-peptide sequences and cylinder representations of nonglobally amphiphilic and globally amphiphilic .
Intensity of x-rays scattered from aqueous solutions of (black triangles) and (gray diamonds). A line of dots with a slope of is shown for comparison.
SAXS from an aqueous solution of , including form factor fits to models for a solid cylinder (orange), a solid cylinder with polydispersity in the radius (green), a flexible cylinder (blue), a hollow cylinder (purple), and a hollow cylinder with polydispersity included in the radius (red).
Schematic illustration of the hollow cylinder model used in form factor fitting to experimental scattering data where is the core radius, is the shell thickness, and is the length.
Experimental SAXS data from an aqueous solution of with form factor fits using a polydisperse hollow cylinder model to show the influence of (a) polydispersity of the core radius. A radial polydispersity of 5% is given by the orange line: 10% (green), 15% (blue), 21% (red), 25% (dark blue), and 30% (purple); (b) variation of the core radius on the fit: core radius of (blue line), (red), and (green); (c) variation of the shell radius on the fit: shell thickness of (blue), (red), and (green); and (d) variation of the radial composition. In this case the total diameter is fixed at and the core radius and the shell thickness are varied together. A core radius of is given by the purple line: (blue), (red), (orange), and (green); (e) the influence of cylinder length on the fit: (orange), (dark blue), (red), (purple), (green), and (blue). All other fit parameters are fixed.
SAXS from an aqueous solution of . The black diamonds show the experimental data. Green and blue lines indicate fitting results with and without a structure factor, , respectively, where the length of the cylinder was set at . The red line shows a form factor fit only, where the length of the hollow cylinder was given as . The polydisperse hollow cylinder form factor model gives a core radius of and a shell thickness of .
A transmission electron micrograph of a solution of -peptide stained with phosphotungstic acid (PTA) reveals the presence of uniform nanofibers. High contrast evident along the centerline of many nanofibers indicates hollow cores (arrows).
SAXS from aqueous solutions containing at (black triangles), (gray triangles), and (gray diamonds) including fits to a model that combines a form and structure factor. Intensity data (arbitrary units) is offset for clarity.
Parameters obtained from best-fit form factors.
Comparison of nanofiber dimensions obtained using SAXS and TEM analyses (Ref. 5).
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