title: Detection of populations of amyloid-like protofibrils with different physical properties.
abstract: We used tapping mode atomic force microscopy to study the morphology of the amyloid protofibrils formed at fixed conditions (low pH with high ionic strength) by self-assembly of the N-terminal domain of the hydrogenase maturation factor HypF. Although all protofibrils in the sample share a beaded structure and similar values of height and width, an accurate analysis of contour length and end-to-end distance and the comparison of experimental data with theoretical predictions based on the worm-like chain model show that two different populations of protofibrils are present. These populations are characterized by different physical properties, such as persistence length, bending rigidity and Young's modulus. Fluorescence quenching measurements on earlier globular intermediates provide an independent evidence of the existence of different populations. The finding that differences in mechanical properties exist even within the same sample of protofibrils indicates the presence of different subpopulations of prefibrillar aggregates with potentially diverse tendencies to react with undesired molecular targets. This study describes a strategy to discriminate between such different subpopulations that are otherwise difficult to identify with conventional analyses.
authors.affiliation: Department of Physics, University of Genoa, and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Genoa, Italy. relini@fisica.unige.it
authors.forename: Annalisa
authors.initials: A
authors.lastname: Relini
authors.forename: Silvia
authors.initials: S
authors.lastname: Torrassa
authors.forename: Riccardo
authors.initials: R
authors.lastname: Ferrando
authors.forename: Ranieri
authors.initials: R
authors.lastname: Rolandi
authors.forename: Silvia
authors.initials: S
authors.lastname: Campioni
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Chiti
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gliozzi
mesh_terms: D000682:Amyloid / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008301:Maleimides / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D009154:Mutation; D011312:Pressure; D017434:Protein Structure, Tertiary; D011721:Pyrenes / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013314:Stress, Mechanical; D013696:Temperature
chemical_list: D000682:Amyloid; D007477:Ions; D008301:Maleimides; D011721:Pyrenes; C043592:maleimide