Eur. Phys. J. E (2008) 27: 379-389
https://doi.org/10.1140/epje/i2008-10400-x

Regular Article

Nano-meter-sized domain formation in lipid membranes observed by small angle neutron scattering

¹ Department of Physics, Ochanomizu University, 112-8610, Tokyo, Japan
² Department of Physics and Information Sciences, Yamaguchi University, 753-8512, Yamaguchi, Japan

^* e-mail: masui.tomomi@jaea.go.jp
^** e-mail: imai@phys.ocha.ac.jp

Received: 16 February 2008
Revised: 4 August 2008
Accepted: 23 October 2008
Published online: 2 December 2008

Abstract

Using a contrast matching technique of small angle neutron scattering (SANS), we have investigated a phase separation to liquid-disordered and liquid-ordered phases on ternary small unilamellar vesicles (SUVs) composed of deuterated-saturated, hydrogenated-unsaturated phosphatidylcholine lipids and cholesterol, where the equilibrium size of these domains is constrained to less than 10nm by the system size. Below a miscibility temperature, we observed characteristic scattering profiles with a maximum, indicating the formation of nano-meter-sized domains on the SUVs. The observed profiles can be described by a multi-domain model rather than a mono-domain model. The nano-meter-sized domain is agitated by thermal fluctuations and eventually ruptured, which may result in the multi-domain state. The kinetically trapped nano-meter-sized domains grow to a mono-domain state by decreasing temperature. Furthermore, between the miscibility and disorder-order transition temperature of saturated lipid, the integrated SANS intensity increased slightly, indicating the formation of nano-meter-sized heterogeneity prior to the domain nucleation.