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 H 2 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.
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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.