Kinetic characterization of amyloid-beta 1-42 aggregation with a multimethodological approach

Extensive evidence suggests that the self-assembly of amyloid-beta peptide (A beta) is a nucleation-dependent process that involves the formation of several oligomeric intermediates. Despite neuronal toxicity being recently related to A beta soluble oligomers, results from aggregation studies are often controversial, mainly because of the low reproducibility of several experimental protocols. Here a multimethodological study that included atomic force microscopy (AFM), transmission electron microscopy (TEM), fluorescence microscopy (FLM), mass spectrometry techniques (matrix-assisted laser desorption/ionization time-of-flight [MALDI-TOF] and electrospray ionization quadrupole time-of-flight [ESI-QTOF]), and direct thioflavin T (ThT) fluorescence spectroscopy were enabled to set up a reliable and highly reproducible experimental protocol for the characterization of the morphology and dimension of A beta 1-42 (A beta 42) aggregates along the self-assembly pathway. This multimethodological approach allowed elucidating the diverse assembly species formed during the A beta aggregation process and was applied to the detailed investigation of the mechanism of A beta 42 inhibition by myricetin. In particular, a very striking result was the molecular weight determination of the initial oligomeric nuclei by MALDI-TOF, composed of up to 10 monomers, and their morphology by AFM.