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  • Title: Insights into the nature of the hydrogen bonding of *Tyr272 in apo-galactose oxidase.
    Author: Benisvy L, Hammond D, Parker DJ, Davies ES, Garner CD, McMaster J, Wilson C, Neese F, Bothe E, Bittl R, Teutloff C.
    Journal: J Inorg Biochem; 2007 Nov; 101(11-12):1859-64. PubMed ID: 17826837.
    Abstract:
    The synthesis and structure of an o-methylthio-phenol-imidazole, 2-(2'-(4'-tert-butyl-6'-methylsulfanyl)-hydroxyphenyl))-4,5-diphenyl-imidazole ((MeS)LH), is reported; X-ray crystallographic studies have shown that (MeS)LH involves an O-H...N(+) hydrogen bond between the phenol and an imidazole nitrogen. (MeS)LH undergoes a reversible, one-electron, oxidation to form the radical cation [(MeS)LH](*)(+) the EPR spectrum of which is remarkably similar to that of (*)Tyr(272) in Cu-free, oxidized, apo-GO. Density Functional Theory calculations, have shown that the proton-transferred (R-O(*)...H-N(+)) form of [(MeS)LH](*)(+) 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 (*)Tyr(272) in Cu-free, oxidized, apo-GO whereas the non-proton-transferred (R-O(*)(+)-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 (*)Tyr(272) in Cu-free, oxidized, apo-GO is involved in a O(*)...H-O/N hydrogen bond.
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