Nucleic acid secondary structures containing the double-headed nucleoside 5'(S)-C-(2-(thymin-1-yl)ethyl)thymidine

Area of Science:

• Synthetic chemistry
• Oligonucleotide chemistry
• Structural biology

Background:

• Oligodeoxynucleotides are key components in various biological processes and therapeutic applications.
• Modifying nucleosides can alter DNA structure and function.
• Previous studies explored double-headed nucleosides with methylene linkers.

Purpose of the Study:

• To synthesize and characterize oligodeoxynucleotides containing a novel double-headed nucleoside with an ethylene linker.
• To investigate the impact of this modified nucleoside on DNA secondary structures, including duplexes, bulged duplexes, three-way junctions, and DNA zippers.
• To evaluate the thermal stability and base-pairing interactions of these modified DNA structures.

Main Methods:

• Standard solid-phase synthesis of oligodeoxynucleotides.
• Stereoselective synthesis of the double-headed nucleoside building block from thymidine.
• Mitsunobu reaction for alkylating thymine.
• Thermal denaturation studies (Tm analysis) of DNA complexes.
• Analysis of DNA zipper motifs to assess base-stacking interactions.

Main Results:

• The double-headed nucleoside was successfully incorporated into oligodeoxynucleotides.
• Incorporation into duplexes and bulged duplexes resulted in a uniform, small thermal penalty, comparable to previous analogs.
• Minimal effects on thermal stability were observed in DNA or RNA three-way junctions.
• Extending the linker to ethylene reduced minor groove base-base stacking interactions in DNA zippers compared to methylene linkers.

Conclusions:

• The novel double-headed nucleoside with an ethylene linker is well-tolerated in various DNA secondary structures.
• The ethylene linker significantly alters base-stacking interactions in DNA zipper motifs.
• These findings contribute to the understanding of structure-stability relationships in modified oligonucleotides.