In vitroOligomerization and Fibrillogenesis of Amyloid-beta Peptides
The amyloid beta Ab(1–40) and Ab(1–42) peptides are the main components of the fibrillar plaques characteristically found in the brains affected by Alzheimer’s disease. Fibril formation has been thoroughly studied in vitro using synthetic amyloid peptides
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In vitro Oligomerization and Fibrillogenesis of Amyloid-beta Peptides Núria Benseny-Cases, Oksana Klementieva and Josep Cladera
Abstract The amyloid beta Aβ(1–40) and Aβ(1–42) peptides are the main components of the fibrillar plaques characteristically found in the brains affected by Alzheimer’s disease. Fibril formation has been thoroughly studied in vitro using synthetic amyloid peptides and has been described to be a nucleation dependent polymerization process. During this process, defined by a slow nucleation phase followed by a rapid exponential elongation reaction, a whole range of aggregated species (low and high molecular weight aggregates) precede fibril formation. Toxic species related to the onset and development of Alzheimer’s disease are thought to be found among these prefibrillar aggregates. Two main procedures are used to experimentally monitor fibril formation kinetics: through the measurement of the light scattered by the different peptide aggregates and using the fluorescent dye thioflavin T, which fluorescence increases when specifically interacting with amyloid fibrils. Reproducibility may, however, be difficult to achieve when measuring and characterizing fibril formation kinetics. This fact is mainly due to the difficulty in experimentally handling amyloid peptides, which is directly related to the difficulty of having them in a monomeric form at the beginning of the polymerization process. This has to do mainly with the type of solvent used for the preparation of the peptide stock solutions (water, DMSO, TFE, HFIP) and the control of determinant physicochemical parameters such as pH. Moreover, kinetic progression turns out to be highly dependent on the type of peptide counter-ion used, which will basically determine the duration of the nucleation phase and the rate at which high molecular weight oligomers are formed. Centrifugation and filtration procedures used in the J. Cladera () Biophysics Unit and Center of Studies in Biophysics, Department of Biochemistry and Molecular Biology, Faculty of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain e-mail: [email protected] N. Benseny-Cases ESRF, Polygone Scientifique Louis Néel, 6 rue Jules Horowitz, 38000 Grenoble, France e-mail: [email protected] O. Klementieva Instituto de Neuropatología, Feixa LLarga sn 08907, Hospitalet de LLobregat, Spain e-mail: [email protected] J. R. Harris (ed.), Protein Aggregation and Fibrillogenesis in Cerebral and Systemic Amyloid Disease, Subcellular Biochemistry 65, DOI 10.1007/978-94-007-5416-4_3, © Springer Science+Business Media Dordrecht 2012
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preparation of the peptide stock solutions will also greatly influence the duration of the fibril formation process. In this chapter, a survey of the alluded experimental procedures is provided and a general frame is proposed for the interpretation of the fibril formation kinetics, intended to integrate the results from the different experimental approaches. The significance of the different aggregated
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