Sequence specific hybridization properties of methylphosphonate oligodeoxynucleotides.

Area of Science:

• Oligonucleotide Chemistry
• Biophysical Chemistry
• Molecular Biology

Background:

• Methylphosphonate oligodeoxynucleotides (MPOs) are modified nucleic acids with potential therapeutic applications.
• Ensuring isomeric purity of the methylphosphonate (MP) linkage is crucial for predictable structure-property relationships.

Purpose of the Study:

• To synthesize and characterize MPOs containing isomerically pure Rp-methylphosphonates.
• To investigate the duplex stability and thermodynamic properties of these MPOs.
• To explore the structural impact of Rp-MP linkages on oligonucleotide conformation.

Main Methods:

• Synthesis of dinucleoside methylphosphonates (DMPs) and subsequent block coupling to form 20-mer MPO duplexes.
• Melting temperature (Tm) analysis to assess duplex stability.
• Concentration-dependent Tm studies to determine thermodynamic parameters.
• Circular Dichroism (CD) spectroscopy to analyze secondary structure.

Main Results:

• Successful synthesis of MPOs with isomerically pure Rp-MP linkages.
• Duplexes exhibited melting temperatures comparable to phosphorodiester counterparts.
• Duplex stability was influenced by adjacent nucleosides.
• First determination of thermodynamic parameters for the duplex-coil transition of isomerically pure MPOs.
• CD spectra indicated structural changes associated with helix formation.

Conclusions:

• Isomerically pure Rp-MP linkages can form stable oligonucleotide duplexes with properties similar to natural DNA.
• The sequence context significantly affects the stability of MPO duplexes.
• This work provides valuable thermodynamic and structural insights into Rp-MP modified oligonucleotides.