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Updated: Jul 24, 2025
09:06
Preparation of DNA-crosslinked Polyacrylamide Hydrogels
Published on: August 27, 2014
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Ion-induced changes in DNA gels
Ferenc Horkay1, Peter J Basser1, Erik Geissler2
1Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 13 South Drive, Bethesda, MD 20892, USA. horkayf@mail.nih.gov.
Soft Matter
|July 10, 2023
Summary
Small angle neutron scattering reveals how DNA gel structure changes with ion concentration and pH. Increased calcium chloride or lower pH leads to DNA gel phase separation.
Area of Science:
- Biophysics
- Materials Science
- Polymer Science
Background:
- DNA gels are complex networks with properties influenced by their ionic environment.
- Understanding DNA gel behavior is crucial for applications in biotechnology and biomaterials.
Purpose of the Study:
- To investigate the structural changes in DNA gels under varying ionic conditions using small angle neutron scattering (SANS).
- To correlate changes in ion concentration and pH with DNA gel network properties and phase behavior.
Main Methods:
- Small angle neutron scattering (SANS) measurements on DNA gels.
- Variation of monovalent and divalent counter-ion concentrations and pH.
- Anomalous small angle X-ray scattering (ASAXS) for ion cloud analysis.
- Osmotic pressure measurements.
Main Results:
- SANS data fitted with a two-term equation accounting for fluctuations and static inhomogeneities.
- Low q-range SANS indicates large cluster formation.
- Intermediate q-range scattering suggests rod-like structures with increasing CaCl2 concentration.
- High q-region scattering reflects local chain geometry.
- NaCl screening increases SANS intensity and mesh size; CaCl2 or decreased pH leads to phase separation.
- SANS-derived I(0) agrees well with osmotic pressure measurements.
- ASAXS shows weak influence of divalent ions on monovalent ion clouds, but tight following of polymer chains by divalent counter-ions.
Conclusions:
- Ionic strength and pH significantly alter DNA gel structure, mesh size, and can induce phase separation.
- SANS is a powerful tool for characterizing DNA gel networks and their response to environmental changes.
- Counter-ion behavior is distinct for monovalent and divalent ions, impacting DNA gel properties.
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