Insights into the nature of the hydrogen bonding of {radical dot}Tyr272 in apo-galactose oxidase

Laurent Benisvy, Deborah Hammond, David J. Parker, E. Stephen Davies, C. David Garner, Jonathan McMaster, Claire Wilson, Frank Neese, Eberhard Bothe, Robert Bittl, Christian Teutloff

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9 Scopus citations


The synthesis and structure of an o-methylthio-phenol-imidazole, 2-(2′-(4′-tert-butyl-6′-methylsulfanyl)-hydroxyphenyl))-4,5-diphenyl-imidazole (MeSLH), is reported; X-ray crystallographic studies have shown that MeSLH involves an O-H···N+ hydrogen bond between the phenol and an imidazole nitrogen. MeSLH undergoes a reversible, one-electron, oxidation to form the radical cation [MeSLH]{radical dot}+ the EPR spectrum of which is remarkably similar to that of {radical dot}Tyr272 in Cu-free, oxidized, apo-GO. Density Functional Theory calculations, have shown that the proton-transferred (R-O{radical dot}···H-N+) form of [MeSLH]{radical dot}+ has a spin density distribution - with a substantial delocalization of the unpaired electron spin density onto the ortho sulfur atom - and EPR properties that are in good agreement with those of {radical dot}Tyr272 in Cu-free, oxidized, apo-GO whereas the non-proton-transferred (R-O{radical dot}+-H···N) form does not. The results reported herein are a further demonstration of the influence of hydrogen bonding on the nature and properties of phenoxyl radicals and strongly suggest that the phenoxyl oxygen of {radical dot}Tyr272 in Cu-free, oxidized, apo-GO is involved in a O{radical dot}···H-O/N hydrogen bond.

Original languageEnglish
Pages (from-to)1859-1864
Number of pages6
JournalJournal of Inorganic Biochemistry
Issue number11-12
StatePublished - Nov 2007
Externally publishedYes

Bibliographical note

Funding Information:
The authors thank Miss Petra Höfer for technical assistance and Dr. Sebastian Sinnecker for help with the electronic structure calculations. This work has been supported by the Engineering and Physical Sciences Research Council, UK (GR/R50325/01) and Deutsche Forschungsgemeinschaft (Sfb 498 TP C5). Dr. L. Benisvy thanks the Max-Planck Gesellschaft for the award of a postdoctoral fellowship.


  • Density functional calculations
  • EPR spectroscopy
  • Electronic structure
  • Hydrogen bond
  • Oxidized apo-galactose oxidase
  • Thioether phenoxyl radical


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