Article (Scientific journals)
Charge transfer study through the determination of the ionization energies of tetrapeptides X3-Tyr, X = Gly, Ala, or Leu. Influence of the inclusion of one glycine in alanine and leucine containing peptides
Dehareng, Dominique; Dive, Georges
2006In Journal of Physical Chemistry. A, 110 (43), p. 11975-11987
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Keywords :
excited states energies; tetrapeptide radical cations; ab initio calculations
Abstract :
[en] The energies of the fundamental and several excited states of tetrapeptide radical cations were determined at the outer valence Green's function (OVGF) level, at three geometries corresponding to the lowest energy conformations: two for the neutral and one for the cation. The conformations were optimized at the density functional theory level within the B3LYP framework. It was found that, from a purely energetic point of view, a charge initially created on the tyrosine chromophore could migrate without any geometrical change and without further activation once the excited electronic state of the ionized chromophore was formed. This migration could reach the NH2 terminus for the neutral conformations but should stop at the adjacent peptide link for the cation conformation. These results stress the probable influence of the electronic coupling between the states rather than the existence of a barrier on the charge pathway to explain the difference between the peptides in the charge-transfer process leading to the loss of an iminium [NH2 = CHR](+) cation. The dissociation energy of the asymptote related to the formation of this NH2 terminus iminium cation was calculated for few species and it appears that the excess energy available for dissociation is significant when starting from the lowest energy conformations of the neutral or the cation, provided that the charge transfer is effective. It was also found that the amino acids did not conserve their energetic properties and their zero order energy levels turned to a complete new energetic scheme corresponding to the conformation of the peptide.
Disciplines :
Physics
Chemistry
Author, co-author :
Dehareng, Dominique ;  Université de Liège - ULiège > Centre d'ingénierie des protéines
Dive, Georges ;  Université de Liège - ULiège > Centre d'ingénierie des protéines
Language :
English
Title :
Charge transfer study through the determination of the ionization energies of tetrapeptides X3-Tyr, X = Gly, Ala, or Leu. Influence of the inclusion of one glycine in alanine and leucine containing peptides
Publication date :
02 November 2006
Journal title :
Journal of Physical Chemistry. A
ISSN :
1089-5639
eISSN :
1520-5215
Publisher :
Amer Chemical Soc, Washington, United States - Washington
Volume :
110
Issue :
43
Pages :
11975-11987
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 05 January 2009

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