Abstract

The general aim of the work was to explain the molecular mechanism of the interaction between selected, newly synthesised quaternary ammonium salts (N-alkoxycarbonylmethyl-N-alkyl-piperidinium chlorides) and model membrane. The proper selection of compounds studied enables the determination of the influence of particular structural elements of the molecule on the micellization process, interaction with phospholipids membrane and biological activity. The studies were performed in several stages: (1) the first one involved micellization in order to learn the amphiphilic properties of studied compounds; the isothermal calorimetric titration was used to determine the values of cmc and the enthalpy of micellization process; it was presupposed that micellization studies of surfactants can be useful in prognosis of their interaction with membranes; (2) the next one was connected with the mechanism of the interaction with model membrane; the influence of compounds studied on thermotropic phase behaviour of phosphatidylcholine membranes and the localization of the surfactants in the lipid bilayer were determined by means of differential scanning calorimetry and spectroscopy; (3) in order to get some insight into the relationship between the biological activity and structure the whole group of quaternary ammonium salts was tested on bacterial strains; the activity for the tested compound was estimated on the basis of the lowest concentration giving a lethal effect; then, the most active compounds were tested on bacterial biofilms; (4) then, from the obtained results, determination of relationships between biological activity of piperidinium salts, their micellar properties and the interaction with the model membranes.

The antimicrobial activity assay in comparing with the results of model studies permit to propose the structure of cationic surfactant exerting high antimicrobial activity. From practical point of view, it may have significance while synthesizing new compounds for biological application.