[Fluorescence study of energetics in nucleotide-actinomycin complexes]

Variety of different compounds use for delivery of antibiotics to the tumor cells. In this work, using a highly sensitive fluorescence analysis, we have studied complexes of fluorescent analog of the natural heterocyclic antibiotic actinomycin D (7-aminoactinomycin D) with potential carriers: purine bases and fragmented DNA. The antibiotic is not only adsorbed on the surface ofpurine clusters, but also is embedded in them. The antibiotic is especially well integrated into the unwound DNA regions. Embedding is accompanied by a long-wavelength shift in the excitation spectrum. The magnitude of the shift was used for calculation of the interaction energy. In the case of AMD with guanine, caffeine and adenine, the value of energy was about of 7 kcal/mol and in the case of fragmented DNA it was only a bit higher: 7.7 kcal/mol. It can be assumed that guanine, adenine, caffeine, and the fragmented DNA could apply as carriers of antibiotic.