SAXS structural study of PrP^Sc reveals ~11 nm diameter of basic double intertwined fibers

Figures & data

Figure 1. (A) Coomassie-stained SDS-PAGE of the SHaPrP27–30 sample subjected to SAXS analysis. (B) After SDS-PAGE, a sample was electroblotted onto a PVDF membrane and blotted with antibody 3F4. (C) Negative stain TEM of the same sample.

Figure 2. SAXS data in log-linear (A) representations and fit results of the infinite cylinder model (R = 5 nm) with hard-sphere structure factor and generalized Porod slope of SHaPrP27–30 (1 mg/mL). In the log-log representation of the SAXS data. (B) fit results varying the radius of the cylinders between 2 and 8 nm are shown together with the generalized Porod contribution (black). The arrow in both graphs indicates the hump of the structure factor corresponding to 11.0 ± 0.2 nm.

Table 1. Overview of the SAXS fit results using the cylindrical model with hard sphere structure factor and generalized Porod slope

Geometric mean radius	$\overline{R}$ (nm)	2 ± 0	3 ± 0	4 ± 0	5 ± 0	6 ± 0	7 ± 0	8 ± 0
Geometric standard deviation	ΔR/$\overline{R}$	2.5 ± 0	2.5 ± 0	2.5 ± 0	2.5 ± 0	2.5 ± 0	2.5 ± 0	2.5 ± 0
Packing density	pHS	0.17 ± 0.01	0.19 ± 0.01	0.20 ± 0.01	0.21 ± 0.01	0.22 ± 0.01	0.22 ± 0.01	0.23 ± 0.01
Hard-sphere interaction radius	Rhs (nm)	5.39 ± 0.1	5.41 ± 0.1	5.46 ± 0.1	5.53 ± 0.1	5.51 ± 0.1	5.57 ± 0.1	5.59 ± 0.1
Background	B	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0
Gen. Porod constant	Cp	17.5 ± 0.3	17.7 ± 0.3	18.0 ± 0.3	18.3 ± 0.3	18.3 ± 0.3	18.4 ± 0.3	18.5 ± 0.3
Gen. Porod exponent	p	3.20 ± 0.02	3.18 ± 0.02	3.17 ± 0.02	3.18 ± 0.02	3.18 ± 0.02	3.18 ± 0.02	3.19 ± 0.02

Figure 3. Schematic representation of PrP^Sc basic fibers based on the information obtained from SAXS and negative stain TEM.