Structural Aspects of the Growth Mechanism of Copper Nanoparticles Inside Apoferritin

CEOLÍN, M.; GÁLVEZ, N.; SÁNCHEZ, P.; FERNÁNDEZ, B.; DOMÍNGUEZ-VERA, J.M.

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY

Año: 2008 vol. 2008 p. 795 - 801

1434-1948

It is well known that some of the metal ions remain bound to apoferritin when incubating apoferritin with metal ions. In this study a structural insight, from X-ray absorption spectroscopy (XAS) and small angle X-ray scattering (SAXS) experiments, into the mechanism of inorganic core formation is presented. The results indicate that, in the case of CuII at pH 8, the metal ions bound to apoferritin are in fact CuII oxide/ hydroxide. This CuII species does not react with the CuII-specific TTMAPP, traditionally used to detect CuII, because TTMAPP is too large to penetrate the apoferritin channel and interact with the metal ions. EXAFS results suggest that the CuII precursor can be described as an amorphous network of oxygen/hydroxide-coordinating polyhedra surrounding the copper ions. XAS results demonstrate that this CuII-oxide/ hydroxide species is completely converted into zero-valent Cu nanoparticles when treated with NaBH4. Furthermore, a structural model for the final Cu0 nanoparticle is offered.II at pH 8, the metal ions bound to apoferritin are in fact CuII oxide/ hydroxide. This CuII species does not react with the CuII-specific TTMAPP, traditionally used to detect CuII, because TTMAPP is too large to penetrate the apoferritin channel and interact with the metal ions. EXAFS results suggest that the CuII precursor can be described as an amorphous network of oxygen/hydroxide-coordinating polyhedra surrounding the copper ions. XAS results demonstrate that this CuII-oxide/ hydroxide species is completely converted into zero-valent Cu nanoparticles when treated with NaBH4. Furthermore, a structural model for the final Cu0 nanoparticle is offered.