The
fibril formation of the neurodegenerative peptide amyloid β
(Aβ42) is sensitive to solution conditions, and several proteins
and peptides have been found to retard the process. Aβ42 fibril
formation was followed with ThT fluorescence in the presence of polyamino
acids (poly-glutamic acid, poly-lysine, and poly-threonine) and other
polymers (poly(acrylic acid), poly(ethylenimine), and poly(diallyldimethylammonium
chloride). An accelerating effect on the Aβ42 aggregation process
is observed from all positively charged polymers, while no effect
is seen from the negative or neutral polymers. The accelerating effect
is dependent on the concentration of positive polymer in a highly
reproducible manner. Acceleration is observed from a 1:500 polymer
to Aβ42 weight ratio and up. Polyamino acids and the other polymers
exert quantitatively the same effect at the same concentrations based
on weight. Fibrils are formed in all cases as verified by transmission
electron microscopy. The concentrations of polymers required for acceleration
are too low to affect the Aβ42 aggregation process through increased
ionic strength or molecular crowding effects. Instead, the acceleration
seems to arise from the locally increased Aβ42 concentration
near the polymers, which favors association and affects the electrostatic
environment of the peptide
