[Synthesis of spin-labeled rubomycin and a study of its interaction with DNA]

Hydrochloride of 14-(I-oxyl-2,2,6,6-tetramethylpiperidyl-4)-acetoxyrubomycin (spin-labeled rubomycin or SL-rubomycin) was prepared by interaction of hydrochloride of 14-bromrubomycin with potassium salt of I-oxyl-2,2,6,6-tetramethylpiperidyl-4-acetic acid. Its interaction with DNA and synthetic poly A and poly U polyribonucleotides was studied. The character of the EPR spectra was indicative of DNA binding with SL-rubomycin and forming a system with a high level of regularity similar to that of liquid crystals. The results of the study of the EPR spectra correlated with the model of rubomycin intercalation between the pairs of DNA bases and were indicative of water surrounding of the nitroxyl group of SL-rubomycin bound with DNA.