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Analyzing Telomeric Protein-DNA Interactions Using Single-Molecule Magnetic Tweezers
Published on: August 30, 2024
Concentration-dependent structural transitions of human telomeric DNA sequences
Rashid M Abu-Ghazalah1, Steve Rutledge, Lewis W Y Lau
1Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada.
Biochemistry
|August 31, 2012
Summary
Oligodeoxyribonucleotides forming G-quadruplex structures can aggregate at high concentrations. Terminal bases may prevent aggregation, but high salt conditions can induce it in these G-rich sequences.
Area of Science:
- Biochemistry and Molecular Biology
- Structural Biology
- Spectroscopy
Background:
- Oligodeoxyribonucleotides (ODNs) with human telomeric repeats can form G-quadruplex structures.
- G-quadruplex topology is influenced by cation species, end bases, and preparation methods.
- Previous studies characterized specific monomolecular G-quadruplexes: H-Tel, hybrid-1, and hybrid-2.
Purpose of the Study:
- Investigate the concentration dependence of G-quadruplex structures using spectroscopy.
- Examine the aggregation behavior of H-Tel, hybrid-1, and hybrid-2 ODNs.
- Understand the role of terminal bases and salt conditions in G-quadruplex aggregation.
Main Methods:
- Circular Dichroism (CD) spectroscopy to monitor structural changes.
- Raman scattering to probe vibrational modes.
- Kinetic analysis of spectral transformations at varying ODN concentrations and salt conditions.
Main Results:
- H-Tel showed a concentration-dependent CD spectral transformation at millimolar concentrations, indicative of aggregate formation with a 10-hour relaxation time.
- Dilution rapidly dissociated the H-Tel aggregates, restoring monomeric spectra.
- Hybrid-1 and hybrid-2 sequences exhibited similar aggregation transitions under high-salt (1 M) conditions, suggesting a shift from monomeric to multimolecular structures.
Conclusions:
- Monomolecular G-quadruplexes can transition to multimolecular structures at typical high-resolution spectroscopy concentrations and room temperature.
- Terminal bases in hybrid sequences appear to hinder aggregate formation.
- High salt concentrations (1 M) can overcome the stabilizing effect of terminal bases, promoting aggregation in hybrid oligonucleotides.
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