(A) First neighbor distance distribution can be analytically derived for PC randomly distributed in different space dimensions (line, plane and volume). (B) Computing the dipolar coupling for these distributions gives rise to a non-oscillating signal V(t) that can be fitted with Equation (1). The fitting output D parameter recapitulates the expected dimensionality.

(A) ESE decay of 4-OH-TEMPO in solution fitted with Equation 1 (black solid line). (B) Output parameters of the fit. Concentration is in number of particles per cm3 (1 µM = 6e14 cm-3).

DEER signal probe protein condensation and alignment during amyloid formation.

(A) A fragment of the tau protein, referred to as tau187, used to form amyloid aggregates. (B) Amyloids aggregates are elongated filaments in which each protein monomer is stacked with a cross-beta sheet structure. Within each layer, a protein can take different conformations: model of full-length tau fibers made with heparin (derived from PDB 6qjh; upper structure) and of tau peptide VQIVYQ (derived from PDB 2ON9; lower structure). (C) TEM of tau187 aggregates. (D) THT fluorescence intensity of tau187 aggregation. The dash lines represent the times at which samples were flash-frozen for analysis. (E) D and α parameters extracted from fit at each time points. (F) D and α parameters for filaments made with different SL-tau:noSL-tau ratios. The x-axis represents the percentage of total protein that is labelled. SL-tau protein of labelled to unlabeled tau187. (G) D and α parameters for filaments made with tau187 labelled at different positions, for a SL-tau:noSL-tau ratio of 1:10. The raw DEER signals and their fits are presented in Figure S4, S5 and S6.

(A) amyloid filaments were modelled with a line where PC (blue balls) has a probability p to exist at each discrete locations spaced by 4.7 Å (blue circle). First neighbor distance distribution of PC was numerically calculated from this model and used to compute dipolar signal (B) for p=0.02 (dark pink) p=0.05 (light pink) and p=0.1 (lilac). D and α parameters were extract from fitting with Equation (1). (C) Fitting output parameter D when p is twice more (attraction) or less (repulsion) important in the vicinity of a PC. The vicinity extends to the 1st (light pink), 1st and 2nd (lilac) or 1st, 2nd and 3rd (blue) neighbors. (D) Misalignment is introduced by allowing each PC to move within a disk of radius, A. (E) The resulting distance distributions are converted into dipolar evolution times that are fitted with Equation (1). (C) and (E) are generated with p=0.1.

We compare heparin-induced tau187, heparin-induced tau-16, and tau16 seeded tau187.

(A) tau16 peptide can aggregate into amyloid filaments expected to be well packed. (B) Tau16 filaments can be used to seed tau187 peptide into amyloid filaments. (C) The DEER signal of tau filaments are fitted with Equation (1) (black line) to extract (D) the dimensionality and the (E) α parameters.