AFM investigation of the aggregation behavior of Alzheimer´s disease Aβ peptides

Amyoid peptides Aβ40 and Aβ42 are directly related to the Alzheimer´s disease (AD) pathology. More specifically small alterations in the ratio Aβ42:Aβ40 have been shown to influence dramatically the synaptic function in vitro and in vivo. In this study we use Atomic Force Microscopy to investigate the morphology of the species formed during aggregation at different moments in time. In agreement with literature data, we found that a small increase of this ratio appears to delay the fibrilization process. Moreover, in the case of the Aβ42, known to be more pathogenic than Aβ40, small oligomers seem to coexist with higher molecular weight species from very early to very late moments in time. This suggests the continuous presence of intermediates that might have a synapto-toxic effect.