As an important part of the innate immune system of all organisms, antimicrobial peptides, are considered as a possible solution for fighting bacteria resistant to standard antibiotics.Crucial characteristic of peptide antibiotic, as drug candidate is its high selectivity, parameterized as the ratio of concentration causing 50% haemolysis (HC50) against erythrocytes and the minimal inhibitory concentration (MIC) against the reference bacterium Escherichia coli. Using the “Designer” algorithm adepantins were designed - highly selective artificial glycine and lysine rich peptides in predominant α helical conformation, having less than 50% homology of primary sequence to any known sequence of antimicrobial peptides. The algoritham used our database of anuran antimicrobial peptides with known selectivity index. Structure and activity of adepantins were experimentally and computationally tested in their monomeric, dimeric and fluorescently labelled form. Experimental investigations performed on different bacteria strains showed high selectivity of adepantins for Gram-negative bacteria ( MIC = 0.5 - 4 μM ), especially E. coli. In membrane permeabilization measurements, different membrane models were used and adepantins showed rapid permeabilization of both membranes of E. coli. These tests provided insight in their mode of action. All monomeric adepantins have exceptionally low haemolytic activity, while dimers expressed certain toxicity against host cells. It is proven that adepantins bind efficiently to the cell surface of the host cell membranes without subsequent membrane damage. Gathered results confirmed that adepantins are indeed highly selective artificial peptide antibiotics.