Carbon-centered radicals add reversibly to histidine--implications

Area of Science:

• Biochemistry
• Physical Chemistry
• Chemical Kinetics

Background:

• Hydroxyl radical scavengers are essential tools in biochemical research.
• Understanding radical reactions is crucial for various scientific disciplines.
• Histidine residues play significant roles in protein structure and function.

Purpose of the Study:

• To investigate the reversible addition of alcohol-derived carbon radicals to histidine.
• To quantify the equilibrium and rate constants for this reaction.
• To assess the implications of these findings on electrochemical measurements.

Main Methods:

• Utilized pulse radiolysis to generate carbon-centered radicals from methanol, ethanol, isopropanol, and tert-butanol.
• Employed spectrophotometric detection to monitor radical adduct formation.
• Performed kinetic and equilibrium analyses to determine reaction parameters.

Main Results:

• Carbon-centered radicals from common alcohols add reversibly to histidine.
• Equilibrium constants reached up to 3 × 10(3) M(-1).
• Rate constants were on the order of 10(9) M(-1) s(-1).

Conclusions:

• The reversible binding of alcohol radicals to histidine is a significant interaction.
• These equilibria can potentially compromise the accuracy of one-electron radical electrode potential determinations.
• Further research is needed to account for these radical-histidine interactions in electrochemical studies.