Direct Detection of Peroxyl Radicals Formed in the Reactions of Metmyoglobin and Methaemoglobin with t-butyl Hydroperoxide

Abstract

The reaction of metmyoglobin and methaemoglobin with t-butyl hydroperoxide has been investigated using stopped-flow e.s.r. spectroscopy. The major species observed immediately after mixing has been identified as the basis of its g value (2.014) and line width as being due to a peroxyl radical. The detection of this species under anaerobic conditions suggests that this species is the t-butyl peroxyl radical rather than a secondary species. The immediate observation of this species on mixing suggests that this species is arising via a reaction involving the intact haem moiety rather than via 'free iron' produced via oxidative damage. Detection of a second, oxygen-dependent, species, which is formed at a slower rate, in the metmyoglobin reaction suggests that the initial peroxyl radical subsequently reacts with the protein to give a protein-derived radical.

Key Words:

• Free radicals
• electron spin resonance
• peroxyl
• hydroperoxide
• metmyoglobin
• methaemoglobin