Osmotically induced reversible transitions in lipid-DNA mesophases

Dganit Danino*, Ellina Kesselman, Gadiel Saper, Horia I. Petrache, Daniel Harries

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


We follow the effect of osmotic pressure on isoelectric complexes that self-assemble from mixtures of DNA and mixed neutral and cationic lipids. Using small angle x-ray diffraction and freeze-fracture cryo-electron microscopy, we find that lamellar complexes known to form in aqueous solutions can reversibly transition to hexagonal mesophases under high enough osmotic stress exerted by adding a neutral polymer. Using molecular spacings derived from x-ray diffraction, we estimate the reversible osmotic pressure-volume (Π-V) work needed to induce this transition. We find that the transition free energy is comparable to the work required to elastically bend lipid layers around DNA. Consistent with this, the required work is significantly lowered by an addition of hexanol, which is known to soften lipid bilayers. Our findings not only help to resolve the free-energy contributions associated with lipid-DNA complex formation, but they also demonstrate the importance that osmotic stress can have to the macromolecular phase geometry in realistic biological environments.

Original languageAmerican English
Pages (from-to)L43-L45
JournalBiophysical Journal
Issue number7
StatePublished - 2009

Bibliographical note

Funding Information:
We gratefully thank the help and support of Stephanie Tristram-Nagle, John Nagle, Adrian Parsegian, Don Rau, and the people of the Laboratory of Physical and Structural Biololgy, as well as funding from the intramural program of the National Institute of Child Health and Human Development. D.H. acknowledges partial support from the Israeli and Slovenian Ministries of Science through a joint Slovenian-Israeli research grant. D.D. acknowledges the support of the Russell Berrie Nanotechnology Institute at the Technion. The Fritz Haber research center is supported by the Minerva foundation, Munich, Germany.


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