Sigmoidal trends have been often observed in concentration-dependent plots and indicate a positive cooperative behaviour, i.e. an increased activity or interaction at higher concentrations of a substrate. In enzymatic catalysis, for instance, this indicates allosteric effects in which binding of a ligand to an allosteric site increases the binding affinity and/or enzymatic activity towards its substrate. Similarly, positive cooperativity in adsorption isotherms relate to an increased binding in proximity to other adsorbates. In the present case, an analogous situation is conceivable where already membraneincorporated EB molecules or EBn:M z+ complexes, in the presence of Na + , support further integration in an autocatalytic fashion. Accordingly, due to the observed time delay of ca. 30 min, "regular" or spontaneous incorporation must be associated with a substantial barrier. To describe the entire incorporation behaviour, we translated a kinetic model to a differential equation system accounting for the following key processes (Figure ; for detailed description of this model see SI section 4). First, EB binds from the bulk to the membrane surface according to a Langmuir-like adsorption process. To account for the initial burst, two binding modes are assumed, i.e. strongly bound species, which do not show any considerable desorption, and weakly bound ones, which desorb from the membrane interface. Second, the strongly surface-bound species can transfer into the membrane via two mechanisms: (a) a spontaneous Langmuirlike incorporation according to