Modulation of oligonucleotide duplex and triplex stability via hydrophobic interactions

Area of Science:

• Biochemistry
• Medicinal Chemistry
• Molecular Biology

Background:

• Synthetic oligonucleotides are a novel class of pharmaceuticals.
• Their mechanism involves Watson-Crick or Hoogsteen base pairing with target nucleic acids.
• Cholesterol conjugation is explored to enhance oligonucleotide properties.

Purpose of the Study:

• To synthesize and evaluate cholesterol-conjugated oligonucleotides.
• To investigate the impact of cholesterol conjugation on duplex and triplex stability.
• To assess the specificity and mismatch discrimination of these modified oligonucleotides.

Main Methods:

• Synthesis of 3'-cholesterol and/or 5'-cholesterol conjugated oligonucleotides.
• Formation of tandemly addressed duplexes and clamp-shaped triplexes.
• Measurement of duplex and triplex melting temperatures (Tm) to assess stability.
• Evaluation of mismatch discrimination using various oligonucleotide constructs.

Main Results:

• Duplexes formed by tandem oligonucleotides showed increased Tm up to 13.3°C.
• Cholesterol conjugates exhibited improved mismatch discrimination compared to unmodified oligomers.
• 5',3'-bis-cholesterol oligomers formed stable triple-stranded complexes with Tm stabilization up to 30°C.
• No triplex formation was detected with mismatched targets.

Conclusions:

• Hydrophobic interactions between cholesterol moieties significantly stabilize nucleic acid complexes.
• Cholesterol conjugation enhances both the stability and specificity of synthetic oligonucleotides.
• These findings support the potential of cholesterol-conjugated oligonucleotides as therapeutic agents.