The differential effects produced by daunomycin and adriamycin on RNA, polynucleotides, single stranded, supercoiled DNA, and nucleosomes.

Terbium, a sensitive probe whose fluorescence is strongly enhanced when bound to unpaired guanine and xanthine bases, has been employed to study the effects of adriamycin and daunomycin on a variety of nucleotide substrates. After treatment with either drug at concentrations of less than or equal to 1:500, the fluorescence of the probe was substantially abrogated. Daunomycin, however, produced a markedly greater effect than adriamycin with rRNA, linear calf thymus DNA, and polyriboguanylic acid. The difference between the drugs was experimentally significant, suggesting that changing the C9 side group from a methyl (daunomycin) to an alcohol (adriamycin) may result in a changed base sequence specificity. The distinction was also evident when changes in electrophoretic mobility of supercoiled and nucleosomal DNA was monitored, but only at much higher (1:25) drug:DNA ratios.