A pair of pyrene groups as a conformational probe for antiparallel β-sheet structure formed in cyclic peptides

Abstract

We have developed the utility of a pair of pyrene groups on L-1-pyrenylalanines (Pya) as a conformational probe for designed peptides composed of α-helices. Here, we expand the usefulness of the probing method to the antiparallel β-sheet structure formed in cyclic peptides. A pair of Pya residues were introduced into cyclic decapeptides, gramicidin S and its analogous peptide, at various positions which were involved in antiparallel β-sheet structures with amphiphilic character. When the two Pya residues were deployed on different β-strands, exciton interaction in circular dichroism spectra showed that the two pyrene rings were arranged with a left-handed twist. They were orientated in a right-handed sense on the same strand. The pyrene rings showed strong excimer emission. These results demonstrate that the behaviour of the pyrene probe is coincident with the left-handed orientation of two β-strands and the right-handed twist of a single β-strand in natural protein structures.