Ferritins are ubiquitous iron storage proteins in living systems. Although much is known about the iron deposition process in ferritin and a mechanism has been developed, several important issues still remain unknown. One lingering question is the less than stoichiometric quantities of hydrogen peroxide detected in previous studies on animal ferritins. Extensive experimental data on identifying the species in competition for peroxide equivalents point to a surprising conclusion that H2O2 generated in the ferroxidase reaction is consumed by amine buffers that are commonly employed in in vitro ferritin studies, while non-nitrogen containing buffers, such as acetate, phosphate, and carbonate, do not react with H2O2. The effects of amine buffer oxidation on the Fe2+/O2 stoichiometry, the kinetics and the molecular mechanism of iron deposition are discussed. The ~2 nm ferritin shell surrounding the ~4000 Fe(O)OH mineral core was originally thought to isolate the core from the environment. However, synthesized Co- and Mn(O)OH cores in horse spleen and bacteria ferritins are shown to be rapidly reduced by ascorbic acid and horse spleen ferritin containing a reduced Fe(II) core (Fe(II)-HoSF) presumably without direct contact. Further experiments demonstrate that both Fe(II)-HoSF and Co-/Mn-ferritins bind to gold electrodes and exchange electrons through the metallic conductor. These results provide the first direct evidence for electron transfer (ET) through the ferritin shell. The nature of the ET pathway is further investigated by loading iron into native and recombinant ferritins using large oxidants that are too big to enter the ferritin interior and must accept electrons from Fe2+ through this pathway. Experimental results suggest that the endogenous redox center in heteropolymeric animal ferritins and the heme groups in bacteria ferritins mediate ET through the protein shell. Finally, the diffusion properties of ferritin pores are examined toward iron (2+ and 3+) and anion transfer. Iron transfer is studied by the formation of Prussian blue ([FeIIFeIII(CN)6]-) encapsulated in the ferritin cavity, and is consistent with a binding-dissociation model proposed previously for iron transfer through the three-fold channels. When native HoSF is reduced by methyl viologen in saline solutions, small anions such as F-, Cl-, and Br , accumulate in the ferritin interior while phosphate is released. No anion transfer is observed during the reduction of reconstituted HoSF with no phosphate in the core. The possibility of ferritin as an anion pump in vivo is proposed.

Sulfur dioxide (SO₂), a well-known pollutant emitted from fossil fuel combustion, has major adverse health and environmental impacts. It is harmful at low concentration with a permissible exposure limit of two ppm for the eight-hour time-weighted average (TWA) value. Fortunately, its atmospheric concentration, like other air pollutants, has gradually reduced in Canada in the past years. However, despite the well-established flue gas desulfurization technologies, they have the disadvantages of being energy-intensive, not very efficient to achieve very low concentrations (at ppm level) and they operate at high temperatures. Moreover, emission standards are becoming more stringent. Novel methods are therefore investigated to capture SO₂, such as adsorption processes using zeolites and metal oxides (e.g., Iron (Fe) and Vanadium (V) based) which tend to sustain wide ranges of temperatures and pressures. Graphene oxide (GO) was also shown to physisorb SO₂ at low temperatures. In this work, we propose to metal functionalize GO as a step forward on the path for efficient SO₂ capture, by promoting the SO₂ oxidation reaction into sulfur trioxide (SO₃) for increased capacity due to a possible higher affinity with the surface. The GO has a high surface area, high porosity, and controllable surface chemistry. The aim is to achieve outlet concentration of SO₂ as low as 1 ppm through combined physisorption and reaction promoted that the presence of GO and metal, at low operating temperature. Iron oxide functionalized GO was synthesized using two different techniques: a polyol process (GO-FeₓOᵧ-P) and using a hydrolysis method (GO-FeₓOᵧ-H). The characterization analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), performed on the materials before and after SO₂ reaction show changes on the surface due to metal adding and to the sulfur capture. The breakthrough curves and the capacity calculations of the performed experiments have shown that with the addition of FeₓOᵧ on the surface of GO, the capturing capacity increases by a factor of three to four, indicating a possible change in the capturing mechanism. The evaluation of the temperature effect (from room temperature to 100℃) showed an increasing trend in the capture capacity for SO₂ with an increase in temperature, for both functionalized and non-functionalized GO, indicating it is not driven only by surface adsorption. The presence of sulfur species captured from the gas stream has been confirmed by energy-dispersive X-ray (EDXS) analysis. The future work would be focused on the investigation of the mechanisms and capturing phenomenon and the regeneration step for the materials in order to further improve the capturing capacity and process applicability.