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Fluorinated olefinic peptide nucleic acid: synthesis and pairing properties with complementary DNA
Marcel Hollenstein1, Christian J Leumann
1Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
The Journal of Organic Chemistry
|April 13, 2005
Summary
Fluorinated olefinic peptide nucleic acid (F-OPA) offers a novel PNA analogue for DNA recognition. While F-OPA modifications impact DNA duplex stability, its potential for self-aggregation warrants further investigation.
Area of Science:
- Biochemistry
- Organic Chemistry
- Molecular Biology
Background:
- Peptide nucleic acids (PNA) are DNA mimics with potential therapeutic applications.
- Understanding the role of specific chemical modifications in PNA base-pairing is crucial for designing effective analogues.
- The amide moiety in PNA is critical for DNA recognition, but its precise function remains under investigation.
Purpose of the Study:
- To design and synthesize a novel fluorinated PNA analogue, F-OPA, by replacing the amide group with a fluorinated double bond.
- To investigate the impact of F-OPA modifications on DNA base-pairing properties compared to PNA and its non-fluorinated analogue OPA.
- To elucidate the role of the amide function in complementary DNA recognition through comparative studies.
Main Methods:
- Synthesis of F-OPA monomer building blocks (A, T, G) using MMTr/Acyl protecting groups.
- Selective desymmetrization of the double bond via lactonization and regioselective Mitsunobu reaction for base introduction.
- Solid-phase synthesis of PNA oligomers containing F-OPA modifications (decamers, pentadecamers).
- Assessment of hybridization properties using UV melting curves and CD spectroscopy.
Main Results:
- Single (Z)-F-OPA modifications showed position-dependent effects on DNA duplex stability (T(m) ranging from +2.4 to -8.1 °C/modification).
- Fully modified F-OPA oligomers formed parallel DNA duplexes with reduced stability compared to PNA or OPA.
- An asymmetric F-OPA pentadecamer formed a stable self-complex, suggesting a propensity for self-aggregation.
Conclusions:
- The F-OPA system represents a PNA analogue with altered DNA binding characteristics.
- The fluorinated double bond influences base-pairing stability, with effects varying based on modification site.
- Reduced DNA affinity of F-OPA may stem from an increased tendency for self-aggregation, necessitating further structural studies.