REACTION OF NITRIC-OXIDE WITH IRON BLEOMYCIN BOUND TO DNA - PROPERTIES OF THE NITROSYL ADDUCT AND ITS REACTION WITH O-2

During the ESR spectroscopic titration of nitrosyl-iron bleomycin, ON- Fe(II)Blm, with DNA, its metal domain undergoes a change in environmen t as the DNA base pair to drug ratio increases to 50 to 1. The N-15-O stretching frequency of ON-Fe(II) Blm occurs at 1589 cm(-1) similar to that for nitrosyl hemoglobin and myoglobin. Upon addition of DNA (3 b ase pairs per drug molecule), this vibration is substantially broadene d. Injection of O-2 into a solution of ON-Fe(II) BlmDNA converts the E SR signal of the nitrosyl species to low spin Fe(III)BlmDNA. NO is lar gely oxidized to NO2-. The combination of these products suggests that the initial reaction of ON-Fe(II)Blm with O-2 generates Fe(III)Blm an d peroxynitrite, O2NO-. If peroxynitrite is formed in the reaction, it does not cause detectable DNA damage. The structural integrity of a s upercoiled DNA plasmid, pBR322, is not compromised and no base propena ls are produced during this reaction.