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 with L-DOPA. Melanin and L-DOPA an 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. (C) 1998 Elsevier Science B.V.