Fluorobenzene Nucleobase Analogues for Triplex-Forming Peptide Nucleic Acids

Area of Science:

• Biochemistry
• Chemical Biology
• Molecular Biology

Background:

• 2,4-Difluorotoluene, a thymidine analogue, is a probe for studying hydrogen bonding in nucleic acid interactions.
• Peptide nucleic acids (PNAs) are DNA mimics with potential in molecular recognition.
• Triple helical structures are important in RNA recognition and regulation.

Purpose of the Study:

• To evaluate fluorinated benzene analogues as nucleobases in PNAs for RNA triple helical recognition.
• To investigate the role of fluorine substitution patterns in stabilizing Hoogsteen base triplets.
• To explore non-canonical hydrogen bonding interactions involving fluorine.

Main Methods:

• Synthesis of five fluorinated benzene nucleobase analogues.
• Incorporation of analogues into peptide nucleic acid (PNA) sequences.
• Assessment of PNA-RNA triple helix formation and stability using biophysical methods.

Main Results:

• Para and ortho fluorine substitution patterns (e.g., 2,4-difluorotoluene) selectively stabilized Hoogsteen triplets with U-A base pairs.
• Stabilization is attributed to attractive electrostatic interactions, including non-canonical F to H-N and C-H to N hydrogen bonding.
• Fluorinated nucleobases did not stabilize Hoogsteen-like triplets with G-C or A-U base pairs.

Conclusions:

• Fluorine can engage in non-canonical base pairing interactions.
• Fluorinated PNA analogues offer a strategy for selective RNA triple helix recognition.
• Findings provide insights into fluorine's role in molecular recognition and nucleic acid interactions.