ESR study of the non-enzymic scission of xyloglucan by an ascorbate-H2O2-copper system: the involvement of the hydroxyl radical and the degradation of ascorbate

G Tabbi, S C Fry, R P Bonomo

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Abstract

Xyloglucan is degraded by a mixture of copper(II). hydrogen peroxide and ascorbate. In the presence of ascorbate and/or hydrogen peroxide, copper(II) species were rapidly reduced to copper(I), which react with hydrogen peroxide. Spin-trapping experiments showed that hydroxyl radicals formed and attacked xyloglucan causing its degradation. The formation of a carbon-centred ascorbyl (C-ascorbyl) radical and its degradation with the formation of oxalate, was also caused by hydroxyl radicals. As a consequence, the features of the bis(oxalate) copper(II) complex clearly appeared in the frozen solution ESR spectra. The formation of carbon-centred radicals on the xyloglucan is the trigger for a series of possible molecular rearrangements which led to its oxidative scission. (C) 2001 Elsevier Science B.V. All rights reserved.

Original languageEnglish
Pages (from-to)179-187
Number of pages9
JournalJournal of Inorganic Biochemistry
Volume84
Issue number3-4
Publication statusPublished - Apr 2001

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