Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/203746

Title

Effects of alkyl side chains on properties of aliphatic amino acids probed using quantum chemical calculations

Author(s)

Ganesan, Aravindhan;  Wang, Feng;  Brunger, Michael;  Prince, Kevin

Abstract

Effects of alkyl side chains (R-) on the electronic structural properties of aliphatic amino acids are investigated using quantum mechanical approaches. The carbon (C 1s) binding energy spectra of the aliphatic amino acids are derived from the C 1s spectrum of glycine (the parent spectrum) by the addition of spectral peaks, depending on the alkyl side chains, appearing in the lower energy region IP < 290 eV (where IP is the ionization potential). The two glycyl parent spectral peaks of the amide 291.0 eV [C(2)] and carboxylic 293.5 eV [ (1)] C atoms are shifted in the aliphatic amino acids owing to perturbations depending on the size and structure of the alkyl chains. The pattern of the N 1s and O 1s spectra in glycine is retained in the spectra of the other amino acids with small shifts to lower energy, again depending on the alkyl side chain. The Hirshfeld charge analyses confirm the observations. The alkyl effects on the valence binding energy spectra of the amino acids are concentrated in the middle valence energy region of 12-16 eV, and hence this energy region of 12-16 eV is considered as the `fingerprint' of the alkyl side chains. Selected valence orbitals, either inside or outside of the alkyl fingerprint region, are presented using both density distributions and orbital momentum distributions, in order to understand the chemical bonding of the amino acids. It is also observed that the HOMO-LUMO energy gaps of the aliphatic amino acids are reduced with the growth of the alkyl side chain.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Life and Social Sciences

Source

Journal of Synchrotron Radiation, Vol. 18, no. 5 (Sep 2011), pp. 733-742

Publication year

2011

FOR Code(s)

0205 Optical Physics;  0306 Physical Chemistry (Incl. Structural)

Keyword(s)

Aliphatic amino acids;  Alkyl side chain effects;  Dual space analysis;  Ionization energy spectra;  Orbital momentum distributions

Publisher

Wiley-Blackwell Publishing

ISSN

0909-0495

Publisher URL

http://dx.doi.org/10.1107/s0909049511029499

Copyright

Copyright © 2011 International Union of Crystallography.

Peer reviewed