Spontaneous formation of liquid crystalline phases and phase transitions in highly concentrated plasmid DNA |
| |
| Authors: | Piotr Hanczyc Katarzyna Matczyszyn Krzysztof Pawlik Joanna Olesiak Herve Leh Malcolm Buckle |
| |
| Institution: | 1. Group of Physics and Chemistry of Molecular Materials , Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology , Wroclaw, Poland;2. Department of Chemical and Biological Engineering , Chalmers University of Technology , Gothenburg, Sweden piotr.hanczyc@pwr.wroc.pl;4. Group of Physics and Chemistry of Molecular Materials , Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology , Wroclaw, Poland;5. Laboratory of Molecular Biology of Microorganisms , Institute of Immunology and Experimental Therapy , Wroclaw, Poland;6. Department of Toxicology , Wroclaw Medical University , Wroclaw, Poland;7. Laboratoire de Biologie et de Pharmacologie appliquée , Ecole Normale Supérieure de Cachan , France |
| |
| Abstract: | The liquid crystalline (LC) properties of two supercoiled plasmid DNA samples, pBSK (2958 bp) and pGEM (3000 bp), have been studied using polarised light microscopy (PLM), circular dichroism (CD) and UV–Vis spectroscopy. The influence of methods of isolation on plasmid LC behaviour is described, and using PLM we have demonstrated the spontaneous formation of cholesteric fingerprint-like textures. Preliminary studies of LC phase transitions in pGEM show the irreversibility of LC phase formation, as a consequence of changes in the tertiary structure of supercoiled plasmids. Using UV–Vis spectroscopy a hyperchromic effect was observed with increasing temperature. The CD spectra clearly showed structural changes, and probably mismatching of DNA bases, during cooling. Finally, we have observed an irreversible phase transition in plasmid DNA which is very different from that previously reported in linear DNA. |
| |
| Keywords: | plasmid DNA liquid crystal cholesteric phase phase transition fingerprint-like texture supercoiling hyperchromic effect DNA isolation techniques circular dichroism |
|
|
