Is Tb3+ fluorescence enhancement only due to binding to single stranded polynucleotides

Enhancement of Tb3+ fluorescence upon binding to double-stranded ribo- and deoxyribo-duplexes was investigated. It was observed that certain double stranded ribopolynucleotides completely quenched the Tb3+ fluorescence and others did not. It is concluded that the nature of the base in the duplex is critical for this enhancement. - Polydeoxyduplexes also showed enhancement of Tb3+ fluorescence, but much higher terbium concentrations were necessary to obtain similar fluorescence signals, indicative of unspecific effects. CD spectra evidence considerable conformational changes of these duplexes, in particular poly(dG-C) . poly(dG-C( which assumes the Z-form in 0.1 nM Tb3+.