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A liquid crystalline phase in spermidine-condensed DNA
J L Sikorav1, J Pelta, F Livolant
1Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes de Saclay, CEA, France.
Biophysical Journal
|October 1, 1994
Summary
Short DNA fragments condense into a cholesteric liquid crystal phase when treated with spermidine (a polyamine). This DNA ordering, driven by attractive interactions, is relevant for in vitro studies of DNA functional properties.
Area of Science:
- Biophysics
- Polymer Science
- Materials Science
Background:
- Polyamines like spermidine are crucial for DNA condensation in biological systems and are widely used in vitro.
- Understanding DNA phase behavior is essential for studying its functional properties and interactions.
Purpose of the Study:
- To investigate the phase behavior of short DNA fragments condensed by spermidine.
- To characterize the structure of the condensed DNA phase and its equilibrium with the supernatant.
Main Methods:
- Precipitation of short DNA fragments using varying concentrations of salt and spermidine.
- Observation and characterization of the resulting DNA condensed phase.
Main Results:
- Short DNA fragments precipitate into a pellet from a dilute isotropic supernatant under specific salt and spermidine concentrations.
- The DNA-condensed phase forms a cholesteric liquid crystal in equilibrium with a more concentrated phase.
- The observed liquid crystalline ordering is attributed to attractive interactions, differing from classical liquid crystalline DNA.
Conclusions:
- Spermidine-condensed DNA forms a cholesteric liquid crystalline phase, relevant for understanding DNA behavior in vitro.
- The findings align with Flory's theory for the ordering of rigid polymers with attractive interactions.
- The liquid crystalline state of spermidine-condensed DNA has implications for in vitro studies of DNA functional properties.