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

• Published in: The European physical journal. E, Soft matter and biological physics Vol. 30; no. 2; pp. 205 - 214
• Main Authors: Aeffner, S., Reusch, T., Weinhausen, B., Salditt, T.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-10-2009; EDP Sciences
• Subjects: Biological and Medical Physics; Biological and medical sciences; Biophysics; Chemistry; Cholesterol - chemistry; Colloidal state and disperse state; Complex Fluids and Microfluidics; Complex Systems; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General and physical chemistry; Humidity; Membrane Fusion; Membrane physicochemistry; Membranes; Molecular biophysics; Nanotechnology; Neutron Diffraction - methods; Phosphatidylcholines - chemistry; Phosphatidylethanolamines - chemistry; Phospholipids - chemistry; Physics; Physics and Astronomy; Polymer Sciences; Regular Article; Soft and Granular Matter; Surfaces and Interfaces; Synchrotrons; Thin Films; X-Ray Diffraction - methods; 87.64.Bx Electron, neutron and X-ray diffraction and scattering; 87.16.D- Membranes, bilayers and vesicles; 87.15.Zg Phase transitions; 87.16.dt Structure, static correlations, domains and rafts; Membrane fusion; High content; Hydration; Report; Phase diagram; Sample; Phospholipid; Laboratory scale; Lipids; X ray; Concentration; Bilayer; Cholesterol; Binary mixture; Synchrotrons; Humidity; Membrane; X ray scattering; Mesophase; Behavior; Electron density; Structure
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/i2009-10466-x

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.