Interaction kinetics of selenium-containing compounds with oxidants

Area of Science:

• Biochemistry
• Chemical Kinetics
• Oxidative Stress Research

Background:

• Selenium compounds are explored as biological oxidant scavengers due to selenium's nucleophilicity and facile oxidation.
• Limited data exists on the reaction kinetics of various selenium species with biologically relevant oxidants.

Purpose of the Study:

• To quantify the reaction rate constants of selenols, selenides, and diselenides with key oxidants.
• To compare the reactivity of selenium compounds with biological molecules like amino acid side chains.

Main Methods:

• Determination of apparent second-order rate constants for selenium species reacting with hypochlorous acid (HOCl), hydrogen peroxide (H2O2), other peroxides, and singlet oxygen (1O2).
• Analysis of overall consumption data for singlet oxygen (1O2) by selenium compounds.

Main Results:

• Selenols exhibit high reactivity (>10^8 M^-1 s^-1) with HOCl and 1O2.
• Selenides and diselenides show slower reaction rates compared to selenols.
• Reactivity of selenium species with HOCl and 1O2 is comparable to or exceeds that of protein amino acid side chains (Cys, Met).

Conclusions:

• Selenium compounds, particularly selenols, are potent scavengers of biologically relevant oxidants.
• Their reactivity suggests potential for developing effective, and possibly catalytic, antioxidant therapies.
• The catalytic potential arises from the facile recycling of oxidized selenium species.