Acetylenic/cyanoacetylenic complexes: simulation of the Titan’s atmosphere chemistry

On the Evolutionary History of the Twenty Encoded Amino Acids

α-Amino acids are essential molecular constituents of life, twenty of which are privileged because they are encoded by the ribosomal machinery. The question remains open as to why this number and why this 20 in particular, an almost philosophical question that cannot be conclusively resolved. They are closely related to the evolution of the genetic code and whether nucleic acids, amino acids, and peptides appeared simultaneously and were available under prebiotic conditions when the first self-sufficient complex molecular system emerged on Earth. This report focuses on prebiotic and metabolic aspects of amino acids and proteins starting with meteorites, followed by their formation, including peptides, under plausible prebiotic conditions, and the major biosynthetic pathways in the various kingdoms of life. Coenzymes play a key role in the present analysis in that amino acid metabolism is linked to glycolysis and different variants of the tricarboxylic acid cycle (TCA, rTCA, and the incomplete horseshoe version) as well as the biosynthesis of the most important coenzymes. Thus, the report opens additional perspectives and facets on the molecular evolution of primary metabolism.

Infrared study of matrix-isolated ethyl cyanide: simulation of the photochemistry in the atmosphere of Titan

Low-temperature Ar matrix isolation has been carried out to investigate the infrared spectrum of ethyl cyanide (CH₃CH₂CN), a molecule present in the atmosphere of Titan.

An ab initio computational study of thiamin synthesis from gaseous reactants of the interstellar medium

A set of chemical reactions is proposed to account for the formation of thiamin derivatives from gaseous reactants that have been identified in the interstellar medium, and may have been relevant to a prebiotic atmosphere. The gaseous mixture consisted of methanimine, acetonitrile, cyanoacetylene, ammonia, acetylene, allylene, hydrogen sulfide, thioformaldehyde, and hydrogen in the presence of water. Most of the reactions appear to be exothermic. The reactions have been shown to be feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2/6-31G(*) level.

Photochemical Synthesis of the Cyanodiacetylene HC5N: A Cryogenic Matrix Experiment

The reactivity of intermolecular complexes cyanoacetylene:acetylene and dicyanoacetylene:acetylene, trapped in solid argon matrixes at 10 K and irradiated with vacuum UV, has been studied. FTIR measurements, together with (2)H, (15)N, (13)C labeling experiments and with density functional theory (DFT) calculations (B3LYP/aug-cc-pVTZ), pointed to the formation of cyanodiacetylene HC(5)N (cyanobutadiyne). This synthetic route is potentially important for chemical models of the Titan's atmosphere.