The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, which were one order of magnitude more abundant during the LHB period than before and after, could not only destroy the existing ancient life forms, but could also contribute to the creation of biogenic molecules.

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 NH 3 + 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. The following explorations showed that a broad array of amino acids could be synthesized, but there was no evidence that all of the fundamental molecules of the RNA genetic code could be produced alongside others in this type of experiment (2-5). Additionally, the significant persistence of reducing atmospheres in a geological timescale has been seriously debated (6). Finally, many scientists have claimed that this experiment is not related to early-Earth conditions and does not provide fundamental building blocks (i.e., nucleobases) important for the evolution of early life possibly based on RNA (7-13). In 2001, Saladino, Di Mauro, and coworkers (14) proposed that the parent molecule for the one-pot synthesis of nucleobases is formamide (15-23). Their team, together with other authors, demonstrated the formation of (not only) fundamental nucleobases for the origin of RNA in experiments involving the heating of formamide in presence of manifold catalysts (17,(24)(25)(26), upon UV irradiation (27), proton (28) and heavy-particle radiation (29), exposition to shock waves (18), etc. Recently, Hörst et al. (30) also referred to a positive result on qualitative detection of RNA nucleobases and manifold amino acids from tholines created in a N 2 , CH 4 , CO mixture. Their experiment simulated the atmosphere of Titan upon electric discharge. Such experimental results as well as theoretical expectations (31) show that reduced, relatively reactive atmospheres are likely to be more efficient for the synthesis of biomolecules (32). However, it should be noted that several papers report also the formation of biomolecules under neutral (N 2 , CO 2 , H 2 O) conditions (33-35). In our study, we found an interconnection between the original ideas of the pioneering Miller-Urey studies devoted to prebiotic synthesis in a reducing atmosphere and recent results identifying the chemistry of formamide as a source for the synthesis of nucleobases. In addition to traditional hydrogen cyanide (HCN)-based or reducing atmosphere-based concept...

Aims To characterize the volatile metabolites produced by genotypically diverse strains of Pseudomonas aeruginosa in order to evaluate their potential for use as biomarkers of lung infection in noninvasive breath analysis. Methods and Results Volatile organic compounds (VOCs) emitted from 36 clinical strains of Ps. aeruginosa (belonging to different multilocus sequence types) cultured in liquid and on solid media were analysed by gas chromatography mass spectrometry (GC‐MS) and selected ion flow tube mass spectrometry (SIFT‐MS). Several previously identified VOCs were detected, including ethanol, acetone, 2‐butanone, 2‐pentanone, isoprene, aminoacetophenone, dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide and methyl thiocyanate. Additionally, significant production of 3‐methyl‐butanone, acetophenone, methylthioacetate and methyl thiobutanoate was observed for the first time in this study. SIFT‐MS quantifications of VOCs showed high variability between genotypically distinct strains. Conclusions The data obtained indicate that the production rates of the volatile biomarkers of Ps. aeruginosa vary by two orders of magnitude between different strains cultured under the same conditions. Similar variability was observed for both liquid and solid media. Significance and Impact of the Study Inter‐strain genotypic variability strongly influences the concentrations of the volatile biomarkers from Ps. aeruginosa. A group of several biomarkers quantified in real time in exhaled breath may thus provide a more valuable indicator of the course of pulmonary infections compared to a single biomarker.

Infection by Pseudomonas aeruginosa (PA) is a major cause of morbidity and mortality in patients with cystic fibrosis (CF). Breath analysis could potentially be a useful diagnostic of such infection, and analyses of volatile organic compounds (VOCs) emitted from PA cultures are an important part of the search for volatile breath markers of PA lung infection. Our pilot experiments using solid-phase microextraction, SPME and gas chromatography/mass spectrometric (GC/MS) analyses of volatile compounds produced by PA strains indicated a clear presence of methyl thiocyanate. This provided a motivation to develop a method for real-time online quantification of this compound by selected ion flow tube mass spectrometry, SIFT-MS. The kinetics of reactions of H(3)O(+), NO(+) and O(2)(+•) with methyl thiocyanate at 300 K were characterized and the characteristic product ions determined (proton transfer for H(3)O(+), rate constant 4.6 × 10(-9) cm(3) s(-1); association for NO(+), 1.7 × 10(-9) cm(3) s(-1) and nondissociative charge transfer for O(2)(+•) 4.3 × 10(-9) cm(3) s(-1)). The kinetics library was extended by a new entry for methyl thiocyanate accounting for overlaps with isotopologues of hydrated hydronium ions. Solubility of methyl thiocyanate in water (Henry's law constant) was determined using standard reference solutions and the linearity and limits of detection of both SIFT-MS and SPME-GC/MS methods were characterized. Thirty-six strains of PA with distinct genotype were cultivated under identical conditions and 28 of them (all also producing HCN) were found to release methyl thiocyanate in headspace concentrations greater than 6 parts per billion by volume (ppbv). SIFT-MS was also used to analyze the breath of 28 children with CF and the concentrations of methyl thiocyanate were found to be in the range 2-21 ppbv (median 7 ppbv).

The formation of nucleobases from formamide during a high-energy density event, i.e., the impact of an extraterrestrial body into the planetary atmosphere, was studied by irradiation of formamide ice and liquid samples with a high-power laser in the presence of potential catalysts. FTIR spectroscopy, time-resolved emission spectroscopy, and GC-MS were subsequently used to monitor the dissociation of this molecule into stable molecular fragments (HCN, H2O, HNCO, H2, CO, and NH3) and unstable species (HNC, •CN, and •NH). The kinetic and thermodynamic models of the high-energy density event molecular dynamics have been suggested together with the reaction routes leading from the dissociation products to the nucleobases. In addition, using theoretical calculations, we propose a simple new reaction pathway for the formation of both pyrimidine and purine nucleobases involving •CN radical chemistry.