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

TL;DR

This study investigates how varying iron oxide content in magnetoferritin affects its structure in solution, revealing increased polydispersity and shell destabilization at higher loading factors through SAXS and SANS analysis.

Contribution

It provides new insights into the structural effects of iron loading on magnetoferritin using combined SAXS and SANS techniques.

Findings

Increased iron loading raises protein polydispersity.

Higher iron content causes structural changes in the protein shell.

Shell stability decreases significantly above a loading factor of ~150.

Abstract

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 analyzed 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.