Structural investigations of DNA-polycation complexes

J. Derouchey, R. R. Netz, J. O. Rädler

Research output: Contribution to journalArticlepeer-review

108 Scopus citations


The internal structure of DNA-polycation complexes is investigated by synchrotron small-angle X-ray scattering (SAXS). Hexagonal packing of DNA is observed for DNA complexed with poly-L-lysine (PL), poly-L-arginine (PA), spermine (Sp), and linear and branched polyethyleneimine (lPEI and bPEI, respectively). Variations in the internal spacings and degree of long-range ordering are dependent on both polycation type and concentration of added salt. With increasing concentration of monovalent salt, a discontinuous phase transition is observed from compact to loose bundles and finally to an isotropic network phase. This salt-induced melting transition was found to be universal for all polyplexes studied and is in quantitative agreement with a simple free energy model based solely on electrostatic and entropic contributions. Using the osmotic stress method, bulk modulus (K) is measured for PL-DNA and PA-DNA polyplexes at various salt concentrations. With increasing osmotic force, we show that the salt-induced melting transition is shifted and compression in the loose bundle regime is in qualitative agreement with our model.

Original languageEnglish
Pages (from-to)17-28
Number of pages12
JournalEuropean Physical Journal E
Issue number1
StatePublished - Jan 2005

ASJC Scopus subject areas

  • Biotechnology
  • Biophysics
  • Chemistry (all)
  • Materials Science (all)
  • Surfaces and Interfaces


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