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

Extensive evidence suggests that the self-assembly of amyloid-beta peptide (Abeta) is a nucleation-dependent process that involves the formation of several oligomeric intermediates. Despite neuronal toxicity being recently related to Abeta 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 Abeta 1-42 (Abeta42) aggregates along the self-assembly pathway. This multimethodological approach allowed elucidating the diverse assembly species formed during the Abeta aggregation process and was applied to the detailed investigation of the mechanism of Abeta42 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.