Although it is generally believed that one of the major biological functions of melanin is photoprotection, its molecular mechanism is not fully understood. Thus it can be argued that besides simple light screening, melanin exerts its photoprotective action via sequestration of heavy metal ions and scavenging of reactive free radicals. Of course, the ability of melanin to scavenge free radicals is likely to depend on their physicochemical properties: their lifetime, one-electron reduction potential, and net charge. We studied the interaction of two synthetic polymers, dopa melanin (DM) and cysteinyldopa melanin (CDM), with a series of reducing and oxidizing free radicals. Our data indicate that melanin can act as a powerful scavenger both for oxidizing and reducing radicals. [unreadable]