Eur. Phys. J. E (2007) 23: 431-437
https://doi.org/10.1140/epje/i2007-10203-7

Regular Article

Active membranes studied by X-ray scattering

¹ Institut für Röntgenphysik, Friedrich-Hund-Platz 1, 37073, Göttingen, Germany
² Laboratoire Physico Chimie, Unité Mixte de Recherche 168 Centre National de la Recherche Scientifique/Institut Curie, 75231, Paris Cedex 05, France

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

Received: 26 February 2007
Accepted: 5 July 2007
Published online: 22 August 2007

Abstract

In view of recent theories of “active” membranes, we have studied multilamellar phospholipid membrane stacks with reconstituted transmembrane protein bacteriorhodopsin (BR) under different illumination conditions by X-ray scattering. The light-active protein is considered as an active constituent which drives the system out of equilibrium and is predicted to change the collective fluctuation properties of the membranes. Using X-ray reflectivity, X-ray non-specular (diffuse) scattering, and grazing incidence scattering, we find no detectable change in the scattering curves when changing the illumination condition. In particular the intermembrane spacing d remains constant, after eliminating hydration-related artifacts by design of a suitable sample environment. The absence of any observable non-equilibrium effects in the experimental window is discussed in view of the relevant parameters and recent theories.