DNA and cationic surfactant complexes at hydrophilic surfaces. An ellipsometry and surface force study.
The adsorption and formation of DNA and cationic surfactant complexes at the silica-aqueous interface have been studied by ellipsometry. The interaction between the DNA-surfactant complexes at the mica-aqueous interface has been determined by the interferometric surface force apparatus. Adsorption was as expected not observed on negatively charged hydrophilic surfaces for DNA and when DNA-cationic surfactant complexes were negatively charged. However, adsorption was observed when there is an excess of cationic surfactant, just below the point of phase separation. The adsorption process requires hours to reach steady state. The adsorbed layer thickness is large at low surface coverage but becomes more compact and thinner at high coverage. A long-range repulsive force was observed between adsorbed layers of DNA-cationic surfactant complexes, which was suggested to be of both electrostatic and steric origin. The forces were found to be dependent on the equilibration time and the experimental pathway.
Cárdenas
Marité
M
Center for Chemistry and Chemical Engineering, Physical Chemistry 1, University of Lund, PO Box 124, SE-221 00, Sweden. marite.cardenas@fkem1.lu.se
Campos-Terán
José
J
Nylander
Tommy
T
Lindman
Björn
B
D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry
D000538:Aluminum Silicates; D002412:Cations; D046911:Macromolecular Substances; D013501:Surface-Active Agents; D014867:Water; D004247:DNA; C011934:mica