Stabilizing and destabilizing effects of intercalators on DNA triplexes

Area of Science:

• Molecular Biology
• Biotechnology
• Biophysics

Background:

• Oligonucleotide triplex formation is crucial for diagnostics and biotechnology.
• Intercalating ligands significantly influence triplex stability, dependent on sequence, intercalator type, and conditions.

Purpose of the Study:

• To determine the optimal number of intercalated ethidium bromide (EtBr) and acridine orange (AO) molecules for triplex stabilization.
• To investigate the concentration-dependent effects of EtBr and AO on parallel (recombinant) and antiparallel triplex stability.

Main Methods:

• Characterization of fluorescent complexes of intramolecular parallel (parARB) and antiparallel (antiATT) triplexes with EtBr and AO.
• Estimation of EtBr and AO concentrations for an average of one, two, or three intercalated molecules.
• Thermal denaturation studies and evaluation of thermodynamic parameters using a three-state model.

Main Results:

• Both EtBr and AO binding constants were determined and compared to DNA duplexes.
• Triplex stabilization by EtBr and AO was found to be concentration-dependent.
• The first two intercalated molecules stabilized triplexes, while the third molecule significantly destabilized them.

Conclusions:

• The number of intercalated molecules critically affects oligonucleotide triplex stability.
• EtBr and AO can be used to modulate triplex stability, with optimal stabilization achieved at specific binding concentrations.
• Understanding these interactions is key for developing oligonucleotide-based diagnostic and biotechnological tools.