Line thermodynamics: Adsorption at a membrane edge

We report a novel experimental study of line thermodynamics. Our system consists of detergent molecules adsorbing at the edges of freestanding lipid bilayers. Adsorption reduces the line tension T of the membrane edges. Measuring T as a function of the bulk detergent concentration C, we obtain a line adsorption isotherm. Using an extension of Gibbs's surface thermodynamics to lines, we estimate the "line excess density'' of adsorbants and the energy of adsorption per site.