Nanoscale Heterogeneity of the Molecular Structure of Individual hIAPP Amyloid Fibrils Revealed with Tip‐Enhanced Raman Spectroscopy |
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Authors: | Corianne C vandenAkker Tanja Deckert‐Gaudig Michael Schleeger Krassimir P Velikov Volker Deckert Mischa Bonn Gijsje H Koenderink |
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Affiliation: | 1. FOM Institute AMOLF, XG, Amsterdam, The Netherlands;2. Leibniz Institute of Photonic Technology, Jena, Germany;3. Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, 55128, Germany;4. Soft Condensed Matter, Debye Institute for Nanomaterials Science, Department of Physics and Astronomy, Utrecht University, CC, Utrecht, The Netherlands;5. Unilever Research Labs, The Netherlands;6. Institute for Physical Chemistry and Abbe Center of Photonics, University of Jena, Jena, Germany |
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Abstract: | Type 2 diabetes mellitus is characterized by the pathological deposition of fibrillized protein, known as amyloids. It is thought that oligomers and/or amyloid fibrils formed from human islet amyloid polypeptide (hIAPP or amylin) cause cell death by membrane damage. The molecular structure of hIAPP amyloid fibrils is dominated by β‐sheet structure, as probed with conventional infrared and Raman vibrational spectroscopy. However, with these techniques it is not possible to distinguish between the core and the surface structure of the fibrils. Since the fibril surface crucially affects amyloid toxicity, it is essential to know its structure. Here the surface molecular structure and amino acid residue composition of hIAPP fibrils are specifically probed with nanoscale resolution using tip‐enhanced Raman spectroscopy (TERS). The fibril surface mainly contains unordered or α‐helical structures, in contrast to the β‐sheet‐rich core. This experimentally validates recent models of hIAPP amyloids based on NMR measurements. Spatial mapping of the surface structure reveals a highly heterogeneous surface structure. Finally, TERS can probe fibrils formed on a lipid interface, which is more representative of amyloids in vivo. |
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Keywords: | amylin islet amyloid polypeptides amyloid fibrils protein misfolding protein nanofibrils TERS |
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