Local orientational disorder in peptide fibrils probed by a combination of residue-specific 13C-18O labelling, polarised infrared spectroscopy and molecular combing.

A novel combination of site-specific isotope labelling, polarised infrared spectroscopy and molecular combing reveals local orientational ordering in the fibril-forming peptide YTIAALLSPYSGGRADS. Use of (13)C-(18)O labelled alanine residues demonstrates that the N-terminal end of the peptide is incorporated into the cross-beta structure, while the C-terminal end shows orientational disorder.