Eur. Phys. J. E (2005) 18: 447-458
https://doi.org/10.1140/epje/e2005-00046-5

Regular Articles

Detection of submicron-sized raft-like domains in membranes by small-angle neutron scattering

¹ National Research Council, Canadian Neutron Beam Centre, Chalk River Laboratories, Building 459, Station 18, Chalk River, ON, K0J 1J0, Canada
² NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Stop 8562, Bldg. 235/Room E151, Gaithersburg, MD, 20899-8562, USA
³ Department of Physics, St. Francis Xavier University, Antigonish, NS, B2G 2W5, Canada
⁴ Department of Physics and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853-2501, USA
⁵ Atomic Energy of Canada Ltd., Chalk River Laboratories, Chalk River, ON, K0J 1J0, Canada
⁶ Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, L8N 3Z5, Canada
⁷ Guelph-Waterloo Physics Institute and Biophysics Departmental Group, University of Guelph, Guelph, ON, N1G 2W1, Canada

^* e-mail: Jeremy.Pencer@nrc.gc.ca
^** e-mail: John.Katsaras@nrc.gc.ca

Received: 22 March 2005
Published online: 15 November 2005

Abstract

Using coarse grained models of heterogeneous vesicles we demonstrate the potential for small-angle neutron scattering (SANS) to detect and distinguish between two different categories of lateral segregation: 1) unilamellar vesicles (ULV) containing a single domain and 2) the formation of several small domains or “clusters” (~10 nm in radius) on a ULV. Exploiting the unique sensitivity of neutron scattering to differences between hydrogen and deuterium, we show that the liquid ordered (lo) DPPC-rich phase can be selectively labeled using chain deuterated dipalymitoyl phosphatidylcholine (dDPPC), which greatly facilitates the use of SANS to detect membrane domains. SANS experiments are then performed in order to detect and characterize, on nanometer length scales, lateral heterogeneities, or so-called “rafts”, in ~30 nm radius low polydispersity ULV made up of ternary mixtures of phospholipids and cholesterol. For 1:1:1 DOPC:DPPC:cholesterol (DDC) ULV we find evidence for the formation of lateral heterogeneities on cooling below 30 °C. These heterogeneities do not appear when DOPC is replaced by SOPC. Fits to the experimental data using coarse grained models show that, at room temperature, DDC ULV each exhibit approximately 30 domains with average radii of ~10 nm.