title: On the mineral core of ferritin-like proteins: structural and magnetic characterization.
abstract: It is generally accepted that the mineral core synthesized by ferritin-like proteins consists of a ferric oxy-hydroxide mineral similar to ferrihydrite in the case of horse spleen ferritin (HoSF) and an oxy-hydroxide-phosphate phase in plant and prokaryotic ferritins. The structure reflects a dynamic process of deposition and dissolution, influenced by different biological, chemical and physical variables. In this work we shed light on this matter by combining a structural (High Resolution Transmission Electron Microscopy (HRTEM) and Fe K-edge X-ray Absorption Spectroscopy (XAS)) and a magnetic study of the mineral core biomineralized by horse spleen ferritin (HoSF) and three prokaryotic ferritin-like proteins: bacterial ferritin (FtnA) and bacterioferritin (Bfr) from Escherichia coli and archaeal ferritin (PfFtn) from Pyrococcus furiosus. The prokaryotic ferritin-like proteins have been studied under native conditions and inside the cells for the sake of preserving their natural attributes. They share with HoSF a nanocrystalline structure rather than an amorphous one as has been frequently reported. However, the presence of phosphorus changes drastically the short-range order and magnetic response of the prokaryotic cores with respect to HoSF. The superparamagnetism observed in HoSF is absent in the prokaryotic proteins, which show a pure atomic-like paramagnetic behaviour attributed to phosphorus breaking the Fe-Fe exchange interaction.
authors.affiliation: Dpto. de Física Aplicada I, Universidad del País Vasco - UPV/EHU, 48013 Bilbao, Spain and BCMaterials, Parque tecnológico de Zamudio, 48160 Derio, Spain. malu.gubieda@ehu.eus.
authors.forename: A
authors.initials: A
authors.lastname: García-Prieto
authors.affiliation: BCMaterials, Parque tecnológico de Zamudio, 48160 Derio, Spain. malu.gubieda@ehu.eus and Department of Physics, University of South Florida, Tampa, FL 33647, USA.
authors.forename: J
authors.initials: J
authors.lastname: Alonso
authors.affiliation: Dpto. de Inmunología, Microbiología y Parasitologa, Universidad del País Vasco - UPV/EHU, 48940 Leioa, Spain and Dpto. de Electricidad y Electrónica, Universidad del País Vasco - UPV/EHU, 48940 Leioa, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Muñoz
authors.affiliation: Dpto. de Electricidad y Electrónica, Universidad del País Vasco - UPV/EHU, 48940 Leioa, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Marcano
authors.affiliation: Dpto. de Inmunología, Microbiología y Parasitologa, Universidad del País Vasco - UPV/EHU, 48940 Leioa, Spain and Dpto. de Electricidad y Electrónica, Universidad del País Vasco - UPV/EHU, 48940 Leioa, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Abad Díaz de Cerio
authors.affiliation: BCMaterials, Parque tecnológico de Zamudio, 48160 Derio, Spain. malu.gubieda@ehu.eus.
authors.forename: R
authors.initials: R
authors.lastname: Fernández de Luis
authors.affiliation: SGIker, Universidad del País Vasco UPV/EHU, 48940 Leioa, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Orue
authors.affiliation: European Synchrotron Radiation Facility, 38000 Grenoble, France.
authors.forename: O
authors.initials: O
authors.lastname: Mathon
authors.affiliation: BCMaterials, Parque tecnológico de Zamudio, 48160 Derio, Spain. malu.gubieda@ehu.eus and Dpto. de Inmunología, Microbiología y Parasitologa, Universidad del País Vasco - UPV/EHU, 48940 Leioa, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Muela
authors.affiliation: BCMaterials, Parque tecnológico de Zamudio, 48160 Derio, Spain. malu.gubieda@ehu.eus and Dpto. de Electricidad y Electrónica, Universidad del País Vasco - UPV/EHU, 48940 Leioa, Spain.
authors.forename: M L
authors.initials: ML
authors.lastname: Fdez-Gubieda
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry; D003573:Cytochrome b Group / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000737:chemistry; D005293:Ferritins / Q000737:chemistry*; D006736:Horses; D006878:Hydroxides / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D036103:Nanotechnology / Q000379:methods*; D010758:Phosphorus / Q000737:chemistry; D020027:Pyrococcus furiosus / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D013053:Spectrophotometry; D013154:Spleen / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D003573:Cytochrome b Group; D006878:Hydroxides; D011994:Recombinant Proteins; D010758:Phosphorus; D005293:Ferritins; C018032:bacterioferritin; D007501:Iron