TTR spheroid oligomers and protofibrils.

<p><b>A.</b> 1×1 µm² AFM height contrast image of a mixed population of spheroid oligomers and short protofibrils. Black arrows point out examples of spheroid oligomers with various shapes and sizes. <b>Inset,</b> magnified view of a protofibril displaying a stack-like arrangement of flat, disc-shaped oligomers reminiscent of annular origin. <b>B.</b> 1×1 µm² AFM height contrast image of a mixed population of spheroid oligomers and longer protofibrils. Black arrows point out examples of spheroid oligomers with various shapes and sizes. <b>Inset</b>, magnified view of a protofibril in which the underlying periodic structure is probably helical. <b>C.</b> Topographical molecular volume histogram of 341 (<i>n</i>) spheroid TTR oligomers. The numbers above the modes correspond to the mean values of gaussian fits.</p

Formation and disappearance of annular oligomers.

<p><b>A.</b> Dynamic light scattering spectra of native TTR and at given time points after the start of acidification where the emergence of a small population of larger particles follows a trend towards smaller apparent hydrodynamic radii (Rh_app). <b>B.</b> Time course of the apparent size of the different populations during aggregation and their corresponding weighted average. The arrows indicate the times points where images shown in C and D were taken. <b>C & D.</b> AFM images (phase contrast) of particles taken at 9 and 12 h respectively and where annular oligomers (C) and spheroid (D) oligomers can be observed. The inset represents a 50×50 nm topography image of the corresponding samples (height scale up to 2.5 nm) <b>E.</b> Height-contrast AFM image of annular oligomers undergoing transitions. <b>E.</b> Magnified view of fusing annular oligomers indicated in <i>D</i>. Height, amplitude and phase contrast images (left to right) are shown. Scale bar, 10 nm.</p

Model of TTR protofibril assembly and disassembly.

<p>Relevant dimensions and periodicity parameters of the intermediates are indicated where applicable. Length of the arrows scale with the hypothesized transition kinetics.</p

Disassembly of TTR protofibrils.

<p><b>A.</b> AFM height contrast image recorded after 1 minute of sample dilution into PBS. <b>B.</b> AFM height (top) and amplitude (bottom) contrast images recorded after 5 minutes of sample dilution into PBS. <b>C.</b> AFM height (top) and amplitude (bottom) contrast images recorded after 15 minutes of sample dilution into PBS. <b>Insets</b>, magnified image of a single annular oligomer (left) and a laterally-associated doublet of annular oligomers (right). <b>D.</b> Distribution of the diameter of annular oligomers observed during assembly (yellow) and disassembly (purple). <b>E.</b> Distribution of the topographical height of annular oligomers observed during assembly (yellow) and disassembly (purple).</p