DNA breakage by L-DOPA and Cu(II): breakage by melanin and bacteriophage inactivation.

We have previously shown that L-DOPA in the presence of Cu(II) caused DNA cleavage through the generation of reactive oxygen species such as the hydroxyl radical. Since L-DOPA is the precursor for the synthesis of melanin, we have studied the action of melanin on DNA in a similar reaction. In this paper, we show that melanin in the presence of Cu(II) also causes DNA strand breakage. However, the rate of such strand breakage is considerably less than l-DOPA. Melanin and L-DOPA are both capable of generating superoxide anion. Furthermore, the action of L-DOPA and Cu(II) on bacteriophage lambda reduces its viability. The results are discussed in relation to the putative role of L-DOPA-Cu(II) system as a source of endogenous generation of reactive oxygen species.