Time-resolved fluorescence studies of the interaction of the Eu3+ complexes of tetracycline analogues with DNA

The interaction of the Eu3+ complexes of tetracycline analogues with DNA has been examined by using UV-visible absorption and fluorescence spectra. Among the tetracycline series, the europium fluorescence sensitized by tetracycline (TC) and oxytetracycline (OTC) were enhanced by DNA more than those of other antibiotics in the series. Therefore, Eu3+-TC-DNA and Eu3+-OTC-DNA systems were investigated by time-resolved fluorescence. The Eu3+-OTC complex is a more sensitive fluorescence probe for selective determination of DNA than the Eu3+-TC complex. Detection limits (signal/ noise = 2) for DNA are 2.4 and 5.0 ng ml−1 for the OTC and TC systems, respectively.