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Adsorption of divalent cations on DNA
Isabelle Morfin1, Ferenc Horkay, Peter J Basser
1Laboratoire de Spectrométrie Physique, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5588, Université Joseph Fourier de Grenoble, St. Martin d'Hères, France.
Biophysical Journal
|September 30, 2004
Summary
Divalent ions like strontium and calcium influence DNA structure in solutions. Their concentration affects the DNA
Area of Science:
- Biophysics
- Polymer Physics
- Solution Chemistry
Background:
- High-molecular-mass DNA solutions are fundamental in biological and material science.
- Understanding ion distribution around DNA is crucial for its structural stability and function.
- Near-physiological conditions are relevant for biological applications.
Purpose of the Study:
- To investigate the distribution of divalent ions (strontium and calcium) around DNA in semidilute solutions.
- To determine the structural response of DNA to varying divalent ion concentrations.
- To compare the effects of strontium chloride and calcium chloride on DNA counterion sheaths.
Main Methods:
- Small-angle X-ray scattering (SAXS) to probe nanoscale structures.
- Small-angle neutron scattering (SANS) for complementary structural information.
- Analysis of scattering intensity at varying scattering vector (q) magnitudes.
Main Results:
- Scattering intensity increases at low q with higher divalent ion concentration.
- DNA strands (radius ~10 Å) are surrounded by a counterion sheath (~13.8 Å).
- Sheath thickness is independent of strontium chloride concentration but increases as calcium chloride concentration decreases.
Conclusions:
- Divalent ions partially localize in a layer thinner than the Debye screening length.
- DNA counterion sheath structure is sensitive to the type and concentration of divalent cations.
- These findings provide insights into ion-DNA interactions in complex solutions.