FIGURE 6.

The synthetic polyQ peptide KK-Q32-KK forms oligomers with faster kinetics than a mutant htt fragment. A, in situ AFM experiments were performed with 5 μm HD53Q and KK-Q32-KK. B, the number of oligomeric and fibrillar aggregates formed by HD53Q and KK-Q32-KK was measured as a function of time. For KK-Q32-KK, the number of oligomers peaked (∼80 min) before dissipating, as the number of fibrils continued to increase. Large amorphous aggregates of KK-Q32-KK also appeared. Under these conditions, HD53Q only formed oligomers, which steadily increased in number as a function of time. C, ex situ AFM image of KK-Q32-KK sampled 5 h after incubation at 5 μm demonstrating that the peptide formed a mixture of aggregates consisting of oligomers (yellow arrows) and two distinct types of fibrils: narrower fibrils (∼1–2 nm tall, red arrows) and taller fibrils (∼5–7 nm tall, blue arrows).