Small-angle scattering of apoferritin in solution

Native, undried, crystalline apoferritin, prepared from ferritin, was studied in aqueous solution (0.173–4.65%) by the X-ray small-angle method. Fourier transformation of the intensity distribution of the scattering curve of the apoferritin showed a density distribution corresponding to a hollow sphere with ri′ = 35.5 Å and ra′ = 62.7Å. The molecular weight of apoferritin was estimated as 462000 from measurements of the absolute intensity of the scattering. The molecular volume of the hydrated protein shell, derived from the invariant, is 82.5·104 Å3 and derived from the dimensions of the hollow sphere, is 84.0·104 Å3. The hydration was calculated from comparison with the volume in the non-hydrated state (57.4·104 Å3), as 0.327 g water per g protein