Optical dynamometry to study phase transitions in lipid membranes.

The fluidity of the lipid matrix of cell membranes is crucial for the mobility of various inclusions like proteins. When the lipid bilayer undergoes phase transition from fluid-to-gel phase, the shear surface viscosity of the membrane diverges, thus hindering the motion of the membrane inclusions. On the other hand, the membrane bending stiffness drops down, and below the main phase transition, drastically increases with lowering the temperature.