Computational Study on the Interstellar Formation of Glycine

Computational Study on the interstellar formation of Glycine.

Zanele Nhlabatsi, Priya Bhasi, Sanyasi Sitha*.

Department of Chemistry, University of Johannesburg, P. O. Box 524, Auckland, Johannesburg, South Africa, 2006, SA.

Abstract.

The origin of homochirality and its role in the evolution of life in our solar system are the two most simulating questions, which are not yet answered exclusively [1,2,3]. For the first time, using computational calculations with various methods like, B3LYP, X3LYP, B3PW91, HF, O3LYP, CBSQB3, MP2, MP2(Full) and also various composite methods which are known for accurate energy predictions, like, G3, G3B3, G3MP2, G3MP2B3, we have shown an uncommon and well-defined termolecular reactions which can lead to the formation of interstellar glycine; the simplest amino acid. As the reaction proceeds through a concerted type of mechanism, we have argued on how such a mechanism can be exploited further to explain the enantiomeric excess found in meteoritic samples [4]. Moreover, we have also discussed the feasibility of such a reaction in high temperature as well as in low temperature conditions. Also proposed schemes for the formation of other alpha-amino acids, where the chirality preference can be tested. As tri-molecular reactions are kinetically less probable, so, on the basis of excess reactant consideration and sufficiency of the H2 as well as CO2 in the interstellar medium, we have attempted to show how this reaction can be further reduced to a pseudo bimolecular or even a pseudo uni-molecular type.

Mechanism: Tri-molecular NHCH2 + CO2 + H2 → NH2CH2COOH reaction that leads to the formation of glycine in the interstellar medium (ISM).

References.

[1] Palazzetti F, Marciel GS, Lombardi A, Grossi G, Aquilanti V: The Astronomical Observatory: Molecules in the Laboratory and in the Cosmos. J Chin Chem Soc 2012, 59:1045-1052.

[2] Deamer DW, Dick R, Thiemann W, Shinitzey M: Intrinsic Asymmetries of Amino Acids Enantiomers and their Peptides: A Possible Role in the Origin of Biochirality. Chirality 2007, 19:751-763.

[3] Lee T, Lin YK: The Origin of Life and Crystallization of Aspartic Acid in Water. Growth Des, 2010, 10:1652-1660.

[4] Levine M, Kenesky CS, Mazori D, Breslow R: Enantioselective Synthesis and Enantiomeric Amplification of Amino Acids under Prebiotic Conditions. Org Lett, 2008, 10:2433-2436.