title: The use of ascorbate as an oxidation inhibitor in prebiotic amino acid synthesis: a cautionary note.
abstract: It is generally thought that the terrestrial atmosphere at the time of the origin of life was CO(2)-rich and that organic compounds such as amino acids would not have been efficiently formed abiotically under such conditions. It has been pointed out, however, that the previously reported low yields of amino acids may have been partially due to oxidation by nitrite/nitrate during acid hydrolysis. Specifically, the yield of amino acids was found to have increased significantly (by a factor of several hundred) after acid hydrolysis with ascorbic acid as an oxidation inhibitor. However, it has not been shown that CO(2) was the carbon source for the formation of the amino acids detected after acid hydrolysis with ascorbic acid. We therefore reinvestigated the prebiotic synthesis of amino acids in a CO(2)-rich atmosphere using an isotope labeling experiment. Herein, we report that ascorbic acid does not behave as an appropriate oxidation inhibitor, because it contributes amino acid contaminants as a consequence of its reactions with the nitrogen containing species and formic acid produced during the spark discharge experiment. Thus, amino acids are not efficiently formed from a CO(2)-rich atmosphere under the conditions studied.
authors.affiliation: Department of Chemistry and Biotechnology, Yokohama National University, Yokohama, 240-8501, Japan. kuwahara@astrobio.k.u-tokyo.ac.jp
authors.forename: Hideharu
authors.initials: H
authors.lastname: Kuwahara
authors.forename: Midori
authors.initials: M
authors.lastname: Eto
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Kawamoto
authors.forename: Hironari
authors.initials: H
authors.lastname: Kurihara
authors.forename: Takeo
authors.initials: T
authors.lastname: Kaneko
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Obayashi
authors.forename: Kensei
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D000596:Amino Acids / Q000138:chemical synthesis*; D001205:Ascorbic Acid / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006868:Hydrolysis; D009584:Nitrogen / Q000737:chemistry*; D000069497:Origin of Life; D010084:Oxidation-Reduction
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D002245:Carbon Dioxide; D009584:Nitrogen; D001205:Ascorbic Acid