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Hybridization of peptide nucleic acid
T Ratilainen1, A Holmén, E Tuite
1Department of Physical Chemistry, Chalmers University of Technology, Gothenburg, Sweden.
Biochemistry
|September 2, 1998
Summary
Fluorescent dyes significantly impact the stability and structure of PNA/DNA and PNA/PNA duplexes, altering hybridization thermodynamics and helical sense. Dye interactions can either stabilize or destabilize these nucleic acid structures.
Area of Science:
- Biophysical Chemistry
- Nucleic Acid Chemistry
- Molecular Biophysics
Background:
- Understanding the thermodynamics and conformations of nucleic acid duplexes is crucial for their application.
- Peptide nucleic acid (PNA) offers unique properties compared to DNA, enabling novel hybrid structures.
- Fluorescent labeling is a common technique for studying biomolecular interactions but can potentially perturb structures.
Purpose of the Study:
- To investigate the thermodynamics and conformations of PNA/PNA, PNA/DNA, and DNA/DNA duplexes.
- To evaluate the influence of fluorescent labels (fluorescein and rhodamine) on duplex stability and structure.
- To compare different thermodynamic measurement techniques, including fluorescence energy transfer (FET), absorption hypochromicity (ABS), and isothermal titration calorimetry (ITC).
Main Methods:
- Fluorescence Energy Transfer (FET) for interchromophoric distance measurements and duplex melting.
- Absorption Hypochromicity (ABS) for studying duplex melting thermodynamics.
- Isothermal Titration Calorimetry (ITC) and Circular Dichroism (CD) for thermodynamic and structural characterization.
Main Results:
- Solution structures of duplexes were determined to be extended helices, consistent with NMR and X-ray data.
- Discrepancies in thermodynamic parameters between FET and ABS were observed, attributed to dye-induced stability changes.
- Fluorescein labeling significantly altered duplex stability: stabilization (3-4°C increase in Tm) via attractive interactions with PNA, and destabilization (-12°C decrease in Tm) in PNA/DNA duplexes due to electrostatic repulsion. Dye conjugation also reversed helicity in PNA/PNA duplexes.
Conclusions:
- Fluorescent dyes, particularly fluorescein, exert a substantial influence on the hybridization thermodynamics and structural integrity of PNA-containing duplexes.
- The observed effects are dependent on the dye's charge, linker, and the specific nucleic acid sequence (PNA/PNA vs. PNA/DNA).
- Careful consideration of dye-biomolecule interactions is essential when using labeled nucleic acids for biophysical studies.