Formamide-Based Prebiotic Synthesis of Nucleobases: A Kinetically Accessible Reaction Route

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Authors

ŠPONEROVÁ Judit MLÁDEK Arnošt ŠPONER Jiří FUENTES-CABRERA Miguel

Year of publication 2012
Type Article in Periodical
Magazine / Source The Journal of Physical Chemistry A
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://pubs.acs.org/doi/full/10.1021/jp209886b
Doi http://dx.doi.org/10.1021/jp209886b
Field Physical chemistry and theoretical chemistry
Keywords CHEMICAL EVOLUTION; HYDROGEN-CYANIDE; PRIMITIVE EARTH; RING FORMATION; ADENINE; ORIGIN; PURINE; MECHANISM; ENERGIES; WATER
Description Synthesis of nucleobases in nonaqueous environments is an alternative way for the emergence of terrestrial life, which could solve the fundamental problem connected to the hydrolytic instability of nucleic acid components in an aqueous environment. In this contribution, we present a plausible reaction route for the prebiotic synthesis of nucleobases in formamide, which does not require participation of the formamide trimer and aminoimidazole-carbonitrile intermediates. The computed activation energy of the proposed pathway is noticeably higher than that of the HCN-based synthetic route, but it is still feasible under the experimental conditions of the Saladino synthesis. We show that, albeit both the pyrimidine and purine ring formation utilizes the undissociated form of formamide, the dehydration product of formamide, HCN, may also play a key role in the mechanism. The rate determining step of the entire reaction path is the cyclization of the diaza-pentanimine precursor. The subsequent formation of the imidazole ring proceeds with a moderate activation energy. Our calculations thus demonstrate that the experimentally suggested reaction path without the involvement of aminoimidazole-carbonitrile intermediates is also a viable alternative for the nonaqueous synthesis of nucleobases.
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