peroksiradikaaleja

Peroxyl radicals are reactive species containing an oxygen–oxygen single bond attached to an organic fragment. They are typically produced in biological systems through the partial reduction of molecular oxygen, a process often mediated by transition metal catalysts or enzymatic reactions. The general structural formula of a peroxyl radical is R–O–O•, where R represents an organic group. Because of the unpaired electron on one of the oxygen atoms, peroxyl radicals are highly reactive and play a key role in oxidation reactions in both living organisms and the environment.

In biochemistry, peroxyl radicals arise mainly from autoxidation of lipids and proteins. Polyunsaturated fatty acids, when exposed to transition metals, can undergo a homolytic cleavage of a C–H bond, forming a carbon-centered radical that rapidly reacts with oxygen to produce a lipid peroxyl radical. These radicals propagate chain reactions that result in lipid peroxidation, which is implicated in cell membrane damage, aging, and various diseases such as atherosclerosis and neurodegeneration.

Antioxidants in biological systems mitigate the harmful effects of peroxyl radicals. Glutathione peroxidases, thioredoxin, and small molecules like vitamin E intercept peroxyl radicals, converting them into less reactive species. The balance between radical formation and antioxidant defense determines oxidative stress levels in cells.

Peroxyl radicals are also significant in atmospheric chemistry. They participate in the catalytic cycles that decompose pollutants and are involved in the formation of secondary organic aerosols. Their reaction kinetics can be influenced by temperature, humidity, and the presence of other radical species.

Because peroxyl radicals are central to both biological oxidative processes and atmospheric chemistry, they remain a subject of extensive research. Studies focus on their mechanisms, influence on cellular signaling, and potential as therapeutic targets or environmental markers.