Membrane Properties close to the Lipid Phase Transition
Close to the main phase transition of the lipid we observe a dramatic increase in the membrane shear surface viscosity of more than two orders of magnitude (see Box - red triangles) which is a quantitative demonstration of the critical behavior of membrane viscosity near the fluid-to-gel transition of the lipid membrane.
In the gel phase (T<Tm) we probed the membrane elasticity by means of manipulating two particles with almost point contact with the membrane. The particles are displaced by means of a double optical trap (FRP - radiation pressure force) thus inducing an out-of-plane deformation (bending) of the membrane. For details see (1, 2).
We interpret the membrane response as mainly being due to curvature elasticity. The experiments allowed us to directly measure the curvature modulus (see Box - blue open circles) of a solidified membrane and to characterize its pretransitional behavior.
Bending elasticity and surface viscosity of a membrane close to the temperature of phase transition, Tm, of the lipid (DMPC). For details see (2).