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Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes
Published on: April 4, 2025
The quadruplex-duplex structural transition of polyriboguanylic acid
Ana G Petrovic1, Prasad L Polavarapu
1Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA.
The Journal of Physical Chemistry. B
|January 30, 2008
Summary
Polyriboguanylic acid (polyG) quadruplex structure stabilizes in 5 days near neutral pH, evidenced by spectral shifts. Acidic conditions and heat promote duplex formation, identified by unique VCD spectral markers.
Area of Science:
- Biophysical Chemistry
- Molecular Spectroscopy
- Nucleic Acid Structure
Background:
- Polyriboguanylic acid (polyG) can adopt various structural forms, including quadruplexes and duplexes.
- Understanding these structural transitions is crucial for comprehending polyG's biological roles and potential applications.
- Vibrational spectroscopy, specifically IR absorption and VCD, offers sensitive probes of molecular structure.
Purpose of the Study:
- To investigate the structural modifications of polyG under varying conditions of time, temperature, and pH.
- To correlate changes in IR and VCD spectral features with specific structural transformations of polyG.
- To identify spectral markers indicative of polyG's quadruplex and duplex forms.
Main Methods:
- Time-resolved vibrational infrared (IR) absorption spectroscopy.
- Time-resolved vibrational circular dichroism (VCD) spectroscopy.
- Comparison of experimental VCD spectra with quantum theoretical calculations.
Main Results:
- At pH 6.4, polyG stabilizes into a quadruplex structure within 5 days, characterized by a downshift in the carbonyl absorption band and a specific VCD couplet.
- In acidic conditions (pH 3.1), polyG forms a duplex structure within 5 days, marked by an additional positive VCD couplet at 1589 cm⁻¹.
- Heating polyG at pH 6.4 induces duplex formation, a transition not observed at room temperature over time. In acidic media, heating accelerates duplex formation.
Conclusions:
- The quadruplex form of polyG is characterized by a single positive VCD couplet.
- The duplex form of polyG is identified by an additional positive VCD couplet at a lower frequency.
- IR and VCD spectroscopy are powerful tools for elucidating polyG structural dynamics and identifying distinct structural forms.
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