title: Photosensitive surfactants: micellization and interaction with DNA.
abstract: Recently, photosensitive surfactants have re-attracted considerable attention. It has been shown that their association with oppositely charged biologically important polyelectrolytes, such as DNA or microgels, can be efficiently manipulated simply by light exposure. In this article, we investigate the self-assembly of photosensitive surfactants as well as their interactions with DNA by calorimetric and spectroscopic methods. Critical micelle concentration (CMC), standard micellization enthalpy, entropy, and Gibbs energy were determined in different conditions (ionic strengths and temperatures) for a series of cationic surfactants with an azobenzene group in their tail. It is shown, that aggregation forces of photosensitive units play an important role in the micellization giving the major contribution to the micellization enthalpy. The onset of the aggregation can be traced from shift of the absorption peak position in the UV-visible spectrum. Titration UV-visible spectroscopy is used as an alternative, simple, and sensitive approach to estimate CMC. The titration UV-visible spectroscopy was also employed to investigate interactions (CAC: critical aggregation concentration, precipitation, and colloidal stabilization) in the DNA-surfactant complex.
authors: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors: Yuriy
authors: Y
authors: Zakrevskyy
authors: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors: Julian
authors: J
authors: Roxlau
authors: Department of Interfaces, Max Planck Institute of Colloids and Interfaces, Research Campus Potsdam-Golm, D-14476 Potsdam, Germany.
authors: Gerald
authors: G
authors: Brezesinski
authors: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors: Nino
authors: N
authors: Lomadze
authors: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors: Svetlana
authors: S
authors: Santer
mesh_terms: D000818:Animals; D001391:Azo Compounds / Q000737:chemistry; D002151:Calorimetry; D002417:Cattle; D004247:DNA / Q000737:chemistry*; D019277:Entropy; D008823:Micelles; D008956:Models, Chemical; D009994:Osmolar Concentration; D055668:Photochemical Processes; D013057:Spectrum Analysis; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D013950:Thymus Gland; D014867:Water / Q000737:chemistry
chemical_list: D001391:Azo Compounds; D008823:Micelles; D013501:Surface-Active Agents; D014867:Water; D004247:DNA; C009850:azobenzene