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Radical formation of amino acid precursors in interstellar regions? Ser, Cys and Asp
Journal article   Peer reviewed

Radical formation of amino acid precursors in interstellar regions? Ser, Cys and Asp

D J Knowles, Tianfang Wang and J H Bowie
Organic & Biomolecular Chemistry, Vol.8(21), pp.4934-4939
2010
url
https://doi.org/10.1039/C0OB00232AView
Published Version

Abstract

It is proposed that the glycine precursor NH2CH2CN may be synthesised in interstellar dust clouds by the radical combination reactions NH2Ë™ + Ë™CH2CN → NH2CH2CN (ΔG = -302 kJ mol-1) and/or NH2CH2Ë™ + Ë™CN → NH2CH2CN (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 NH2CH2CN + HOË™ → NH2Ë™CHCN + H2O (ΔG = -130 kJ mol-1) is suggested to precede the radical coupling reactions NH2Ë™CHCN + RË™ → NH2CHRCN (RË™ = Ë™CH2OH, Ë™CH2SH and Ë™CH2CN) 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 Ë™CH2NH2, Ë™CH2OH, Ë™CH2SH and Ë™CH2CN are shown to be stable for the microsecond timeframe by a combination of theoretical calculations and the experimental mass spectrometric neutralization/reionization procedure.

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