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Interaction of basic polypeptides with phospholipid vesicles was investigated by circular dichroism measurements. The polypeptides used were random copolymers of l-lysine with l-phenyl alanine, l-tyrosine and l-serine, i. e. (Lys,Phe)n, (Lys,Tyr)n and (Lys,Ser)n. The vesicles were prepared either from pure phosphatidylserine or from a mixture of phosphatidylserine with phosphatidyl-choline. It was found that (Lys, Phe)n undergoes a conformational transition from random coil to α-helix upon interaction with either pure phosphatidylserine vesicles or with mixed vesicles. (Lys,Tyr)n interacting with either phosphatidylserine or phosphatidylcholine vesicles undergoes a conformational transition from a random coil to β-structure. The copolymer (Lys,Ser)n interacting with either phosphatidylserine or phosphatidylcholine vesicles, and (Lys,Phe)n interacting with phosphatidylcholine vesicles remained in the random coil form.

The permselectivity of the ultrathin charged membranes to transport of identically charged ions and the structure of adsorbed polyelectrolyte monolayers from the measured transport was investigated. The ion transport was measured by means of the electrical current resulting from the electroreduction of the cationic depolarizers (Cd++, Cu++), diffusing to the surface. The diffusion of the ionic depolarizers to the mercury surface is impeded by the equally charged layer of polybases to an extent depending on their concentration and their structure in the surface and on the concentration of the supporting electrolyte in the bulk. The impeding effect of the adsorbed polybase monolayers was obtained from the ordinary polarographic diffusion current measurements and also from the current–time curves during the lifetime of single mercury droplets at selected constant potentials. The current–time curves also provide a means for determination of the diffusion coefficients or of the surface concentrations of the polybases.