Mechanism for the abiotic synthesis of uracil via UV-induced oxidation of pyrimidine in pure H{sub 2}O ices under astrophysical conditions

Journal Article · Tue Sep 14 04:00:00 EDT 2010 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3478524· OSTI ID:21559913

Bera, Partha P; Nuevo, Michel; Sandford, Scott A; Lee, Timothy J ^[1]; Milam, Stefanie N ^[1]

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1. Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, California 94035 (United States)

The UV photoirradiation of pyrimidine in pure H{sub 2}O ices has been explored using second-order Moeller-Plesset perturbation theory and density functional theory methods, and compared with experimental results. Mechanisms studied include those starting with neutral pyrimidine or cationic pyrimidine radicals, and reacting with OH radical. The ab initio calculations reveal that the formation of some key species, including the nucleobase uracil, is energetically favored over others. The presence of one or several water molecules is necessary in order to abstract a proton which leads to the final products. Formation of many of the photoproducts in UV-irradiated H{sub 2}O:pyrimidine=20:1 ice mixtures was established in a previous experimental study. Among all the products, uracil is predicted by quantum chemical calculations to be the most favored, and has been identified in experimental samples by two independent chromatography techniques. The results of the present study strongly support the scenario in which prebiotic molecules, such as the nucleobase uracil, can be formed under abiotic processes in astrophysically relevant environments, namely in condensed phase on the surface of icy, cold grains before being delivered to the telluric planets, like Earth.

• OSTI ID: 21559913
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 10 Vol. 133; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
60 APPLIED LIFE SCIENCES
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ASTROPHYSICS
AZINES
BARYONS
CALCULATION METHODS
CHEMICAL REACTIONS
CHEMISTRY
CHROMATOGRAPHY
DENSITY FUNCTIONAL METHOD
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
HYDROXYL RADICALS
ICE
MOLECULES
NUCLEONS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
OXYGEN COMPOUNDS
PERTURBATION THEORY
PHOTOCHEMISTRY
PHYSICS
PROTONS
PYRIMIDINES
RADICALS
SEPARATION PROCESSES
SURFACES
SYNTHESIS
URACILS
VARIATIONAL METHODS
WATER