Oligonucleotides Incorporating Palladacyclic Nucleobase Surrogates

Area of Science:

• Supramolecular Chemistry
• Nucleic Acid Chemistry
• Organometallic Chemistry

Background:

• Oligonucleotides are crucial for molecular biology and nanotechnology.
• Incorporating non-natural nucleobases can expand DNA's functionality.
• Palladacyclic complexes offer unique electronic and structural properties.

Purpose of the Study:

• To synthesize and characterize an oligonucleotide containing a palladacyclic nucleobase.
• To investigate the hybridization properties of this modified oligonucleotide with natural DNA.
• To explore the stability and nature of the resulting DNA duplexes.

Main Methods:

• Ligand-directed metalation of a phenylpyridine moiety to synthesize the palladacyclic nucleobase.
• Hybridization of the modified oligonucleotide with complementary natural oligonucleotides.
• Characterization of duplexes using melting temperature (Tm) analysis and circular dichroism (CD) spectroscopy.
• UV-Vis absorption spectroscopy to monitor base pairing interactions.

Main Results:

• Successful synthesis of an oligonucleotide with a palladacyclic nucleobase.
• Formation of stable, B-type conformation DNA duplexes with comparable melting temperatures to unmodified duplexes with a single mismatch.
• Evidence of a stable palladium(II)-mediated base pair when cytosine, guanine, or thymine is opposite the palladacyclic residue.
• High absorptivity and ellipticity in palladated duplexes persisted even at 90°C, indicating resistance to dissociation.

Conclusions:

• Palladacyclic nucleobases can be incorporated into oligonucleotides.
• Palladium(II)-mediated base pairs form stable structures within DNA duplexes.
• These novel base pairs do not dissociate at high temperatures, suggesting robust molecular interactions.