Evidence for two-site binding in the terbium(iii)-nucleic acid interaction

Area of Science:

• Biochemistry
• Biophysical Chemistry
• Molecular Biology

Background:

• Terbium(III) (Tb3+) is a lanthanide ion with unique luminescent properties.
• Nucleic acids, including DNA, are fundamental biomolecules with diverse structures and functions.
• Understanding metal ion interactions with nucleic acids is crucial for various biological and technological applications.

Purpose of the Study:

• To investigate the interaction of terbium(III) (Tb3+) with synthetic and native nucleic acids.
• To elucidate the binding sites and mechanisms of Tb3+ interaction with DNA and polynucleotides.
• To characterize the influence of Tb3+ on nucleic acid structure and stability.

Main Methods:

• Fluorescence spectroscopy was employed to study Tb3+ interactions.
• Equilibrium dialysis was used to determine binding affinities.
• Melting profile analysis was conducted to assess the effect of Tb3+ on DNA thermal stability.

Main Results:

• Tb3+ fluorescence is significantly enhanced by xanthine and guanine residues in nucleic acids.
• Binding affinity of Tb3+ increases with the length of polynucleotide chains.
• Tb3+ binding destabilizes helical DNA and inhibits strand reannealing.
• Two distinct Tb3+ binding sites were identified: the phosphate moiety and nucleobase electron donors.

Conclusions:

• Tb3+ serves as a sensitive probe for detecting specific nucleobases and assessing nucleic acid conformation.
• The interaction of Tb3+ with nucleic acids provides insights into metal-ion-biomolecule interactions.
• Tb3+ binding can modulate DNA structural integrity and thermal stability.