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

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.

Design of Hollow Protein Nanoparticles with Modifiable Interior and Exterior Surfaces

“…The maximum particle dimension (D max )f rom the pair-distance distribution function (p(r)) was calculated to be 23 nm ( Figure 2B). Thed istribution pattern of p(r)w ith ah igh-r shifted peak was similar to that of ah ollow capsule particle such as the iron-storage protein apoferritin, [13] suggesting that the nanoparticle has ahollow inner space.Inaddition, alowresolution model composed of small beads (dummy atoms) was constructed from the SAXS data using the ab initio modeling program DAMMIF, [14] and the results indicated that the protein complex shape resembles as pherical hollow particle ( Figure 2B). Thed ummy-atom model and the manually designed rigid-body model of the nanoparticle superimposed well ( Figure S5 and S9), and I(q)s imulated from the rigid-body model roughly resembles I(q)o btained from the SAXS experiment (c 2 = 1.825) ( Figure S10).…”

Magnetic Nanoparticle Systems for Nanomedicine—A Materials Science Perspective

“…The structural features of several kinds of aqueous magnetic fluids [143][144][145][146], as well as surfactant/polymer solutions [147][148][149], which are used for magnetic nanoparticle stabilization in water, were investigated in detail by SANS (Figures 12 and 13). Additionally, magnetic nanoparticles with bio-macromolecules were successfully studied by SANS and SAXS [150,151] (Figure 14). Thus, investigations of magnetic fluid stability at various amounts of surfactants and aggregation of MNPs were undertaken by SAS for ferrofluids based on non-polar and polar (aqueous) carriers.…”

Design of Hollow Protein Nanoparticles with Modifiable Interior and Exterior Surfaces

“…The maximum particle dimension ( D max ) from the pair‐distance distribution function ( p ( r )) was calculated to be 23 nm (Figure B). The distribution pattern of p ( r ) with a high‐ r shifted peak was similar to that of a hollow capsule particle such as the iron‐storage protein apoferritin, suggesting that the nanoparticle has a hollow inner space. In addition, a low‐resolution model composed of small beads (dummy atoms) was constructed from the SAXS data using the ab initio modeling program DAMMIF , and the results indicated that the protein complex shape resembles a spherical hollow particle (Figure B).…”