Properties of Surfactants that Govern their Functions and Applications on Lipid Membranes

This work aims at a better understanding of the parameters and properties of surfactants that govern their specific biological functions and their suitability for applications related to biological membranes. First, the hypothesis is tested that membrane lysis starts when a surfactant has built up a critical level of curvature strain, that is detected as a chain disordering. This could be confirmed for many surfactants but some, mostly biosurfactants act by a locally focused, heterogeneous perturbation, which explains their enhanced antibiotic activity and selectivity. A model and protocol were established to obtain a volumetric characterization of micelles by pressure perturbation calorimetry. For some classic detergents studied so far, their chain packing was found to agree with that of bulk hydrocarbon. Finally, the effective charge and consequent membrane permeability were assessed by zeta potential measurements.Ph