Fluctuation spectrum of fluid membranescoupled to an elastic meshwork: jump of the effective surface tension at the mesh size

摘要

We identify a class of composite membranes: fluid bilayers coupled to anelastic meshwork, that are such that the meshwork's energy is afunction $F_mathrm{el}[A_xi]$ extit{not} of the real microscopicmembrane area $A$, but of a extit{smoothed} membrane's area $A_xi$,which corresponds to the area of the membrane coarse-grained at the meshsize~$xi$. We show that the meshwork modifies the membrane tension$sigma$ both below and above the scale $xi$, inducing a tension-jump$Deltasigma=dF_mathrm{el}/dA_xi$. The predictions of our modelaccount for the fluctuation spectrum of red blood cells membranescoupled to their cytoskeleton. Our results indicate that thecytoskeleton might be under extensional stress, which would provide ameans to regulate available membrane area. We also predict an observabletension jump for membranes decorated with polymer "brushes''.