TY - JOUR
T1 - Magnetic properties and structural characterization of iron oxide nanoparticles formed by Streptococcus suis Dpr and four mutants
AU - Haikarainen, Teemu
AU - Paturi, Petriina
AU - Lindén, Johan
AU - Haataja, Sauli
AU - Meyer-Klaucke, Wolfram
AU - Finne, Jukka
AU - Papageorgiou, Anastassios C.
PY - 2011/6
Y1 - 2011/6
N2 - Streptococcus suis Dpr belongs to the Dps family of bacterial and archaeal proteins that oxidize Fe2+o Fe3+ to protect microorganisms from oxidative damage. The oxidized iron is subsequently deposited as ferrihydrite inside a protein cavity, resulting in the formation of an iron core. The size and the magnetic properties of the iron core have attracted considerable attention for nanotechnological applications in recent years. Here, the magnetic and structural properties of the iron 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 Mössbauer spectroscopy compatible with that of superparamagnetic ferrihydrite nanoparticles. However, all the mutants exhibited higher magnetic moments than the wildtype protein. Furthermore, measurement of the iron content with inductively coupled plasma mass spectrometry revealed a smaller amount of iron in the iron cores of the mutants, suggesting that the mutations affect nucleation and iron 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 iron 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 iron storage cavity could be exploited to selectively modify the magnetic properties of the iron core without affecting the structure of the protein and the geometry of the iron core.
AB - Streptococcus suis Dpr belongs to the Dps family of bacterial and archaeal proteins that oxidize Fe2+o Fe3+ to protect microorganisms from oxidative damage. The oxidized iron is subsequently deposited as ferrihydrite inside a protein cavity, resulting in the formation of an iron core. The size and the magnetic properties of the iron core have attracted considerable attention for nanotechnological applications in recent years. Here, the magnetic and structural properties of the iron 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 Mössbauer spectroscopy compatible with that of superparamagnetic ferrihydrite nanoparticles. However, all the mutants exhibited higher magnetic moments than the wildtype protein. Furthermore, measurement of the iron content with inductively coupled plasma mass spectrometry revealed a smaller amount of iron in the iron cores of the mutants, suggesting that the mutations affect nucleation and iron 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 iron 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 iron storage cavity could be exploited to selectively modify the magnetic properties of the iron core without affecting the structure of the protein and the geometry of the iron core.
KW - Ferritins
KW - Ferroxidase
KW - Magnetization
KW - Nanoparticles
KW - Streptococcal proteins
UR - http://www.scopus.com/inward/record.url?scp=80051543920&partnerID=8YFLogxK
U2 - 10.1007/s00775-011-0781-z
DO - 10.1007/s00775-011-0781-z
M3 - Article
C2 - 21487937
AN - SCOPUS:80051543920
SN - 0949-8257
VL - 16
SP - 799
EP - 807
JO - Journal of Biological Inorganic Chemistry
JF - Journal of Biological Inorganic Chemistry
IS - 5
ER -