Transitional metal ions induced damage to biomolecules: Role of ferryl and perferryl radicals

Objective: To investigate the effect of oxidized transitional metal (ferric and cupric) ions on the amino acids. Methods: 25 mmol/L hydroxyproline and 25 mmol/L histidine were incubated with 50 μL Fe³⁺ and Cu²⁺ ions at pH 7.4 and 37 °C for 30 mins in separate test tubes. Then 500 μL of 1% thiobarbituricacid (TBA) was added to the incubated amino acids followed by addition of 500 μL of glacial acetic acid. The resultant mixture was vortexed and heated at 100 °C for 30 min. Absorbance readings were noted after cooling to room temperature. The experiment was repeated in the presence of various reagents, like hydroxyl radical scavengers, antioxidant enzymes, and reducing agents and metal ion chelators. Results: The pink chromogen formed with the absorbance maxima at 524 nm, AND shifted to 560 nm in alkaline pH. The absorbance was expressed as TBA-adduct in MDA units. The TBA-adduct decreased in the presence of reducing agents and metal ion chelators. Antioxidant enzymes and hydroxyl radical scavengers did not show any effect. Conclusion: Transitional metal ions in their oxidized state showed significant damage to amino acids, hydroxyproline and histidine. The results indicate the possible role played by high-valent oxo-iron species, ferryl and perferry radicals in damaging biomolecules.