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The folding of centromeric DNA strands into intercalated structures: a physicochemical and computational study
J Gallego1, E B Golden, D E Stanley
1Chemistry Department, University of Washington, Seattle, WA, 98195-1700, USA. jgallego@u.washington.edu
Journal of Molecular Biology
|January 15, 1999
Summary
Intercalated DNA stability arises from electrostatic interactions between protonated and neutral cytosines, alongside non-polar forces. These factors overcome entropic and solvation penalties for DNA strand association.
Area of Science:
- Biophysics
- Computational Biology
- Structural Biology
Background:
- Cytosine-rich DNA can form intercalated structures.
- Understanding the stability of these structures is crucial for DNA recognition and function.
Purpose of the Study:
- To analyze the physicochemical and computational basis of stability in intercalated DNA structures.
- To compare these findings with Watson-Crick duplexes and experimental thermodynamic data.
Main Methods:
- Physicochemical analysis.
- Computational modeling using Poisson-Boltzmann for electrostatics and van der Waals functions for non-polar components.
- Comparison with UV experimental thermodynamic data.
Main Results:
- Intercalated DNA is stabilized by favorable electrostatic interactions between protonated (C+) and neutral cytosines.
- Non-polar forces, including hydrophobic effects and van der Waals contacts, also contribute significantly.
- Cytosine protonation drives tetrameric structure formation, but solvent effects attenuate electrostatic interactions in stacked C.C+ pairs.
Conclusions:
- The stability of intercalated DNA is a balance of electrostatic and non-polar forces, overcoming entropic and solvation energy costs.
- Solvation free energy is less favorable for protonated DNA due to charge neutralization.
- Findings may inform understanding of other protonated nucleic acid structures like triplexes.