Jump to main content
Jump to site search

Issue 37, 2015
Previous Article Next Article

Acetylene as an essential building block for prebiotic formation of pyrimidine bases on Titan

Author affiliations

Abstract

Prebiotic building blocks for the formation of biomolecules are important in understanding the abiotic origin of biomolecules. However, there is a limited choice of the building blocks as precursors for the biomolecules. Acetylene (HCCH) is found in Titan's atmosphere and is an abiotic-precursor of pyrimidine bases. HCCH reacts with urea to form both cytosine and uracil. The mechanisms for the formation of both cytosine and uracil were studied by density functional theory at B3LYP/6-311G(d,p) level. Ethynyl radicals (˙CCH) are relevant for the chemistry of Titan's atmosphere therefore both HCCH and ˙CCH were evaluated as carbon sources. The pathways, for both HCCH and ˙CCH, lead to intermediates with an unsaturated-group that facilitate the formation of the six-membered ring of the pyrimidine bases. The predicted structures for cytosine and uracil were compared with labeled cytosine and uracil that were formed from the reaction of DCCD with urea. The results suggest that cytosine is formed from HCCH while uracil is formed from ˙CCH. The mechanisms are energetically feasible and there is no conclusive evidence for the preferred pathway (HCCH or ˙CCH). The pathways were further extended for the formation of both uric acid and 8-oxoguanine from HCCH and urea, and demonstrate the utility of HCCH as a carbon source for diverse biomolecules. Biuret is identified as a precursor for the pyridimine bases, and it unifies the free radical pathways for the pyrimidine bases with those of triazines. The pathways are appropriate for the reducing atmosphere that creates both radicals and electrons due to ionizing radiation on Titan. The mechanisms are feasible for the extraterrestrial formation of the pyrimidine bases.

Graphical abstract: Acetylene as an essential building block for prebiotic formation of pyrimidine bases on Titan

Back to tab navigation

Supplementary files

Publication details

The article was received on 04 Jun 2015, accepted on 21 Aug 2015 and first published on 24 Aug 2015


Article type: Paper
DOI: 10.1039/C5CP03247D
Author version available: Download Author version (PDF)
Citation: Phys. Chem. Chem. Phys., 2015,17, 24294-24303
  •   Request permissions

    Acetylene as an essential building block for prebiotic formation of pyrimidine bases on Titan

    Y. A. Jeilani, C. Fearce and M. T. Nguyen, Phys. Chem. Chem. Phys., 2015, 17, 24294
    DOI: 10.1039/C5CP03247D

Search articles by author

Spotlight

Advertisements