Two Opposing d-Amino Acids Give Zigzag Hairpin Epitopes an Additional Kink to Create Antibody-Selective Peptide...

We have developed peptides that are able to distinguish between subgroups of polyclonal antibodies. These β-hairpin peptides act as conformational epitopes with specific shape and flexibility; they have been analyzed by NMR and CD spectroscopy, and have been shown to identify known disease markers. As a standalone mini β-sheet, a hairpin is stabilized by alternating pairs of hydrogen-bonded and non-bonded amino acids on its two opposing peptide strands. A single d mutation disrupts this secondary structure, the correlated double-d mutation of two opposing amino acids compensates for this destabilizing effect. The designed kink was introduced into both hydrogen-bonded and -non-bonded positions of an all-l hairpin that is a known conformational epitope in molecular recognition. Our peptides enabled the discrimination of different human rheumatoid arthritis autoantibodies in an ELISA assay.