title: Stable isotope analysis at the molecular level:  a new approach for determining the origins of amino acids in the Murchison meteorite.
abstract: A combined gas chromatography/isotope ratio mass spectrometry (GC/IRMS) method has been developed that permits the direct stable carbon isotope analysis of N(O)-trifluoroacetyl-isopropyl esters of individual amino acids and their respective enantiomers at nanomole abundances.  Calculation of the original delta 13C values of the amino acids is accomplished via a correction for the carbon introduced during the derivatization process.  Previous GC/IRMS analyses of individual amino acids in the non-hydrolyzed water extract of an interior sample of a Murchison meteorite stone revealed an enrichment in 13C relative to terrestrial organic matter, in agreement with previous findings for bulk extracts.  The range of amino acid delta 13C values (+5 to +30%, PDB) suggests possible kinetic effects during synthesis.  In this study, an apparent kinetic isotope effect was also observed for the amino acid products of a spark discharge experiment.  These preliminary results are supportive of a similar mechanism for the abiotic synthesis of amino acids in the Murchison meteorite.
authors.affiliation: School of Geology and Geophysics, The University of Oklahoma, Norman 73019, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Engel
authors.forename: S A
authors.initials: SA
authors.lastname: Macko
authors.forename: Y
authors.initials: Y
authors.lastname: Qian
authors.forename: J A
authors.initials: JA
authors.lastname: Silfer
mesh_terms: D000409:Alanine / Q000032:analysis / Q000138:chemical synthesis; D000596:Amino Acids / Q000032:analysis / Q000138:chemical synthesis*; D000621:Aminoisobutyric Acids / Q000032:analysis / Q000138:chemical synthesis; D001224:Aspartic Acid / Q000032:analysis / Q000138:chemical synthesis; D002247:Carbon Isotopes; D002849:Chromatography, Gas / Q000379:methods; D019418:Evolution, Chemical; D018559:Exobiology; D005998:Glycine / Q000032:analysis / Q000138:chemical synthesis; D013058:Mass Spectrometry / Q000379:methods; D019110:Meteoroids; D014633:Valine / Q000032:analysis / Q000138:chemical synthesis; D015091:beta-Alanine / Q000032:analysis / Q000138:chemical synthesis
chemical_list: D000596:Amino Acids; D000621:Aminoisobutyric Acids; D002247:Carbon Isotopes; D015091:beta-Alanine; D001224:Aspartic Acid; C032737:isovaline; D014633:Valine; D000409:Alanine; D005998:Glycine