title: 2DIR spectroscopy of human amylin fibrils reflects stable β-sheet structure.
abstract: The aggregation of human amylin to form amyloid contributes to islet β-cell dysfunction in type 2 diabetes. Studies of amyloid formation have been hindered by the low structural resolution or relatively modest time resolution of standard methods. Two-dimensional infrared (2DIR) spectroscopy, with its sensitivity to protein secondary structures and its intrinsic fast time resolution, is capable of capturing structural changes during the aggregation process. Moreover, isotope labeling enables the measurement of residue-specific information. The diagonal line widths of 2DIR spectra contain information about dynamics and structural heterogeneity of the system. We illustrate the power of a combined atomistic molecular dynamics simulation and theoretical and experimental 2DIR approach by analyzing the variation in diagonal line widths of individual amide I modes in a series of labeled samples of amylin amyloid fibrils. The theoretical and experimental 2DIR line widths suggest a "W" pattern, as a function of residue number. We show that large line widths result from substantial structural disorder and that this pattern is indicative of the stable secondary structure of the two β-sheet regions. This work provides a protocol for bridging MD simulation and 2DIR experiments for future aggregation studies.
authors.affiliation: Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States. lwang@chem.wisc.edu
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: Chris T
authors.initials: CT
authors.lastname: Middleton
authors.forename: Sadanand
authors.initials: S
authors.lastname: Singh
authors.forename: Allam S
authors.initials: AS
authors.lastname: Reddy
authors.forename: Ann M
authors.initials: AM
authors.lastname: Woys
authors.forename: David B
authors.initials: DB
authors.lastname: Strasfeld
authors.forename: Peter
authors.initials: P
authors.lastname: Marek
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Raleigh
authors.forename: Juan J
authors.initials: JJ
authors.lastname: de Pablo
authors.forename: Martin T
authors.initials: MT
authors.lastname: Zanni
authors.forename: James L
authors.initials: JL
authors.lastname: Skinner
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D006801:Humans; D058228:Islet Amyloid Polypeptide / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: D000682:Amyloid; D058228:Islet Amyloid Polypeptide