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

Abstract

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+.

Conformational transitions of poly(dA-dC).poly(dG-dT) induced by high salt or in ethanolic solution

“…Also, a given cation may have very different effects on different systems. It was shown (28) that Th ions are very efficient at 10 5 M to induce the Z form in poly(dG-dC)&poly(dG-dC), in poly(dA-dC).poly(dG-dT)they cause a decrease of the CD spectrum similar to that in fig. 3,a.…”

Terbium(III)‐induced conformational transition in poly(dG‐dC) fluorescence and circular dichroic studies

“…Haertle et al [15] have shown recently that in low salt aqueous medium (pH 6) Tb(III) induces the B-+Z transition in poly(dG-dC), with enhancement of the fluorescence intensity. However, no further analysis of the left-handed CD pattern in the presence of Tb(III) has been attempted here.…”

“…The increase in the induced fluorescence intensity of Tb(II1) in the later case, is dramatic, and an order of magnitude higher than that of the Tb(III)-right handed DNA complex. By analyzing the CD spectral change induced by Tb(lII) on poly(dG-dC) in aqueous medium [15] i.e. from the ratio of the positive to negative ellipticities, it appears that Tb(III)-poly(dG-dC) may not be in the exact lefthanded DNA configuration, but rather is represented by some intermediate form.…”

DNA Liquid-Crystalline Dispersion Particles as a Platform for Creation of “RIGID” Spatial Structures

“…Because each phosphate group of the DNA molecules, carrying one "effective" negative charge, is neutralized by Gd 3+ ion [20], which carries three positive charges, this means that the altered surface charge distribution makes an additional contribution to the chiral interaction between adjacent (ds DNA-Gd 3+ ) complexes in the particles [21,22]. In this case one can expect that the pitch of the spatial twist of cholesteric structure formed by the ds DNA is changed as a result of interaction of Gd 3+ ions with these molecules [17].…”