Authors: Svistunenko, Dimitri A.; Reeder, Brandon J.; Wilson, Michael T.; Cooper, Chris E.

Source: Progress in Reaction Kinetics and Mechanism, Volume 28, Number 1, 2003 , pp. 105-118(14)

Publisher: Science Reviews 2000 Ltd

Abstract:

Three EPR signals from individual free radical species have been identified in the EPR spectra of horse heart metmyoglobin (HH metMb) mixed with hydrogen peroxide (H₂O₂). The peroxyl radical EPR signal was assigned to the Trp14-OO^* radical, the seven component signal ­ to the Tyr103^* radical and the singlet EPR signal was assigned to the Tyr146^* radical. Apo-Mb (haem free HH Mb) added in various concentrations to the native metMb prior to H₂O₂ addition affected the yields of the three types of radicals. As the concentrations of metMb and H₂O₂ were kept constant, the yield of the primary radical formed is the same in all experiments, H₂O₂ being unable to produce any radical in the reaction with a haem free protein. Nevertheless, the addition of apo-Mb resulted in an increase of the Tyr146^* radical concentration and in a quantitatively similar decrease of the Tyr103^* radical concentration. These changes were dependent on the concentration of the added apo-Mb. Thus we show that a radical transfer Tyr103^* * Tyr146^* occurs and that this reaction is protein concentration dependent. The question whether this radical transfer is inter- or intra-molecular is discussed. A similarity is drawn between the system studied and the sperm whale metMb/H₂O₂ system, for which the radical transfer Tyr103^* * Tyr151^* has been previously suggested.

Document Type: Research article

DOI: http://dx.doi.org/10.3184/007967403103165477

Publication date: 2003-03-01

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• Progress in Reaction Kinetics & Mechanism is an international journal for the quarterly publication of both in-depth reviews and research articles.

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