July 8, 2022 (Nanowerk News) Nitriles, a class of organic molecules with a cyano group, that is, a carbon atom attached with a triple unsaturated bond to a nitrogen atom, are usually toxic. But, paradoxically, they are also a key precursor of molecules essential for life, such as ribonucleotides, composed of nucleobases or ‘letters’ A, U, C and G attached to a ribose and phosphate group, which together form the RNA. Now, a team of researchers from Spain, Japan, Chile, Italy and the US show that a wide range of nitriles is produced in interstellar space within the molecular cloud G + 0.693-0.027, near the center of the Milky Way (Frontiers in Astronomy). and Space Sciences, “Molecular Precursors of the RNA World in Space: New Nitriles in the G + 0.693-0.027 Molecular Cloud”). Dr. Víctor M. Rivilla, researcher at the Center for Astrobiology of the CSIC and the National Institute of Aerospace Technology (INTA) in Madrid, Spain, and first author of the new study, said: “Here we have shown that chemistry that takes place in the interstellar medium is able to efficiently form multiple nitriles, which are key molecular precursors of the “RNA World” scenario.
Possible “RNA only” world.
Under this scenario, life on Earth was originally based solely on RNA, and DNA and protein enzymes later evolved. RNA can perform both functions: storing and copying information such as DNA and catalyzing reactions such as enzymes. According to the “RNA World” theory, nitriles and other building blocks of life have not necessarily all emerged on Earth itself: they could also have originated in space and “hitchhiked” on Earth. young inside meteorites and comets during the “Final”. Intense bombing period, between 4.1 and 3.8 billion years ago. In support, nitriles and other nucleotide, lipid, and amino acid precursor molecules have been found within contemporary comets and meteors. But where could these molecules have come from in space? The main candidates are molecular clouds, which are dense, cold regions of the interstellar medium, and are suitable for the formation of complex molecules. For example, the molecular cloud G + 0.693-0.027 has a temperature of about 100 K and is about three light-years in diameter, with a mass about a thousand times that of our Sun. There is no evidence that stars are currently forming within G + 0.693-0.027, although scientists suspect it could evolve to become a stellar nursery in the future. “The chemical content of G + 0.693-0.027 is similar to that of other star-forming regions of our galaxy, and also to that of objects in the solar system such as comets. This means that their study can give us information. important about the chemical ingredients that were available in the nebula that give rise to our planetary system, ”Rivilla explained.
Electromagnetic spectra studied
Rivilla and his colleagues used two telescopes in Spain to study the electromagnetic spectra emitted by G + 0.693-0.027: the IRAM telescope 30 meters wide in Granada and the Yebes telescope 40 meters wide in Guadalajara. They detected the nitriles cyanoallene (CH2CCHCN), propargyl cyanide (HCCCH2CN) and cyanopropium, which had not yet been found at G + 0.693-0.027, although they had been reported in 2019 in the dark cloud TMC-1 in the constellations Taurus. and Auriga, a molecular cloud with very different conditions from G + 0.693-0.027. Rivilla et al. also found possible evidence of the appearance at G + 0.693-0.027 of cyanoformaldehyde (HCOCN) and glycolinitrile (HOCH2CN). Cyanoformaldehyde was first detected in the molecular clouds TMC-1 and Sgr B2 in the constellation Sagittarius, and glycolinitrile in the Sun-like protostar IRAS16293-2422 B in the constellation Ophiuchus. Other recent studies have also reported other RNA precursors within G + 0.693-0.027, such as glycolaldehyde (HCOCH2OH), urea (NH2CONH2), hydroxylamine (NH2OH), and 1,2-etenediol (C2H4O2), confirming that the Interstellar chemistry is able to provide the most basic ingredients for the “RNA World.”
Nitriles among the most abundant chemical families in space
The final author, Dr. Miguel A Requena-Torres, a professor at Towson University in Maryland, USA, concluded: “Thanks to our observations over the past few years, including current results, we now know that nitriles are found. “among the most abundant chemical families in the universe. We have found them in molecular clouds in the center of our galaxy, protostars of different masses, meteorites and comets, and also in the atmosphere of Titan, Saturn’s largest moon.” The second author, Dr. Izaskun Jiménez-Serra, also a researcher at the CSIC and INTA, looked ahead: “So far we have detected several simple ribonucleotide precursors, the basic components of RNA. But there are still molecules For example, we know that the origin of life on Earth probably also required other molecules such as lipids, which are responsible for the formation of the first cells, so we also need them. we need to focus on understanding how lipids could be formed from simpler precursors available in the interstellar medium. “