Fig. 5: Quantification of Aβ40 oligomer sizes by time-resolved light scattering.

a Light scattering signals, measured as photomultiplier tube voltages, for a 1.5 mM Aβ40 solution at pH 12 (cyan), a 1.5 mM Aβ40 solution after a rapid pH drop from 12 to 7.4 (red), and a pH 7.4 buffer alone (blue). Dashed line is a stretched-exponential fit to the pH drop data, as described in the text. Inset shows the data up to 50 ms. b Light scattering data recorded to 3600 s after a rapid pH drop. Insets compare the data up to 3.0 s (red) with pH drop data from a (orange). Dashed line is an empirical fit to a function that includes two stretched-exponential terms to describe curvature on 100 ms and 100 s time scales and a linear term to describe the long-time behavior, as described in the text. c Fits of the experimental data (dashed line) with simulations based on the coagulation model described in the text. Simulations parameters r₀ and E₀ were optimized for each value of the threshold size N_th, below which oligomer fusion rates r₀ are multiplied by the enhancement factor of E₀. Experimental and simulated light scattering signals are normalized to the signal from a 1.0 mM solution of monomeric Aβ40. d Dependences of the optimized values of r₀ and E₀ and the deviation between optimized simulations and experimental data on the assumed oligomer threshold size N_th. The best fit is obtained with N_th ≈ 16. Source data are provided as a Source data file.