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Relative acidities of ortho-substituted phenols, as models for modified tyrosines in proteins
KTH, Superseded Departments, Biotechnology.
2002 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 106, no 37, 8757-8761 p.Article in journal (Refereed) Published
Abstract [en]

The effects of a variety of ortho-substituents (CH3, OH, OCH3, SH, SCH3, NH2, NO2, F, Cl, CN, and imidazole) on the acidity of phenol are investigated using hybrid density functional theory. Substitutions are made at the ortho-position to model modified tyrosine residues found in enzymes. Although the experimental trends are reproduced, the calculations tend to exaggerate the substituent effects. It is shown that the cysteine cross-link to tyrosine, present in the radical enzyme galactose oxidase, has a small effect on the pK(a) of the residue. The histidine cross-link present in cytochrome c oxidase, on the other hand, will contribute more to. lower the pKa. Comparing the substituent effects on the O-H bond strengths and the acidities, no simple correlation is found between the two.

Place, publisher, year, edition, pages
2002. Vol. 106, no 37, 8757-8761 p.
Keyword [en]
cytochrome-c-oxidase, bond-dissociation energies, galactose-oxidase, gas-phase, equilibrium acidities, carboxylic-acids, aqueous-solution, proton-transfer, active-site, solvent
URN: urn:nbn:se:kth:diva-21893ISI: 000178010400032OAI: diva2:340591
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

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