Radical pathways for the formation of non-canonical nucleobases in prebiotic environments

Kaur, Sarabjeet; Sharma, Purshotam

doi:10.1039/c9ra08001e

Cited by 7 publications

(6 citation statements)

References 45 publications

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“…The only constraint of this plausible prebiotic scenario is the relative constancy of the pH throughout the hydrothermal system because cyanide can only undergo polymerization at pH = 8–10 and can only be concentrated by evaporation at alkaline pH, and most of the N-heterocycles included in this study are sensitive to acidic hydrolysis conditions. In this way, the present work complements previous studies of the possible prebiotic synthesis of triazines from urea 10 , 35 and from cyanamide 64 , showing alternative abiotic pathways for their production.…”

Section: Discussionsupporting

confidence: 74%

Prebiotic synthesis of noncanonical nucleobases under plausible alkaline hydrothermal conditions

Pérez-Fernández

Vega

Rayo-Pizarroso

et al. 2022

Sci Rep

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Herein, the potential of alkaline hydrothermal environments for the synthesis of possible ancestral pre-RNA nucleobases using cyanide as a primary source of carbon and nitrogen is described. Water cyanide polymerizations were assisted by microwave radiation to obtain high temperature and a relatively high pressure (MWR, 180 °C, 15 bar) and were also carried out using a conventional thermal system (CTS, 80 °C, 1 bar) to simulate subaerial and aerial hydrothermal conditions, respectively, on the early Earth. For these syntheses, the initial concentration of cyanide and the diffusion effects were studied. In addition, it is well known that hydrolysis conditions are directly related to the amount and diversity of organic molecules released from cyanide polymers. Thus, as a first step, we studied the effect of several hydrolysis procedures, generally used in prebiotic chemistry, on some of the potential pre-RNA nucleobases of interest, together with some of their isomers and/or deamination products, also presumably formed in these complex reactions. The results show that the alkaline hydrothermal scenarios with a relatively constant pH are good geological scenarios for the generation of noncanonical nucleobases using cyanide as a prebiotic precursor.

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Section: Discussionsupporting

confidence: 74%

Prebiotic synthesis of noncanonical nucleobases under plausible alkaline hydrothermal conditions

Pérez-Fernández

Vega

Rayo-Pizarroso

et al. 2022

Sci Rep

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“…If it were present in the Earth's prebiotic atmosphere, it could have been a key intermediate for purine and nucleoside formation pathways in the transition between prebiotic chemistry and the pre-RNA world. 4,8,9 Hence, its formation and detection in planetary atmospheres could significantly support the RNA-world hypothesis and confirm that the laboratory findings in prebiotic chemistry are consistent with the chemistry in actual planetary environments.…”

Section: ■ Introductionsupporting

confidence: 70%

Possible Gas-Phase Synthesis of Neutral Malononitrile (C₃H₂N₂) and Isocyanoacetonitrile (NCCH₂NC) under the Upper Atmospheric Conditions of Titan

Ramal-Olmedo,

Menor-Salván,

Miyoshi

et al. 2023

ACS Earth Space Chem.

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Malononitrile (C3H2N2) is a highly reactive compound that plays an important role in the synthesis of heterocyclic compounds and may have contributed to the formation of nucleobases and nucleosides in a pre-RNA world. Despite its significance in prebiotic chemistry and potential implications in astrobiology, its possible synthesis has not yet been documented. To date, the search for malononitrile in outer space has been unsuccessful, but the atmospheric conditions and abundance of carbonitrile compounds detected in Titan’s atmosphere suggest that this celestial body could be a conducive environment for its formation and existence. The purpose of this publication is to examine the feasibility of the gas-phase synthesis of malononitrile under the physical conditions present in the upper atmosphere of Titan, using chemical species detected or predicted in that atmosphere as reactants. We propose 62 initial gas-phase reaction mechanisms for synthesizing C3H2N2. Molecular energies are computed at the CCSD(T)-F12/cc-pVTZ-F12 and MP2/aug-cc-pVDZ levels of theory, and thermodynamic function values are calculated using the Maxwell–Boltzmann quantum theory. A benchmarking study of 14 DFT methods is conducted to identify the best geometry response that matched the reference (CCSD(T)-F12) under both room and Titan’s upper atmosphere pressure and temperature profiles. To identify the most kinetically favorable reaction mechanisms for malononitrile, VTST theory and RRKM simulations are performed across a range of temperatures (80–200 K) and pressures (9.87 × 10–10 to 2.0 atm). The most favorable reaction for the production of malononitrile is R8 (1HCCN + 1HNC) with a rate coefficient of 1.08 × 10–11 cm3 molecule–1 s–1, at 145 K and 9.87 × 10–10 atm and a modified Arrhenius expression of k = 1.65 × 10–11 ± 0.005(T/300)0.005 exp(−64.46/T) cm3 molecule–1 s–1. Chemical models predict that singlet 1HCCN should exist in the upper atmosphere of Titan, while HNC has already been detected there. Some of the proposed reaction mechanisms lead to isocyanoacetonitrile (NCCH2NC) as a product. The most probable formation mechanism for it is R2 (C2N2 + 1CH2) with a rate coefficient of 1.20 × 10–10 cm3 molecule–1 s–1 for the described pressure and temperature profiles with a modified Arrhenius expression of k = 4.48 × 10–15 ± 0.017(T/300)1.862 exp–(−42.44/T) cm3 molecule–1 s–1. The Cassini mission has directly identified both reactants, C2H2 and HCN, providing clear evidence of their presence. Our results further suggest that isocyanoacetonitrile may be roughly 1 order of magnitude more abundant than malononitrile assuming sufficient abundances of 1CH2.

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“…Beyond the nucleobases identified (uracil ( h9 ), adenine ( h15 ) and guanine ( h16 )), it is interesting to detect new triazines and pyrimidines, since recently cyanuric acid ( h5 ), barbituric acid ( h12 ), melamine and 2,4,6-triaminopyrimidine have been proposed as no canonical nucleobases in a pre-RNA world due to their capability to form ribonucleosides and supramolecular assemblies that are held by Watson–Crick type hydrogen-bonded base pairs. These heterocycles can be formed from cyanamide, its derivatives (malonic acid and urea) and AMN 49 , 50 . All of these N-heterocycle precursors are known to be formed from HCN 13 .…”

Section: Discussionmentioning

confidence: 99%

A dual perspective on the microwave-assisted synthesis of HCN polymers towards the chemical evolution and design of functional materials

Hortal

Pérez-Fernández

Fuente

et al. 2020

Sci Rep

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In this paper, the first study on NH4CN polymerization induced by microwave radiation is described, where a singular kinetic behaviour, especially when this reaction is conducted in the absence of air, is found. As a result, a complex conjugated N-heterocyclic polymer system is obtained, whose properties are very different, and even improved according to morphological features, characterized by their X-ray diffraction patterns and scanning electron microscopy analysis, with respect to those produced under conventional thermal treatment. In addition, a wide variety of relevant bioorganics have been identified, such as amino acids, nucleobases, co-factors, etc., from the synthetized NH4CN polymers. These particular families of polymers are of high interest in the fields of astrobiology and prebiotic chemistry and, more recently, in the development of smart multifunctional materials. From an astrobiological perspective, microwave-driven syntheses may simulate hydrothermal environments, which are considered ideal niches for increasing organic molecular complexity, and eventually as scenarios for an origin of life. From an industrial point of view and for potential applications, a microwave irradiation process leads to a notable decrease in the reaction times, and tune the properties of these new series macromolecular systems. The characteristics found for these materials encourage the development of further systematic research on this alternative HCN polymerization.

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Radical pathways for the formation of non-canonical nucleobases in prebiotic environments

Abstract: The study explores radical-assisted formations of the nucleobase components of primitive genetics from cyanamide and related precursors in impact events.

Cited by 7 publications

References 45 publications

Prebiotic synthesis of noncanonical nucleobases under plausible alkaline hydrothermal conditions

Prebiotic synthesis of noncanonical nucleobases under plausible alkaline hydrothermal conditions

Possible Gas-Phase Synthesis of Neutral Malononitrile (C₃H₂N₂) and Isocyanoacetonitrile (NCCH₂NC) under the Upper Atmospheric Conditions of Titan

A dual perspective on the microwave-assisted synthesis of HCN polymers towards the chemical evolution and design of functional materials

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Radical pathways for the formation of non-canonical nucleobases in prebiotic environments

Abstract: The study explores radical-assisted formations of the nucleobase components of primitive genetics from cyanamide and related precursors in impact events.

Cited by 7 publications

References 45 publications

Prebiotic synthesis of noncanonical nucleobases under plausible alkaline hydrothermal conditions

Prebiotic synthesis of noncanonical nucleobases under plausible alkaline hydrothermal conditions

Possible Gas-Phase Synthesis of Neutral Malononitrile (C3H2N2) and Isocyanoacetonitrile (NCCH2NC) under the Upper Atmospheric Conditions of Titan

A dual perspective on the microwave-assisted synthesis of HCN polymers towards the chemical evolution and design of functional materials

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Possible Gas-Phase Synthesis of Neutral Malononitrile (C₃H₂N₂) and Isocyanoacetonitrile (NCCH₂NC) under the Upper Atmospheric Conditions of Titan