title: Phase diagrams of DNA-photosensitive surfactant complexes: effect of ionic strength and surfactant structure.
abstract: Realization of all-optically controlled and efficient DNA compaction is the major motivation in the study of interactions between DNA and photosensitive surfactants. In this article, using recently published approach of phase diagram construction [Y. Zakrevskyy, P. Cywinski, M. Cywinska, J. Paasche, N. Lomadze, O. Reich, H.-G. Löhmannsroben, and S. Santer, J. Chem. Phys. 140, 044907 (2014)], a strategy for substantial reduction of compaction agent concentration and simultaneous maintaining the light-induced decompaction efficiency is proposed. The role of ionic strength (NaCl concentration), as a very important environmental parameter, and surfactant structure (spacer length) on the changes of positions of phase transitions is investigated. Increase of ionic strength leads to increase of the surfactant concentration needed to compact DNA molecule. However, elongation of the spacer results to substantial reduction of this concentration. DNA compaction by surfactants with longer tails starts to take place in diluted solutions at charge ratios Z < 1 and is driven by azobenzene-aggregation compaction mechanism, which is responsible for efficient decompaction. Comparison of phase diagrams for different DNA-photosensitive surfactant systems allowed explanation and proposal of a strategy to overcome previously reported limitations of the light-induced decompaction for complexes with increasing surfactant hydrophobicity.
authors.affiliation: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Zakrevskyy
authors.affiliation: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors.forename: Evgenii
authors.initials: E
authors.lastname: Titov
authors.affiliation: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors.forename: Nino
authors.initials: N
authors.lastname: Lomadze
authors.affiliation: Experimental Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Santer
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008027:Light; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D013501:Surface-Active Agents; D004247:DNA; C009850:azobenzene