Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

Abstract

Liquid formamide has been irradiated by high-energy proton beams in the presence of powdered meteorites, and the products of the catalyzed resulting syntheses were analyzed by mass spectrometry. Relative to the controls (no radiation, or no formamide, or no catalyst), an extremely rich, variegate, and prebiotically relevant panel of compounds was observed. The meteorites tested were representative of the four major classes: iron, stony iron, chondrites, and achondrites. The products obtained were amino acids, carboxylic acids, nucleobases, sugars, and, most notably, four nucleosides: cytidine, uridine, adenosine, and thymidine. In accordance with theoretical studies, the detection of HCN oligomers suggests the occurrence of mechanisms based on the generation of radical cyanide species (CN·) for the synthesis of nucleobases. Given that many of the compounds obtained are key components of extant organisms, these observations contribute to outline plausible exogenous high-energy-based prebiotic scenarios and their possible boundary conditions, as discussed.origin of life | formamide | prebiotic syntheses | nucleosides | meteorites H ypothesizing formamide (FA) as parent molecule, we explored its potentiality in synthetic processes when exposed to proton irradiation. The purpose of this analysis is to verify a possible prebiotic scenario consisting of FA, considered here as starting one-carbon atom material, of proton beams mimicking solar energetic particles as energy source, and of meteorites as catalysts. The rationale of this approach is that the results could help in outlining exogenous prebiotic models and their boundaries.FA (NH 2 CHO) is becoming one of the most intensively studied precursors for prebiotic syntheses of compounds potentially relevant for the origin of life (1-4). FA is a ubiquitous molecule in the universe. It has been detected in galactic centers (Sgr A and Sgr B), in star-forming regions of dense molecular clouds, in high-mass young stellar objects, in the interstellar medium and in comets and satellites (5)(6)(7)(8)(9)(10)(11)(12)(13)(14).With the appropriate mineral as catalyst, different ensembles of intermediates of genetic and metabolic apparatuses are simultaneously synthesized from FA under thermal conditions (i.e., by heating liquid FA between 333 and 453 K at room pressure). DNA and RNA components (15-21), amino acids (22, 23), sugars (24), and carboxylic acids (25, 26) have been obtained. Minerals tune the selectivity of these transformations (1, 2), the mechanistic pathways for the synthesis of nucleobases requiring pyrimidine (27-30) or imidazole intermediates (31,32).Within the solar system, ionizing cosmic radiation is generated by the Sun [solar cosmic rays (SCRs), primarily protons accelerated by flares and coronal mass ejections to energies typically of tens to hundreds megaelectronvolts] and is also formed by particles coming from the deep universe [galactic cosmic rays (GCRs)] (33). The SCRs and GCRs differ in their components and energy spectra, but their overwhelming co...

Formamide reaction network in gas phase and solution via a unified theoretical approach: Toward a reconciliation of different prebiotic scenarios

“…Among such small organic molecules, formamide is assuming an ever more central role in prebiotic chemistry research, as recently shown in experiments mimicking some of those origins of life scenarios, such as laser sparks (6), UV light (7), proton irradiation (8), or shock waves (as in meteorite impacts) (9). The main reason for such strong interest in formamide, besides its ubiquitousness in the solar system, is its chemical flexibility: it can be formed from (or, conversely, dissociated into) different molecular species that represent fundamental building blocks, including H 2 , H 2 O, NH 3 , CO, HCN, HNCO, and HCOOH (10,11).…”

Stability of 2′,3′ and 3′,5′ cyclic nucleotides in formamide and in water: a theoretical insight into the factors controlling the accumulation of nucleic acid building blocks in a prebiotic pool

“…51 At around 430K in liquid formamide most of the prebiotic building blocks (i.e. nucleobases, nucleosides) can be synthesized, 7,8,[52][53][54] and, after phosphorylation (Ref. 5 ), they can accumulate in the form of nucleotides.…”

“…1,2 Their strained intramolecular phosphodiester linkage accumulates chemical energy which can be utilized to drive transphosphorylation reactions leading to oligonucleotides. 3 Recently, various plausible prebiotic pathways have been elaborated for their synthesis, [4][5][6] among which the one based on formamide 5,7,8 has been found to yield a mixture of both 2',3' and 3',5'-linked cyclic forms. Based on these experimental results it has been suggested that higher temperatures of the prebiotic environment favor accumulation of the 3',5' form over the 2',3' variant.…”

On the Plausibility of Pseudosugar Formation in Cometary Ices and Oxygen-rich Tholins

“…Obviously these premises do not exclude the prebiotic formation of similar structures in either watery environments or gas-rich atmospheres, even though the chemistry of dust grains and interstellar bodies seems to be largely dominated by surface and solid state reactions (Williams and Viti 2013). Furthermore, as reported recently, meteoritic samples (presumably containing tiny amounts of organics) can also catalyze the formation of numerous prebiotic molecules and analogs by irradiation with high-energy protons of formamide serving as versatile scaffold (Saladino et al 2015). …”