Aggregation of spin-labeled alamethicin in low-polarity solutions as studied by PELDOR spectroscopy

Alamethicin is a 20-residue antibiotic peptide. Interest in studying alamethicin stems from its ability to form conducting channels in biological membranes, thus changing their permeability. Although such channels in artificial and biological membranes have been well documented (see, e.g., [1, 2] and references therein), available reliable data are still insufficient to elucidate the mechanism of action of alamethicin on the properties of membranes. Therefore, it is of interest to study the self-aggregation of alamethicin molecules in media mimicking the membrane surface and interfacial layer, for example, in polar and nonpolar media. One approach to studying peptide self-aggregation in solutions is the spin label method in combination with CW ESR and pulsed ESR electron–electron double resonance (PELDOR). In this work, using these methods, we obtained the first reliable structural data on alamethicin aggregates in nonpolar media.