DNA-induced distamycin A fluorescence.

The fluorescent properties of the antibiotic distamycin A were investigated in a range of materials including Trypanosoma cruzi epimastigotes, chicken erythrocytes, calf thymus DNA and synthetic polynucleotides using both microscopic and spectroscopic techniques. A bright blue-white fluorescence was observed from kinetoplast DNA and chromatin after treatment with distamycin A under ultraviolet (365 nm) excitation. Considerable enhancement of distamycin A fluorescence (emission peak at 455 nm under 320-340 nm excitation) was found in the presence of DNA and poly(dA-dT).poly(dA-dT). We discuss a possible explanation for this unexpected fluorescent emission, as well as its implications for microscopic and fluorimetric studies.