Ferritin iron mineralization proceeds by different mechanisms in MOPS and imidazole buffers

Solid-state electron transport in Mn-, Co-, holo-, and Cu-ferritins: Force-induced modulation is inversely linked to the protein conductivity

“…It was found that 550, 420, and 310 metal atoms were incorporated per Mn(III)-ferritin, Co(III)-ferritin, and Cu(II)-ferritin molecule, respectively. The iron contents of equine spleen holoferritin and apoferritin were also determined, and these were found to be 2660 and 23 atoms, respectively, that match well with the reported values [6,7,38]. Since the metal content was considerably higher in case of holoferritin (2660 Fe atoms) compared to the reconstituted ferritins ($300-550 metal atoms), while still the current obtained from holoferritin was less than that obtained from the Co(III)-ferritin and Cu(II)-ferritin, it follows that the extent of metal loading did not directly influence the order of the conductivities of the five ferritin systems.…”

“…Mn(III)-ferritin, Co(III)-ferritin, and Cu(II)-ferritin samples were prepared and characterized as previously described [11,15,16,25]. The Fe(III)-ferritin sample was prepared using a procedure reported by Snow et al [7]. The resulting Fe(III)-ferritin was characterized by transmission electron microscopy (TEM) where carbon-coated copper grid (300 mesh) was used (see Fig.…”

“…For Mn(III)-ferritin, the AMPSO buffer (50 mM AMP-SO, 50 mM NaCl, pH 8.9) and for Co(III)-ferritin, the MOPS buffer (25 mM MOPS, 50 mM NaCl, pH 8.5) were used. In case of Fe(III)-ferritin, 50 mM MOPS, 100 mM NaCl, pH 7.5 buffer was used in conformity with the previous reports [7,27]. To keep the ferritin samples in their most stable forms, different buffers had to be applied [15].…”

“…Ferritin has the shape of a hollow sphere with an outer diameter of $12 nm and a shell thickness of $2 nm [4,5]. The core can contain few thousand iron atoms starting from about 2000 [6,7] up to 4500 iron atoms [4] in form of ferrihydrite phosphate [(FeO-OH) 8 (FeOPO 3 H 2 )]. Ferritin is robust when adsorbed onto a solid support and functions well up to 85°C temperature in aqueous environments within a pH range 4.0-9.0 [8].…”

A Synthetic Peptide with the Putative Iron Binding Motif of Amyloid Precursor Protein (APP) Does Not Catalytically Oxidize Iron

“…In this process two Fe(II) bind simultaneously to the catalytic site of ferritin, which is commonly known as the ferroxidase site (FC), and they are oxidized by molecular oxygen at a high rate. This reaction has typically been measured by following the UV-visible absorbance spectrum of ferritin-bound Fe(III) between 300 nm and 500 nm [28]. Using this procedure a k cat  = 3.3 sec −1 has been reported for HuHF [26] which is comparable to the values reported by Duce et al for ceruloplasmin and not orders of magnitude lower as claimed by them [15].…”