Eur. Phys. J. E (2009) 30: 205-214
https://doi.org/10.1140/epje/i2009-10466-x

Regular Article

Membrane fusion intermediates and the effect of cholesterol: An in-house X-ray scattering study

Institut für Röntgenphysik, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany

^* e-mail: saeffne@gwdg.de
^** e-mail: tsaldit@gwdg.de

Received: 22 December 2008
Revised: 5 April 2009
Accepted: 23 April 2009
Published online: 17 June 2009

Abstract

We have developed an X-ray scattering setup which allows to study membrane fusion intermediates or other nonlamellar lipid mesophases by laboratory-scale X-ray sources alone, thus taking advantage of unrestricted beamtime compared to synchrotron sources. We report results of a study of pure lipid bilayers and phospholipid/cholesterol binary mixtures. Stalks, putative intermediate structures occurring during the membrane fusion process, can clearly be identified from reconstructed electron density maps. Phase diagrams of the lyotropic phase behavior of DOPC/cholesterol and DPhPC/cholesterol samples are presented. If cholesterol is present in moderate concentrations, it can substantially promote the formation of stalks at higher degree of hydration. In addition, a possibly new phase in DOPC/cholesterol is found at high cholesterol content in the low humidity range.