Potential formation of three pyrimidine bases in interstellar regions

Abstract

Work on the chemical evolution of pre-biotic molecules remains incomplete since the major obstacle is the lack of adequate knowledge of rate coefficients of various reactions which take place in interstellar conditions. In this work, we study the possibility of forming three pyrimidine bases, namely, cytosine, uracil and thymine in interstellar regions. Our study reveals that the synthesis of uracil from cytosine and water is quite impossible under interstellar circumstances. For the synthesis of thymine, reaction between uracil and : CH 2 is investigated. Since no other relevant pathways for the formation of uracil and thymine were available in the literature, we consider a large gas-grain chemical network to study the chemical evolution of cytosine in gas and ice phases. Our modeling result shows that cytosine would be produced in cold, dense interstellar conditions. However, presence of cytosine is yet to be established. We propose that a new molecule, namely, C 4 N 3 OH 5 could be observable in the interstellar region. C 4 N 3 OH 5 is a precursor (Z isomer of cytosine) of cytosine and far more abundant than cytosine.We hope that observation of this precursor molecule would enable us to estimate the abundance of cytosine in interstellar regions. We also carry out quantum chemical calculations to find out the vibrational as well as rotational transitions of this precursor molecule along with three pyrimidine bases.

Identification of Methyl Isocyanate and Other Complex Organic Molecules in a Hot Molecular Core, G31.41+0.31

“…The presence of a large number of COMs, including branched chain molecule might be an indication of the existence of prebiotic molecules and essential building blocks of life in space (Belloche et al 2014;Chakrabarti et al 2015;Majumdar et al 2015;Sil et al 2018;Sahu et al 2020). Goesmann et al (2015) detected various COMs (e.g., methyl isocyanate, formamide, glycolaldehyde, ethylamine etc.)…”

Quantum Chemical Study on Interstellar Synthesis of Cytosine by the Automated Reaction Path Search

“…Wang et al 2012 16 evaluated reactions between :CCCO and :CCCNH radicals with urea as the interstellar synthesis of uracil and cytosine, respectively. Moreover, in Majumdar et al 2015 17 , the possible formation of pyrimidine bases in interstellar regions was estimated by quantum chemistry and gas-grain chemical network calculations. As a result, the cytosine would generate in cold conditions, and C 4 N 3 OH 5 was proposed as a precursor of cytosine.…”

Identification of pre-biotic molecules containing Peptide-like bond in a hot molecular core, G10.47+0.03

“…Among them several ankan.das@gmail.com prasanta.astro@gmail.com species are marked as the precursor to biomolecules. Study of the pre-biotic molecules is always fascinating as they involved in the formation of amino acids, proteins, and the basic building blocks of life (Chakrabarti & Chakrabarti 2000a,b;Das et al 2008;Garrod 2013;Chakrabarti et al 2015;Majumdar et al 2015;Das et al 2019). Protein synthesis occurs through peptide bond formation (Goldman et al 2010).…”