Eur. Phys. J. E 4, 115-120

Structure factor of a lamellar smectic phase with inclusions

P. Sens¹ and M.S. Turner².

¹  Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg Cedex, France
²  Rockefeller University, New York, NY 10021 USA and Department of Physics, Warwick University, Coventry, CV4 7AL, UK

sens@ics.u-strasbg.fr

(Received 10 March 2000 and Received in final form 30 August 2000)

Abstract
Motivated by numerous X-ray scattering studies of lamellar phases with membrane proteins, amphiphilic peptides, polymers, or other inclusions, we have determined the modifications of the classical Caillé law for a smectic phase as a function of the nature and concentration of inclusions added to it. Besides a fundamental interest on the behavior of fluctuating systems with inclusions, a precise characterization of the action of a given protein on a lipid membrane (anchoring, swelling, stiffening ...) is of direct biological interest and could be probed by way of X-ray measurements. As a first step we consider three different couplings involving local pinching (or swelling), stiffening or curvature of the membrane. In the first two cases we predict that independent inclusions induce a simple renormalization of the bending and compression moduli of the smectic phase. The X-ray experiments may also be used to probe correlations between inclusions. Finally we show that asymmetric coupling (such as a local curvature of the membrane) results in a modification of the usual Caillé law.

PACS
87.22.Bt - Membrane and subcellular physics and structure.
82.65.Dp - Thermodynamics of surfaces and interfaces.
82.70.-y - Disperse systems.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001