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The Schellman motif is a helix terminating structural motif in proteins, gained by adopting a left-handed helical (alphaL) conformation by the C-terminus residue. This results in a hydrogen bonding patter involving an intramolecular 6-1 interaction. The crystal structure of the Boc-Leu-Aib-Val-Gly-Leu-Aib-Val-OMe heptapeptide showes a 3sub10 helix terminated by a Schellman motif with Aib(6) having an alphaL - conformation.

Insertion of omega-amino acids into polypeptides is a convenient way of incorporating further methylene groups into peptide chains. Eight- and 11-residue peptides containing internal beta-Ala-gamma-Abu segments were examined as part of investigations into the effects of omega-amino acid insertion into helical peptide sequences. It was established that the beta-Ala-gamma-Abu segment can be easily accommodated into helical peptide structures with further bacbone carbon atoms forming small perturbations.

The solution structure of a model heptapeptide, Boc-Leu-Aib-Val-Ala-Leu-Aib-Val-OMe, was investigated by X-ray crystallography and nuclear magnetic resonance experiments. The results revealed a right-handed 3(sub10)-helical structure with a left-handed helical conformation at Aib(6) at the C-terminus, resulting in a 6 to 1 hydrogen bond involving the NH group. The NH group of the C-terminal residues 3-6 are hydrogen bonded, whereas residues 1-3 are solvent exposed, suggesting an alpha-helical structure.