Terbium as a fluorescent probe for DNA and chromatin

Area of Science:

• Biochemistry
• Biophysics
• Molecular Biology

Background:

• Terbium (Tb-3+) can serve as a sensitive fluorescent probe.
• Understanding the interaction between metal ions and nucleic acids is crucial for biochemical applications.

Purpose of the Study:

• To investigate the binding characteristics of terbium (Tb-3+) with DNA and chromatin.
• To determine the stoichiometry and reversibility of Tb-3+ binding.
• To explore the potential of Tb-3+ as a fluorescent probe for nucleic acids.

Main Methods:

• Fluorescence spectroscopy was used to measure Tb-3+ emission upon selective excitation of DNA.
• Titration experiments were performed to determine the binding stoichiometry of Tb-3+ to DNA and chromatin.
• Dialysis was employed to assess the reversibility of Tb-3+ binding.

Main Results:

• Terbium (Tb-3+) binds to DNA with a stoichiometry of one Tb-3+ per phosphate group.
• In chromatin, approximately 52% of phosphate groups were unavailable for Tb-3+ binding.
• Tb-3+ binding to DNA is reversible with 0.5 M NaCl and chelating agents.
• Optimal Tb-3+-DNA complex formation and quantum efficiency occur between pH 3 and 7, with a peak at pH 5.5-5.6.
• Low salt concentrations (up to 2 mM NaCl) enhance quantum efficiency.

Conclusions:

• Terbium (Tb-3+) is a suitable fluorescent probe for nucleic acids due to its specific binding and reversible nature.
• The binding properties of Tb-3+ can be modulated by factors such as pH and salt concentration.
• The findings suggest potential biochemical applications for Tb-3+ in studying DNA and chromatin structure and interactions.