ESR Spin-Trapping Studies of Free Radicals Generated by Hydrogen Peroxide Activation of Metmyoglobin

The reaction of metmyoglobin (MetMb) with hydrogen peroxide (H 2 O 2 ) generated a free radical that was detectable by ESR at room temperature only in the presence of the spin trap 5,5-dimethyl-1-pyrroline-N-oxyl (DMPO). The formation of the free radical was favored at pH≥7 and was depressed at low pH. The free radical spin-trapped by DMPO may be a ferryl radical or an amino acid free radical originating from the myoglobin moiety