title: Spatially resolved spectroscopic differentiation of hydrophilic and hydrophobic domains on individual insulin amyloid fibrils.
abstract: The formation of insoluble β-sheet-rich protein structures known as amyloid fibrils is associated with numerous neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. A detailed understanding of the molecular structure of the fibril surface is of interest as the first contact with the physiological environment in vivo and plays a decisive role in biological activity and associated toxicity. Recent studies reveal that the inherent sensitivity and specificity of tip-enhanced Raman scattering (TERS) renders this technique a compelling method for fibril surface analysis at the single-particle level. Here, the reproducibility of TERS is demonstrated, indicating its relevance for detecting molecular variations. Consequently, individual fibrils are systematically investigated at nanometer spatial resolution. Spectral parameters were obtained by band-fitting, particularly focusing on the identification of the secondary structure via the amide III band and the differentiation of hydrophobic and hydrophilic domains on the surface. In addition multivariate data analysis, specifically the N-FINDR procedure, was employed to generate structure-specific maps. The ability of TERS to localize specific structural domains on fibril surfaces shows promise to the development of new fibril dissection strategies and can be generally applied to any (bio)chemical surface when structural variations at the nanometer level are of interest.
authors.affiliation: Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Deckert-Gaudig
authors.affiliation: Chemistry Department Northwestern University, 2145 Sheridan rd, Evanston, IL 60208, USA.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Kurouski
authors.affiliation: Department of Chemical Engineering, Biotechnology and Environmental Technology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
authors.forename: Martin A B
authors.initials: MA
authors.lastname: Hedegaard
authors.affiliation: Institute for Physical Chemistry and Abbe School of Photonics, University of Jena, Helmholtzweg 4, 07743 Jena, Germany.
authors.forename: Pushkar
authors.initials: P
authors.lastname: Singh
authors.affiliation: Department of Chemistry, University at Albany, State University of New York, 1400 Washington Avenue, Albany, New York 12222, United States.
authors.forename: Igor K
authors.initials: IK
authors.lastname: Lednev
authors.affiliation: Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany.|Institute for Physical Chemistry and Abbe School of Photonics, University of Jena, Helmholtzweg 4, 07743 Jena, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Deckert
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D007328:Insulin / Q000737:chemistry* / Q000378:metabolism; D018625:Microscopy, Atomic Force; D054730:Protein Interaction Domains and Motifs; D013057:Spectrum Analysis / Q000379:methods; D013059:Spectrum Analysis, Raman
chemical_list: D000596:Amino Acids; D000682:Amyloid; D007328:Insulin