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Volume 24 (2010), Issue 3-4, Pages 219-232

Conformational analysis and vibrational spectroscopic investigation of L-alanyl-L-glutamine dipeptide

Serda Kecel,1,4 Aysen E. Ozel,1 Sevim Akyuz,2 and Sefa Celik3

1Faculty of Sciences, Department of Physics, Istanbul University, Istanbul, Turkey
2Faculty of Science and Letters, Department of Physics, Istanbul Kultur University, Atakoy Campus, Istanbul, Turkey
3Engineering Faculty, Department of Electrical-Electronics Engineering, Istanbul University, Avcilar, Istanbul, Turkey
4Faculty of Sciences, Department of Physics, Istanbul University, Vezneciler 34134, Istanbul, Turkey

Copyright © 2010 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In this study conformational behavior of anticancer chemotherapy dipeptide Ala-Gln and its dimers have been investigated by molecular mechanic and ab-initio calculations. The calculations on Ala-Gln dipeptide as a function of side chain torsion angles, enable us to determine their energetically preferred conformations. The relative positions of the side chain residues of the stable conformations of dipeptide were obtained, depending on the obtained conformational analysis results. The lowest energy conformation of the dipeptide has been determined by using the Ramachandran maps (Biopolymers 6 (1963), 1494; J. Mol. Biol.7 (1963), 95) and compared with the quantum chemical ab-initio results. The geometry optimization, vibrational wavenumbers and intensity calculations of Ala-Gln dipeptide were carried out with the Gaussian03 program by using DFT with B3LYP functional and 6-31++G(d,p) basis set. The IR (4000–400 cm−1) and Raman spectra of the Ala-Gln dipeptide have been reported in solid phase, and compared with the theoretical vibrational data.