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Quantification of the Concentration of Aβ42 Propagons during the Lag Phase by an Amyloid Chain Reaction Assay
journal contribution
posted on 2014-01-08, 00:00 authored by Paolo Arosio, Risto Cukalevski, Birgitta Frohm, Tuomas P. J. Knowles, Sara LinseThe
aggregation of the amyloid beta peptide, Aβ42, implicated
in Alzheimer’s disease, is characterized by a lag phase followed
by a rapid growth phase. Conventional methods to study this reaction
are not sensitive to events taking place early in the lag phase promoting
the assumption that only monomeric or oligomeric species are present
at early stages and that the lag time is defined by the primary nucleation
rate only. Here we exploit the high sensitivity of chemical chain
reactions to the reagent composition to develop an assay which improves
by 2 orders of magnitude the detection limit of conventional bulk
techniques and allows the concentration of fibrillar Aβ42 propagons
to be detected and quantified even during the lag time. The method
relies on the chain reaction multiplication of a small number of initial
fibrils by secondary nucleation on the fibril surface in the presence
of monomeric peptides, allowing the quantification of the number of
initial propagons by comparing the multiplication reaction kinetics
with controlled seeding data. The quantitative results of the chain
reaction assay are confirmed by qualitative transmission electron
microscopy analysis. The results demonstrate the nonlinearity of the
aggregation process which involves both primary and secondary nucleation
events even at the early stages of the reaction during the lag-phase.
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β42 Propagonsdetection limitβ42 propagonsgrowth phasenucleation eventsnucleation ratemonomeric peptides2 ordersLag PhaseConventional methodsoligomeric speciesfibril surfacemultiplication reaction kineticsbulk techniqueschain reaction assaychemical chain reactionsreagent compositionamyloid beta peptidechain reaction multiplicationAmyloid Chain Reaction AssayThe aggregationseeding dataaggregation processtransmission electron microscopy analysis
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