Conductance properties of des-Aib-Leu-des-Pheol-Phe-alamethicin in planar lipid bilayers

An alamethicin analogue in which all the amino-isobutyric acid and the C-terminal Pheol residues were replaced with Leu and an amidated Phe, respectively, has been synthesized. The purpose was to remove the ambiguity of a partial 3 10 helical character in alamethicin and thus, to study the conductance properties of a virtually full α helical rod modelling the natural voltage-dependent ionic channels. Macroscopic and single-channel experiments are consistent with the ‘barrel-staves’ model. The sequence of the conductance ratios of the sub-levels is very similar to the alamethicin one. The main difference lies in the very short-lived fluctuations displayed by the new analogue and is discussed in terms of helical conformation and length.