title: Nanoscopic and photonic ultrastructural characterization of two distinct insulin amyloid states.
abstract: Two different conformational isoforms or amyloid strains of insulin with different cytotoxic capacity have been described previously. Herein these filamentous and fibrillar amyloid states of insulin were investigated using biophysical and spectroscopic techniques in combination with luminescent conjugated oligothiophenes (LCO). This new class of fluorescent probes has a well defined molecular structure with a distinct number of thiophene units that can adopt different dihedral angles depending on its binding site to an amyloid structure. Based on data from surface charge, hydrophobicity, fluorescence spectroscopy and imaging, along with atomic force microscopy (AFM), we deduce the ultrastructure and fluorescent properties of LCO stained insulin fibrils and filaments. Combined total internal reflection fluorescence microscopy (TIRFM) and AFM revealed rigid linear fibrous assemblies of fibrils whereas filaments showed a short curvilinear morphology which assemble into cloudy deposits. All studied LCOs bound to the filaments afforded more blue-shifted excitation and emission spectra in contrast to those corresponding to the fibril indicating a different LCO binding site, which was also supported by less efficient hydrophobic probe binding. Taken together, the multi-tool approach used here indicates the power of ultrastructure identification applying AFM together with LCO fluorescence interrogation, including TIRFM, to resolve structural differences between amyloid states.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology,7491 Trondheim, Norway.
authors.forename: Katarzyna Maria
authors.initials: KM
authors.lastname: Psonka-Antonczyk
authors.affiliation: Department of Physics, Norwegian University of Science and Technology,7491 Trondheim, Norway.
authors.forename: Julien
authors.initials: J
authors.lastname: Duboisset
authors.affiliation: Department of Physics, Norwegian University of Science and Technology,7491 Trondheim, Norway.
authors.forename: Bjørn Torger
authors.initials: BT
authors.lastname: Stokke
authors.affiliation: Bioengineering laboratory, RIKEN Institute, 2-1 Hirosawa, Wako-shi, Saitama 351 0198, Japan.
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Zako
authors.affiliation: Bioengineering laboratory, RIKEN Institute, 2-1 Hirosawa, Wako-shi, Saitama 351 0198, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Bioengineering laboratory, RIKEN Institute, 2-1 Hirosawa, Wako-shi, Saitama 351 0198, Japan.
authors.forename: Mizuo
authors.initials: M
authors.lastname: Maeda
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, Linköping 581 83, Sweden.
authors.forename: Sofie
authors.initials: S
authors.lastname: Nyström
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, Linköping 581 83, Sweden.
authors.forename: Jeff
authors.initials: J
authors.lastname: Mason
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, Linköping 581 83, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Hammarström
authors.affiliation: Department of Physics, Chemistry and Biology, Linköping University, Linköping 581 83, Sweden.
authors.forename: K Peter R
authors.initials: KPR
authors.lastname: Nilsson
authors.affiliation: Department of Physics, Norwegian University of Science and Technology,7491 Trondheim, Norway.
authors.forename: Mikael
authors.initials: M
authors.lastname: Lindgren
mesh_terms: D000682:Amyloid; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007328:Insulin / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D066329:Protein Aggregates; D013050:Spectrometry, Fluorescence; D013876:Thiophenes / Q000737:chemistry
chemical_list: D000682:Amyloid; D007328:Insulin; D066329:Protein Aggregates; D013876:Thiophenes