138:chemical synthesis* / Q000737:chemistry; D012694:Serine / Q000138:chemical synthesis* / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D009570:Nitriles; D001224:Aspartic Acid; D012694:Serine; D003545:Cysteine