The conformational landscape of L-threonine: Matrix isolation infrared and ab-initio studies

Dubey, Pankaj

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https://hdl.handle.net/2142/96912 Copy

Description

Title

The conformational landscape of L-threonine: Matrix isolation infrared and ab-initio studies

Author(s)

Dubey, Pankaj

Contributor(s)

• Viswanathan, K.S.
• Mukhopadhyay, Anamika

Issue Date

2017-06-21

Keyword(s)

• Conformers
• Isomers
• Chirality
• Stereochemistry

Abstract

Amino acids, containing hydroxy side chains such as L-threonine and tyrosine play an important role in molecular recognition, such as in the docking of propofol, which is a commonly used anaesthetic. A rich conformational landscape of these amino acids makes them interesting candidates in the study of intra and intermolecular interactions. In this work, the conformational landscape of L-threonine was studied, as it can be expected to serve as a basis for understanding structure and functions of polypeptides and other biomolecules. The matrix isolation technique (MI) coupled with a high temperature effusive molecular beam (EMB) nozzle was used to trap conformers of amino acid, which were then characterized using FTIR spectroscopy. The usefulness of MI-EMB-FTIR spectroscopy is that it can trap structures corresponding to the local minima along with the global minimum and hence allows for a better exploration of the potential energy surface. A major challenge in conformational analysis of amino acids using matrix isolation FTIR arises from its non-volatile nature. A home built heating system which was mounted close to the cryotip, was used to evaporate the non-volatile amino acids. Our infrared spectra show that three conformations were trapped in the matrix. Experimental results were supported by textit {ab-initio} calculations performed using the CCSD(T), MP2 and M06-2X methods together with 6-311++G(d,p) and aug/cc-pVDZ basis sets. The side chains of the amino acids appeared to have an influence on the preferential stabilisation of a particular backbone structure of amino acids. Factors such as entropy, anomeric effect and intramolecular H-bonding were also found to play an important role in determining conformal preferences, which will be discussed.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/96912

DOI

https://doi.org/10.15278/isms.2017.WC06

Copyright and License Information

Copyright 2017 Pankaj Dubey

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