International Journal of Quantum Chemistry, ( ISI ), Volume (112), No (14), Year (2012-1) , Pages (2675-2680)

Title : ( The Influence of Hydrophobic Amino Acid Side Groups on the Acidity of the Aromatic Imidazole Ring of Histidine: A Theoretical Study )

Authors: Reza Izadi Najafabadi , Mohammad Reza Housaindokht , mohammadsadegh sadeghi googheri , Mohsen Sargolzaei , Mohammad Izadyar ,

Access to full-text not allowed by authors

Citation: BibTeX | EndNote

In this study we have calculated the acidity constant (pKa) of imidazole ring in Histidine-Hydrophobic amino acid dipeptides using the quantum chemistry and continuum solvation methods. Density functional theory calculations with the large basis sets are used to determine the Gibbs free energy of deprotonate in the gas and liquid phases. Based on our results DGS values are located between 69.38 and 18.82 kcal mol 1 which are related to His þ –Gly and His forms, respectively. pKa of the dipeptides in the aqueous phase was obtained from the calculated gas-phase and solvation free energies through a thermodynamic cycle and the solvation model chemistry of Martin Karplus et al. Solvation effects are treated using a selfconsistent reaction field formalism involving polarized continuum models. According to our calculations pKa values are between 5.50 and 8.19 that are belong to His þ –ILe and His þ –Ala forms, respectively. Natural bond orbital analysis of dipeptides reveals that the electron delocalization in imidazole ring is the most effective factor in determination of acidity order for these compounds. Structural analysis confirmed that the orientation of carbonyl group with respect to imidazole ring is an effective factor in imidazole ring stability.

Keywords

, histidine , acidity constant , ab initio, solvation free energy, density functional theory, natural bond
برای دانلود از شناسه و رمز عبور پرتال پویا استفاده کنید.

@article{paperid:1025320,
author = {Izadi Najafabadi, Reza and Housaindokht, Mohammad Reza and Sadeghi Googheri, Mohammadsadegh and Sargolzaei, Mohsen and Izadyar, Mohammad},
title = {The Influence of Hydrophobic Amino Acid Side Groups on the Acidity of the Aromatic Imidazole Ring of Histidine: A Theoretical Study},
journal = {International Journal of Quantum Chemistry},
year = {2012},
volume = {112},
number = {14},
month = {January},
issn = {0020-7608},
pages = {2675--2680},
numpages = {5},
keywords = {histidine ; acidity constant ; ab initio; solvation free energy; density functional theory; natural bond orbital},
}

[Download]

%0 Journal Article
%T The Influence of Hydrophobic Amino Acid Side Groups on the Acidity of the Aromatic Imidazole Ring of Histidine: A Theoretical Study
%A Izadi Najafabadi, Reza
%A Housaindokht, Mohammad Reza
%A Sadeghi Googheri, Mohammadsadegh
%A Sargolzaei, Mohsen
%A Izadyar, Mohammad
%J International Journal of Quantum Chemistry
%@ 0020-7608
%D 2012

[Download]