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DNA and cationic surfactant complexes at hydrophilic surfaces. An ellipsometry and surface force study
Marité Cárdenas1, José Campos-Terán, Tommy Nylander
1Center for Chemistry and Chemical Engineering, Physical Chemistry 1, University of Lund, PO Box 124, SE-221 00, Sweden. marite.cardenas@fkem1.lu.se
Langmuir : the ACS Journal of Surfaces and Colloids
|September 24, 2004
Summary
DNA and cationic surfactant complexes adsorb to silica surfaces, forming layers that change thickness with coverage. Repulsive forces between these layers depend on time and experimental conditions.
Area of Science:
- Surface Chemistry
- Materials Science
- Biophysics
Background:
- Understanding interfacial phenomena is crucial for applications involving DNA and surfactants.
- Cationic surfactants and DNA interactions can lead to complex adsorption behaviors at interfaces.
Purpose of the Study:
- To investigate the adsorption of DNA and cationic surfactant complexes at the silica-aqueous interface.
- To characterize the forces between adsorbed DNA-surfactant complexes at the mica-aqueous interface.
Main Methods:
- Ellipsometry was used to study adsorption at the silica-aqueous interface.
- Interferometric surface force apparatus determined interactions at the mica-aqueous interface.
Main Results:
- Adsorption occurred with excess cationic surfactant, not on negatively charged surfaces.
- Adsorption reached steady state over hours, with layer thickness varying with surface coverage.
- Long-range repulsive forces, attributed to electrostatic and steric effects, were observed between complexes.
Conclusions:
- The adsorption of DNA-cationic surfactant complexes is dependent on surface charge and surfactant concentration.
- Adsorbed layers exhibit complex thickness changes and generate repulsive forces influenced by experimental history.