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Titolo:
Glutathione radical: Intramolecular H abstraction by the thiyl radical
Autore:
Rauk, A; Armstrong, DA; Berges, J;
Indirizzi:
Univ Calgary, Dept Chem, Calgary, AB T2N 1N4, Canada Univ Calgary CalgaryAB Canada T2N 1N4 Chem, Calgary, AB T2N 1N4, Canada Univ Paris 06, Chim Theor Lab, F-75252 Paris 05, France Univ Paris 06 Paris France 05 , Chim Theor Lab, F-75252 Paris 05, France
Titolo Testata:
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE
fascicolo: 4, volume: 79, anno: 2001,
pagine: 405 - 417
SICI:
0008-4042(200104)79:4<405:GRIHAB>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
AMINO-ACID-RESIDUES; AB-INITIO; C-H; MOLECULAR-ENERGIES; OXIDATIVE DAMAGE; PULSE-RADIOLYSIS; AQUEOUS-SOLUTION; GAS-PHASE; PROTEINS; GLYCINE;
Keywords:
glutathione; thiyl radical; alpha-C-radical; hydrogen transfer;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Rauk, A Univ Calgary, Dept Chem, Calgary, AB T2N 1N4, Canada Univ CalgaryCalgary AB Canada T2N 1N4 algary, AB T2N 1N4, Canada
Citazione:
A. Rauk et al., "Glutathione radical: Intramolecular H abstraction by the thiyl radical", CAN J CHEM, 79(4), 2001, pp. 405-417

Abstract

Ab initio computations (B3LYP/6-31G(D)) were used to predict transition structures and energies of activation for intramolecular H atom transfer to athiyl radical (RS.) from the alpha -C-H bonds of glutathione (1) and from the model compounds, N-formylcysteinylglycine (2) and N-(2-thioethanyl)-gamma -glutamine (3). For each compound, transition structures were located byin vacuo calculations on the neutral non-zwitterionic system. Thermodynamic functions derived at the same level and single point calculations at the B3LYP/6-311+G(3df,2p) level, were used to derive free energies of activation (DeltaG(not equal)) and reaction (DeltaG degrees). For abstraction of thealpha -C-H (Gly) by the thiyl radical in the gas phase, DeltaG(not equal) = 134 kJ mol(-1) if the amide link to Gly is in the more stable (Z)-configuration, and DeltaG(not equal) = 52 kJ mol(-1) if it is in the less stable (E)-configuration. The isomerization of the amide group requires about 95 kJmol(-1). Previous studies had indicated that for intramolecular reaction of the thiyl radical at alpha -C-H (Cys), DeltaG(not equal) = 110 kJ mol(-1). The lowest energy pathway for intramolecular H-transfer to the thiyl radical is from alpha -C-H (Gln), DeltaG(not equal) = 37-42 kJ mol(-1), and corresponds rather well with experimental results in solution (DeltaG(not equal) = 43 kJ mol(-1)). The calculated free energy change for the equilibrium between thiyl and alpha -C forms of the glutathione radical is DeltaG degrees = -54 kJ mol(-1). The value estimated from experimental data is DeltaG degrees = -37 kJ mol(-1). The agreement between the energies from theory in the gas phase and experiment in solution suggests that the free energies ofsolvation of reactant thiyl radical, transition structures for H abstraction, and the product alpha -C-centred radical, are very similar. The effectsof solution were estimated by two continuum models (SCIPCM and COSMO). TheSCIPCM model yields results very similar to the gas phase, predicting a modest lowering of the activation free energy. The results from the COSMO method were inconclusive as to whether a rate enhancement or decrease could beexpected.

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Documento generato il 14/08/20 alle ore 16:16:11