Magnetic properties and structural characterization of iron oxide nanoparticles formed by XXXX Dpr and four mutants.

@entity11769 @entity596 @entity8798 @entity61248 @entity68
@entity11769 Dpr belongs to the Dps family of bacterial and archaeal proteins that oxidize @entity8798 to @entity596 to protect microorganisms from oxidative damage. The oxidized @entity68 is subsequently deposited as @entity61248 inside a protein cavity, resulting in the formation of an @entity68 core. The size and the magnetic properties of the @entity68 core have attracted considerable attention for nanotechnological applications in recent years. Here, the magnetic and structural properties of the @entity68 core in wild-type Dpr and four cavity mutants were studied. All samples clearly demonstrated a superparamagnetic behavior in superconducting quantum interference device magnetometry and M  ssbauer spectroscopy compatible with that of superparamagnetic @entity61248 nanoparticles. However, all the mutants exhibited higher magnetic moments than the wild-type protein. Furthermore, measurement of the @entity68 content with inductively coupled plasma mass spectrometry revealed a smaller amount of @entity68 in the @entity68 cores of the mutants, suggesting that the mutations affect nucleation and @entity68 deposition inside the cavity. The X-ray crystal structures of the mutants revealed no changes compared with the wild-type crystal structure; thus, the differences in the magnetic moments could not be attributed to structural changes in the protein. Extended X-ray absorption fine structure measurements showed that the coordination geometry of the @entity68 cores of the mutants was similar to that of the wild-type protein. Taken together, these results suggest that mutation of the residues that surround the @entity68 storage cavity could be exploited to selectively modify the magnetic properties of the @entity68 core without affecting the structure of the protein and the geometry of the @entity68 core.
