Equilibrium Dynamics of Spermine-induced Plasmid DNA Condensation Revealed by Fluorescence Lifetime Correlation Spectroscopy
Jana Humpolickova 1, Ales Benda 1, Jan Sykora 1, Radek Machan 1, Teresa Kral 1, Barbara Gasinska 1, Joerg Enderlein 2 and Martin Hof 1*
1 J. Heyrovsky Institute of Physical Chemistry
2 Physikalische und Theoretische Chemie, Eberhard Karls Universität Tubingen
* To whom correspondence should be addressed. E-mail: hof{at}jh-inst.cas.cz.
Submitted on September 19, 2007
Revised on October 10, 2007
Accepted on 18 October 2007
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Abstract |
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The spermine-induced DNA condensation is a first order phase transition. Here, we apply a novel technique fluorescence lifetime correlation spectroscopy to analyze this transition in a greater detail. We show that the method allows for the observation of the condensed and uncondensed molecules simultaneously based solely on different fluorescence lifetimes of the intercalating fluorophore PicoGreen® in the folded und unfolded domains of DNA. The auto- and crosscorrelation functions reveal that a small fraction of the DNA molecules is involved in the dynamic intramolecular equilibrium. Careful inspection of the crosscorrelation curves suggests that folding occurs gradually within milliseconds.
Key Words:
DNA condensation, Equilibrium Dynamics, Fluorescence correlation spectroscopy, Fluorescence lifetime correlation spectroscopy
