FT-IR approaches on amyloid fibril structure.

This review treats recent achievements of Fourier-transform infrared absorption spectroscopy on protein science, especially on amyloid fibril structure. It includes the brief explanation of theoretical background, description of related techniques, and recent applications to analysis of fibril structure. Concerns to theoretical background, successful analysis of Amide I in terms of transition dipole coupling between the C=O oscillators in peptide main chain has been described. The theory enables us to estimate a content of secondary structure in a protein. Related experimental techniques such as linear dichroism measurement, application of microscope, and isotope labeling, are introduced. The linear-dichroism measurement brings direct information on molecular orientation, microscope enables to treat a well-prepared particle, and isotope-label technique allows our structural discussion with one-residue resolution. Application of IR absorption spectroscopy and related techniques on amyloid fibril structure is reviewed. The model obtained is compared with protein native structure.