@article{ZakrevskyyRoxlauBrezesinskietal.2014,
  author    = {Zakrevskyy, Yuriy and Roxlau, Julian and Brezesinski, Gerald and Lomadze, Nino and Santer, Svetlana A.},
  title     = {Photosensitive surfactants: Micellization and interaction with DNA},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {140},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4862678},
  pages     = {8},
  year      = {2014},
  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.},
  language  = {en}
}
@article{ZakrevskyyCywinskiCywinskaetal.2014,
  author    = {Zakrevskyy, Yuriy and Cywinski, Piotr and Cywinska, Magdalena and Paasche, Jens and Lomadze, Nino and Reich, Oliver and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Santer, Svetlana A.},
  title     = {Interaction of photosensitive surfactant with DNA and poly acrylic acid},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {140},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4862679},
  pages     = {8},
  year      = {2014},
  language  = {en}
}
@article{ZakrevskyyTitovLomadzeetal.2014,
  author    = {Zakrevskyy, Yuriy and Titov, Evgenii and Lomadze, Nino and Santer, Svetlana A.},
  title     = {Phase diagrams of DNA-photosensitive surfactant complexes: Effect of ionic strength and surfactant structure},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {141},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {16},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4899281},
  pages     = {8},
  year      = {2014},
  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. Lohmannsroben, 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. (C) 2014 AIP Publishing LLC.},
  language  = {en}
}
@article{RichterZakrevskyyEiseleetal.2014,
  author    = {Richter, Marcel and Zakrevskyy, Yuriy and Eisele, Michael and Lomadze, Nino and Santer, Svetlana A. and von Klitzing, Regine},
  title     = {Effect of pH, co-monomer content, and surfactant structure on the swelling behavior of microgel-azobenzene-containing surfactant complex},
  series = {Polymer : the international journal for the science and technology of polymers},
  volume    = {55},
  journal   = {Polymer : the international journal for the science and technology of polymers},
  number    = {25},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0032-3861},
  doi       = {10.1016/j.polymer.2014.10.027},
  pages     = {6513 -- 6518},
  year      = {2014},
  abstract  = {The contraction/swelling transition of anionic PNIPAM-co-AAA particles can be manipulated by light using interactions with cationic azobenzene-containing surfactant. In this study the influence of pH-buffers and their concentrations, the charge density (AAA content) in microgel particles as well as the spacer length of the surfactant on the complex formation between the microgel and surfactant is investigated. It is shown that the presence of pH buffer can lead to complete blocking of the interactions in such complexes and the resulting microgel contraction/swelling response. There is a clear competition between the buffer ions and the surfactant molecules interacting with microgel particles. When working in pure water solutions with fixed concentration (charge density) of microgel, the contraction/swelling of the particles is controlled only by relative concentration (charge ratio) of the surfactant and AAA groups of the microgel. Furthermore, the particle contraction is more efficient for shorter spacer length of the surfactant. The onset point of the contraction process is not affected by the surfactant hydrophobicity. This work provides new insight into the interaction between microgel particles and photo-sensitive surfactants, which offers high potential in new sensor systems. (C) 2014 Elsevier Ltd. All rights reserved.},
  language  = {en}
}