Effect of iron oxide loading on magnetoferritin structure in solution as revealed by SAXS and SANS

• Structure of synthetic biological macromolecule of magnetoferritin in aqueous solution is analysed by small-angle synchrotron X-rays (SAXS) and neutrons (SANS) scattering.
• With an increase loading factor (the average number of iron atoms per protein), the scattering curves exhibit a relative increase in the total scattered intensity, a partial smearing and a shift of the match point in the SANS contrast variation data.
• At loading factors above ∼150, the apoferritin shell undergoes structural changes, which is strongly indicative of the fact that the shell stability is affected by iron oxide presence.

Synthetic biological macromolecule of magnetoferritin containing an iron oxide core inside a protein shell (apoferritin) is prepared with different content of iron. Its structure in aqueous solution is analysed by small-angle synchrotron X-ray (SAXS) and neutron (SANS) scattering. The loading factor (LF) defined as the average number of iron atoms per protein is varied up to LF = 800. With an increase of the LF, the scattering curves exhibit a relative increase in the total scattered intensity, a partial smearing and a shift of the match point in the SANS contrast variation data. The analysis shows an increase in the polydispersity of the proteins and a corresponding effective increase in the relative content of magnetic material against the protein moiety of the shell with the LF growth. At LFs above ∼150, the apoferritin shell undergoes structural changes, which is strongly indicative of the fact that the shell stability is affected by iron oxide presence.

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