The circular dichroism spectra of polypeptides that correspond to the N-terminal domain and transmembrane M2 and M3 fragments of the α-subunit of nicotine acetylcholine receptor of Torpedo californica were measured in an aqueous medium and in the presence of trifluoroethanol. The β sheet for the N-terminal domain and the α helices for the M2 and M3 fragments were found to be their major structural elements. These results confirmed earlier ideas regarding the secondary structure of the domains based on predicting algorithms and indirect methods. © 1998 MAEe Cyrillic signK Hayκa/Interperiodica Publishing.