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Issue 30, 2016
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Unified reaction pathways for the prebiotic formation of RNA and DNA nucleobases

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Abstract

The reaction pathways for the prebiotic formation of nucleobases are complex and lead to the formation of a mixture of products. In the past 50 years, there has been a concerted effort for identifying a unified mechanism for the abiotic origin of the biomolecules but with little success. In the present theoretical study, we identified two prominent precursors for the building up of RNA and DNA nucleobases under prebiotic conditions: (a) 1,2-diaminomaleonitrile (DAMN), which is a tetramer of hydrogen cyanide (HCN), and (b) formamide, a hydrolysis product of HCN; it is important to emphasize that HCN is the source of both precursors. We find that free radical pathways are potentially appropriate to account for the origin of nucleobases from HCN. The current study unites the formamide pathways with the DAMN pathways. The mechanisms for the formation of the RNA and DNA nucleobases (uracil, adenine, purine, cytosine) were studied by quantum chemical computations using density functional theory at the B3LYP/6-311G(d,p) level. All the routes involved proceed with relatively low energy barriers (within the error margin of DFT methods). We showed that the radical mechanisms for the formation of nucleobases could be unified through common precursors. The results demonstrated that 4-aminoimidazole-5-carbonitrile (AICN), which is a known precursor for nucleobases, is a product of DAMN. The overall mechanisms are internally consistent with the abiotic formation of the nucleobases, namely (a) under a meteoritic impact scenario on the early Earth's surface that generated high internal energy, and/or (b) in the (gas phase) interstellar regions without the presence of catalysts.

Graphical abstract: Unified reaction pathways for the prebiotic formation of RNA and DNA nucleobases

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Publication details

The article was received on 21 Apr 2016, accepted on 06 May 2016 and first published on 10 May 2016


Article type: Paper
DOI: 10.1039/C6CP02686A
Author version available: Download Author version (PDF)
Citation: Phys. Chem. Chem. Phys., 2016,18, 20177-20188
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    Unified reaction pathways for the prebiotic formation of RNA and DNA nucleobases

    Y. A. Jeilani, P. N. Williams, S. Walton and M. T. Nguyen, Phys. Chem. Chem. Phys., 2016, 18, 20177
    DOI: 10.1039/C6CP02686A

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