Synthesis of RNA nucleobases from formamide is one of the recurring topics of prebiotic chemistry research. Earlier reports suggest that thymine, the substitute for uracil in DNA, may also be synthesized from formamide in the presence of catalysts enabling conversion of formamide to formaldehyde. In the current paper, we show that to a lesser extent conversion of uracil to thymine may occur even in the absence of catalysts. This is enabled by the presence of formic acid in the reaction mixture that forms as the hydrolysis product of formamide. Under the reaction conditions of our study, the disproportionation of formic acid may produce formaldehyde that hydroxymethylates uracil in the first step of the conversion process. The experiments are supplemented by quantum chemical modeling of the reaction pathway, supporting the plausibility of the mechanism suggested by Saladino and coworkers.
Recent results in prebiotic chemistry implicate hydrogen cyanide (HCN) as the source of carbon and nitrogen for the synthesis of nucleotide, amino acid and lipid building blocks. HCN can be produced during impact events by reprocessing of carbonaceous and nitrogenous materials from both the impactor and the atmosphere; it can also be produced from these materials by electrical discharge. Here we investigate the effect of high energy events on a range of starting mixtures representative of various atmosphere-impactor volatile combinations. Using continuously scanning time-resolved spectrometry, we have detected ·CN radical and excited CO as the initially most abundant products. Cyano radicals and excited carbon monoxide molecules in particular are reactive, energy-rich species, but are resilient owing to favourable Franck-Condon factors. The subsequent reactions of these first formed excited species lead to the production of ground-state prebiotic building blocks, principally HCN.
The Miller-Urey experiments pioneered modern research on the molecular origins of life, but their actual relevance in this field was later questioned because the gas mixture used in their research is considered too reducing with respect to the most accepted hypotheses for the conditions on primordial Earth. In particular, the production of only amino acids has been taken as evidence of the limited relevance of the results. Here, we report an experimental work, combined with state-of-the-art computational methods, in which both electric discharge and laser-driven plasma impact simulations were carried out in a reducing atmosphere containing NH3 + CO. We show that RNA nucleobases are synthesized in these experiments, strongly supporting the possibility of the emergence of biologically relevant molecules in a reducing atmosphere. The reconstructed synthetic pathways indicate that small radicals and formamide play a crucial role, in agreement with a number of recent experimental and theoretical results.
Recent synthetic efforts aimed at reconstructing the beginning of life on our planet point at the plausibility of scenarios fueled by extraterrestrial energy sources. In the current work we show that beyond nucleobases the sugar components of the first informational polymers can be synthesized in this way. We demonstrate that a laser-induced high-energy chemistry combined with TiO2 catalysis readily produces a mixture of pentoses, among them ribose, arabinose and xylose. This chemistry might be highly relevant to the Late Heavy Bombardment period of Earth's history about 4-3.85 billion years ago. In addition, we present an in-depth theoretical analysis of the most challenging step of the reaction pathway, i.e., the TiO2-catalyzed dimerization of formaldehyde leading to glycolaldehyde.
- MeSH
- arabinosa chemická syntéza MeSH
- dimerizace MeSH
- formaldehyd chemie MeSH
- katalýza MeSH
- planetární evoluce MeSH
- původ života MeSH
- ribosa chemická syntéza MeSH
- sacharidy chemická syntéza MeSH
- titan chemie MeSH
- xylosa chemická syntéza MeSH
- Země (planeta) MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The end of the late heavy bombardment era coincides with the emergence of life on the Earth 4 billion years ago. This coincidence suggests that the impacts of extraterrestrial bodies might have contributed to the formation of the first molecules involved in early living structures. We have simulated a high-energy synthesis of nucleic acid bases from formamide in the impact of an extraterrestrial body. The high-power laser system PALS was employed in simulation of impact plasma by inducing a laser dielectric breakdown in formamide. In hot and dense plasma, formamide decomposed producing reactive radicals. The radicals reacted with formamide and nucleic acid bases were produced. Formamide was pretreated with laser plasma in the presence of catalysts. The products were analyzed by FTIR spectrometry and GC-MS. Time-resolved emission spectra of formamide discharge plasma were measured. Kinetic models and formation pathways for nucleic acid bases were calculated. The results show that the nucleic acid bases can be synthesized in impact plasma involving CN and NH radicals and formamide.
- MeSH
- biogeneze organel MeSH
- formamidy * chemie MeSH
- katalýza MeSH
- lasery využití MeSH
- nukleové kyseliny * chemie MeSH
- plynová chromatografie s hmotnostně spektrometrickou detekcí přístrojové vybavení MeSH
- spektroskopie infračervená s Fourierovou transformací přístrojové vybavení MeSH
- Země (planeta) MeSH
This work concerns the role of formaldehyde in the environment and describes the basic indoor and outdoor detection techniques. One of the laboratory techniques, laser photoacoustic spectroscopy, was used for detection of formaldehyde based on its absorption spectrum in a region around 4350 cm-1. A new type of diode laser (GaInAsSb/AlGaAsSb - MQW (Multi-quantum well)) operating at room temperature in combination with a simple resonance photoacoustic cell provides the minimum detectable signal of formaldehyde, ca. 1250 µg m-3, at 4356 cm-1.
