Osmotically induced reversible transitions in lipid-DNA mesophases

TY - JOUR

T1 - Osmotically induced reversible transitions in lipid-DNA mesophases

AU - Danino, Dganit

AU - Kesselman, Ellina

AU - Saper, Gadiel

AU - Petrache, Horia I.

AU - Harries, Daniel

N1 - 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.

PY - 2009

Y1 - 2009

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=67649307081&partnerID=8YFLogxK

U2 - 10.1016/j.bpj.2008.12.3887

DO - 10.1016/j.bpj.2008.12.3887

M3 - 文章

C2 - 19348739

AN - SCOPUS:67649307081

SN - 0006-3495

VL - 96

SP - L43-L45

JO - Biophysical Journal

JF - Biophysical Journal

IS - 7

ER -