Figure 1.

The formation of worm-like (WL) fibrils of β₂m (0.4 mg mL⁻¹ based on monomer; pH 3.6, 100 mM ammonium acetate; 20°C). β₂m monomer (open circles) was quantified over time by ESI-IMS-MS. The m/z spectra were normalized to the (M+H)⁺ ions of des-Arg bradykinin (1.4 μM, added immediately before analysis) at m/z 904 for monomer quantification (3). (Error bars) Standard deviation of the mean over three replicate experiments. WL fibril formation was monitored simultaneously by thioflavin-T fluorescence (thick solid line). A control in which β₂m (0.4 mg mL⁻¹) was incubated in 10 mM ammonium acetate (pH 3.6; 20°C) was also analyzed; thioflavin-T fluorescence confirmed that fibrils do not form under these conditions (thick shaded line). (Inset) Negative stain EM image of fully formed WL fibrils (the scale bar = 100 nm).