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Updated: Aug 21, 2026

Monitoring Equilibrium Changes in RNA Structure by 'Peroxidative' and 'Oxidative' Hydroxyl Radical Footprinting
Published on: October 17, 2011
Hydroxyl radical oxidation of cytochrome c by aerobic radiolysis
Benedicta N Nukuna1, Gang Sun, Vernon E Anderson
1Department of Biochemistry, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4935, USA.
Abstract:
The reaction of radiolytically generated *OH with cytochrome c was investigated by mass spectrometry. Tryptic digestion and characterization of the oxidized peptides by MALDI-TOF and ESI tandem mass spectrometry identified eight different amino acid residues with oxidized side chains with no cleavage of the protein detected. Solvent-accessible aromatic and methionine residues are the most susceptible to oxidation by *OH. These results support the careful use of *OH in characterizing protein surfaces. Dose-response studies identified the residues most prone to oxidation to be Phe-36, Phe-46, and Met-80. Hydroxylation of Phe-36 and Phe-46 should serve as indicators of the presence of *OH in the mitochondrial intermembrane space. Using solutions containing 50 at.% (18)O, our study also provides a novel method of determining the source of oxygen during *OH-mediated oxidation of proteins and contributes to identification of the modified residue type, with Phe>Tyr>Met in (18)O incorporation. During aerobic radiolysis, UV-vis spectroscopy indicates that ferrocytochrome c reaches a steady state concomitant with reduction of the heme.
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