DECREASE OF MELTING TEMPERATURE AND SINGLE STRAND SCISSION OF DNA BY BLEOMYCIN IN THE PRESENCE OF 2-MERCAPT0ETHAN0L

Abstract

Decrease of melting temperature (Tm) of Escherichia coli 15T^- DNA, with little breakage of the DNA strand, was observed in the presence of bleomycin A₂ and 2-mercaptoethanol. DNA digested more drastically with pancreatic deoxyribonuclease (E. C. 3.1.4.5) revealed no shift of Tm. When the DNA, treated with bleomycin and 2-mercaptoethanol, was dialyzed after heat denaturation, marked strand scission occurred. Tm of poly (dG)•poly (dC) decreased by 9°C with a change of transition width at 40μg/ml of bleomycin, although that of poly d(AT)•poly d(TA) showed no change. Single strand scission of synthetic deoxyribopolymers was observed to occur slightly in the presence of bleomycin and markedly when dialyzed after the incubation. Strand scission without dialysis was produced more significantly on poly (dG).poly (dC) than poly d(AT)•poly d(TA) in the presence of bleomycin.