Laboratoire de Physique Théorique
Toulouse - UMR 5152

Artificial lipid vesicles offer a medium on which we can isolate and study phenomenons that would be much more difficult to study in a live cell. In this talk we are interested as to how the activity of trans-membrane proteins modifies the physical properties of the membrane. In particular we will try to interpret two experiments were a proton pump, bacteriorhodopsin, is included into artificial vesicles. We will first investigate the possible contribution of a electrostatic potential build up across the membrane to its mechanical properties. We will then proceed with a more general description of the protein activity, where the equation of motion of the vesicle include an active noise. We show that the interpretation of one of the experiments require a change in the excess area (usually assumed constant for a passive vesicle) when the protein is activated and will then introduce the notion of tension renormalisation. We will then show a more recent experiment on the time correlation of the fluctuation of vesicle with reconstituted sodium-potassium pump (Na-KATPase).