Search

Mile Square Health Center (MSHC), a network of Federally Qualified Health Centers (FQHCs) run by the University of Illinois Hospital (UIH) in Chicago, established Drive-Thru and Walk-Up COVID-19 testing sites. The primary aim of the UIH/MSHC testing project was to increase testing capacity in the most affected, racial/ethnic minority communities. More than 7,500 tests were performed over a six-month period. Half of those who were tested were Black and Latinx residents. The majority of those tested at the Walk-Up sites were Black, while “Other” race group tended to get tested in Drive Thru testing sites. Latinx residents had the highest positivity rate, followed by Other race group. Younger age groups were more likely to have higher positivity rates. Overall, UH/MSHC testing results reflected the overall Chicago COVID-19 testing results. Our findings substantiate the need to advocate for equitable resource allocation to counter the disproportionate burden of COVID-19 infection among minority communities. FQHCs were shown to be an effective approach to reduce structural barriers to COVID-19 testing and subsequently reduce disparities. Going forward, FQHCs can be key to ensuring COVID-19 vaccine outreach and dissemination.

Graphene coated iron oxide nanoparticles were prepared using microemulsion method for removal of Cr(VI) ions from aqueous solutions. Plausible interactions between the material and Cr(VI) ions were explored after adsorption and explained by characterizing through various analytical techniques such as Raman spectroscopy, LIBS, FTIR, TEM, EDX, SEM, particle size and zeta-potential measurements which confirmed 20% crystalline nature of GCIO, nanorange (50 nm) size of nanoparticles and great thermal stability. A simple, sensitive and highly selective direct spectrophotometric method was used for the determination of trace levels of Cr(VI) and various experimental parameters, such as the effect of time, pH, adsorbent dose, chromium concentration, temperature and composition of nanoparticles were studied on the adsorption of chromium. The equilibrium sorption data were fitted to various adsorption isotherm models and the as prepared GCIO adsorbent was found to follow the pseudo second order kinetics (R2 = 0.97) and Freundlich model isotherm (R2 = 0.97) with high adsorption capacity (352.1126 mg/g) for Cr(VI) adsorption. The nanoadsorbents were also found to be fairly reusable.

The graphene-coated iron oxide (GCIO) was used for the removal of Pb2+ and As3+ ions from aqueous solution. For the characterization of GCIO, several techniques (FTIR, XRD, EDX, SEM, TEM, TGA, DSC and vibrating sample magnetometry) were used which indicated the interaction of Pb2+ and As3+ with adsorbent. In addition, the effects of adsorbate concentration, different composition of adsorbent, temperature, pH of the solution and contact time of adsorbate–adsorbent were studied. After analysis of these experiments, it was found that GCIO offered very fast removal of Pb2+ and As3+ with small amount of GCIO (0.09 g) in 100 mg/L adsorbate solution. The maximum removal of Pb2+ ions (up to 97.62%) was achieved when 100 mg/L standard solution of metal ion was treated with GCIO for 35 min at 45°C in weak acidic medium (5 pH). The adsorption of Pb2+ ions followed Freundlich model with high correlation coefficient 0.98 R2. In case of As3+ ions, maximum removal of metal ion (up to 86.62%) was attained when 100 mg/L adsorbate solution is treated with GCIO for 25 min in slightly acidic medium (6 pH) at 25°C. The adsorption of As3+ ions followed D–R model with 0.98 R2 value. The adsorption of both metal ions (Pb2+ and As3+) follows second-order kinetic model. The high percentage removal of metal ions with little quantity of GCIO confirmed that GCIO is an excellent, effective and economic adsorbent.

Bacterial metal reduction is an important biogeochemical process in anaerobic environments. An understanding of electron transfer pathways from dissimilatory metal-reducing bacteria (DMRB) to solid phase metal (hydr)oxides is important for understanding metal redox cycling in soils and sediments, for utilizing DMRB in bioremedation, and for developing technologies such as microbial fuel cells. Here we hypothesize that the outer membrane cytochromes OmcA and MtrC from Shewanella oneidensis MR-1 are the only terminal reductases capable of direct electron transfer to a hematite working electrode. Cyclic voltammetry (CV) was used to study electron transfer between hematite electrodes and protein films, S. oneidensis MR-1 wild-type cell suspensions, and cytochrome deletion mutants. After controlling for hematite electrode dissolution at negative potential, the midpoint potentials of adsorbed OmcA and MtrC were measured (−201 mV and −163 mV vs. Ag/AgCl, respectively). Cell suspensions of wild-type MR-1, deletion mutants deficient in OmcA (Δ omcA ), MtrC (Δ mtrC ), and both OmcA and MtrC (Δ mtrC– Δ omcA ) were also studied; voltammograms for Δ mtrC– Δ omcA were indistinguishable from the control. When the control was subtracted from the single deletion mutant voltammograms, redox peaks were consistent with the present cytochrome (i.e., Δ omcA consistent with MtrC and Δ mtrC consistent with OmcA). The results indicate that OmcA and MtrC are capable of direct electron exchange with hematite electrodes, consistent with a role as terminal reductases in the S. oneidensis MR-1 anaerobic respiratory pathway involving ferric minerals. There was no evidence for other terminal reductases operating under the conditions investigated. A Marcus-based approach to electron transfer kinetics indicated that the rate constant for electron transfer k et varies from 0.025 s −1 in the absence of a barrier to 63.5 s −1 with a 0.2 eV barrier.

Sorption of phosphate by Fe(III)- and Al(III)-(hydr)oxide minerals regulates the mobility of this potential water pollutant in the environment. The objective of this research was to determine the molecular configuration of phosphate bound on ferrihydrite at pH 6 by interpreting P K-edge XANES spectra in terms of bonding mode. XANES and UV–visible absorption spectra for aqueous Fe(III)–PO 4 solutions (Fe/P molar ratio = 0–2.0) provided experimental trends for energies of P(3p)–O(2p) and Fe(3d)–O(2p) antibonding molecular orbitals. Molecular orbitals for Fe(III)–PO 4 or Al(III)–PO 4 complexes in idealized monodentate or bidentate bonding mode were generated by conceptual bonding arguments, and Extended-Huckel molecular orbital computations were used to understand and assign XANES spectral features to bound electronic states. The strong white line at the absorption edge in P K-edge XANES spectra for Fe–PO 4 or Al–PO 4 systems is attributable to an electronic transition from a P 1s atomic orbital into P(3p)–O(2p) or P(3p)–O(2p)–Al(3p) antibonding molecular orbitals, respectively. For Fe–PO 4 systems, a XANES peak at 2–5 eV below the edge was assigned to a P 1s electron transition into Fe(4p)–O(2p) antibonding molecular orbitals. Similarly, a shoulder on the low-energy side of the white line for variscite corresponds to a transition into Al(3p)–O(2p) orbitals. In monodentate-bonded phosphate, Fe–O bonding is optimized and P–O bonding is weakened, and the converse is true of bidentate-bonded phosphate. These differences explained an inverse correlation between energies of P(3p)–O(2p) and Fe(3d)–O(2p) antibonding molecular orbitals consistent with a monodentate-to-bidentate transition in aqueous Fe(III)–PO 4 solutions. The intensity of the XANES pre-edge feature in Fe(III)-bonded systems increased with increasing number of Fe(III)–O–P bonds. Based on the similarity of intensity and splitting of the pre-edge feature for phosphate sorbed on ferrihydrite at 750 mmol/kg at pH 6 and aqueous Fe–PO 4 solutions containing predominantly bidentate complexes, XANES results indicated that phosphate adsorbed on ferrihydrite was predominantly a bidentate–binuclear surface complex.

The interaction of metalloproteins with oxides has implications not only for bioanalytical systems and biosensors but also in the areas of biomimetic photovoltaic devices, bioremediation, and bacterial metal reduction. Here, we investigate mitochondrial ferricytochrome c (Cyt c) co-sorption with 0.01 and 0.1 M phosphate on hematite (alpha-Fe2O3) surfaces as a function of pH (2-11). Although Cyt c sorption to hematite in the presence of phosphate is consistent with electrostatic attraction, other forces act upon Cyt c as well. The occurrence of multilayer adsorption, and our AFM observations, suggest that Cyt c aggregates as the pH approaches the Cyt c isoelectric point. In solution, methionine coordination of heme Fe occurs only between pH 3 and 7, but in the presence of phosphate this coordination is retained up to pH 10. Electrochemical evidence for the presence of native Cyt c occurs down to pH 3 and up to pH 10 in the absence of phosphate, and this range is extended to pH 2 and 11 in the presence of phosphate. Cyt c that initially adsorbs to a hematite surface may undergo conformation change and coat the surface with unfolded protein such that subsequently adsorbing protein is more likely to retain the native conformational state. AFM provides evidence for rapid sorption kinetics for Cyt c co-sorbed with 0.01 or 0.1 M phosphate. Cyt c co-sorbed with 0.01 M phosphate appears to unfold on the surface of hematite while Cyt c co-sorbed with 0.1 M phosphate possibly retains native conformation due to aggregation.

Electron transfer between redox active proteins and mineral oxides is important in a variety of natural as well as technological processes, including electron transfer from dissimilatory metal-reducing bacteria to minerals. One of the pathways that could trigger electron transfer between proteins and minerals is redox-linked conformation change. We present electrochemical evidence that mitochondrial cytochrome c (Mcc) undergoes significant conformation change upon interaction with hematite and indium-tin oxide (ITO) surfaces. The apparent adsorption-induced conformation change causes the protein to become more reducing, which makes it able to transfer electrons to the hematite conduction band. Although Mcc is not a protein thought to be involved in interaction with mineral surfaces, it shares (or can be conformed so as to share) some characteristics with multiheme outer-membrane cytochromes thought to be involved in the transfer of electrons from dissimilatory iron-reducing bacteria to ferric minerals during respiration. We present evidence that a 10.1 kDa monohoeme cytochrome isolated and purified from Acidiphilium cryptum, with properties similar to those of Mcc, also undergoes conformation change as a result of interaction with hematite surfaces.

The interaction of metalloproteins such as cytochromes with oxides is of interest for a number of reasons, including molecular catalysis of environmentally important mineral-solution electron transfer reactions (e.g., dehalogenations) and photovoltaic applications. Iron reduction by bacteria, thought to be cytochrome mediated, is of interest for geochemical and environmental remediation reasons. As a baseline for understanding cytochrome interaction with ferric oxide surfaces, we report on the interaction of mitochondrial cytochrome c (Mcc), a well-studied protein, with hematite (α-Fe 2 O 3 ) surfaces. Mcc sorbs strongly to hematite from aqueous solution in a narrow pH range corresponding to opposite charge on Mcc and hematite (between pH 8.5 and 10, Mcc is positively charged and hematite surfaces are negatively charged). Cyclic voltammetry of Mcc using hematite electrodes gives redox potentials characteristic of Mcc in a native conformational state, with no evidence for unfolding on the hematite surface. Atomic force microscopy imaging is consistent with a loosely attached adsorbate that is easily deformed by the AFM tip. In phosphate-containing solution, Mcc adhers to the surface more strongly. These results establish hematite as a viable material for electrochemical and spectroscopic characterization of cytochrome–mineral interaction.

The interaction of cytochromes (heme proteins) with mineral surfaces is important from an environmental perspective (e.g. heavy metal remediation and reductive dehalogenation reactions), for designing biosensors and bioanalytical systems, and for emerging photovoltaic applications. In addition, the cytochrome studied here shares properties with some cytochromes from Fe-reducing bacteria and its general behavior sheds light on how other cytochromes might behave during Fe(III) reduction. The objectives of this study were to characterize the direct electrochemistry and sorption mechanism of horse heart ferricytochrome c (a mitochondrial cytochrome referred to as Hcc) on hematite surfaces as a function of pH, time of sorption and ionic strength. Hcc sorption on hematite mainly occurs between pH 8 and 10, the pH range in which hematite surfaces and Hcc are oppositely charged. Calculated net attractive forces correspond closely with the pH range of peak sorption, suggesting that sorption is mainly electrostatically controlled. Hcc sorption with ionic strength is consistent with this conclusion. The pH-dependent conformation of Hcc sorbed on hematite appears to be different from that in solution as indicated by UV-visible spectroscopy and its more negative reduction potential compared to native Hcc. Sorption kinetics were rapid and pH-independent across the pH range 3–10 with slow conformational changes occurring at >60 h. Our results suggest that the electrostatic attraction of the cytochrome towards the surface orient the cytochrome for favorable electron transfer between the heme group of the cytochrome and hematite.

Phosphate sorption on Fe- and Al-oxide minerals helps regulate the solubility and mobility of P in the environment. The objective of this study was to characterize phosphate adsorption and precipitation in single and binary systems of Fe- and Al-oxide minerals. Varying concentrations of phosphate were reacted for 42 h in aqueous suspensions containing goethite, ferrihydrite, boehmite, or noncrystalline (non-xl) Al-hydroxide, and in 1:1 (by mass) mixed-mineral suspensions of goethite/boehmite and ferrihydrite/ non-xl Al-hydroxide at pH 6 and 22 degrees C. X-ray absorption near edge structure (XANES) spectroscopy was used to detect precipitated phosphate and distinguish PO4 associated with Fe(III) versus Al(III) in mixed-mineral systems. Changes in the full width at half-maximum height (fwhm) in the white-line peak in P K-XANES spectra provided evidence for precipitation in Al-oxide single-mineral systems, but not in goethite or ferrihydrite systems. Similarly, adsorption isotherms and XANES data showed evidence for precipitation in goethite/boehmite mixtures, suggesting that mineral interactive effects on PO4 sorption were minimal. However, sorption in ferrihydrite/non-xl Al-hydroxide systems and a lack of XANES evidence for precipitation indicated that mineral interactions inhibited precipitation in these binary mixtures.

Iron- and Al-(hydr)oxide minerals are important sorbents for retaining PO 4 in soils. Our objective was to determine the distribution of adsorbed PO, between ferrihydrite and boehmite in aqueous mixtures of these minerals. Phosphate was adsorbed in aqueous suspensions up to maximum concentrations of 1860, 850, and 1420 mmol kg -1 for ferrihydrite, boehmite, and 1:1 (by mass) mixtures of these minerals at pH 6. The solids were analyzed as moist pastes using P K-XANES (X-ray absorption near edge structure) spectroscopy. The adsorption isotherm for the mixed-mineral suspensions could essentially be described as a linear combination of Freundlich isotherm models for each single-mineral system, indicating negligible mineral interactive effects on PO 4 adsorption in the mixtures. X-ray absorption near edge structure spectra for PO 4 adsorbed on ferrihydrite or in ferrihydrite/ boehmite mixtures showed a pre-edge feature at approximately 2146 eV that was absent in boehmite systems. Linear combination fitting of the pre-edge region of XANES spectra for mixtures with average spectra for PO4 adsorbed on boehmite or ferrihydrite alone, indicated that 59 to 97% of the PO 4 was adsorbed on ferrihydrite in the mixtures. With increasing concentration of adsorbed PO 4 in the mineral mixtures, the concentration adsorbed on the ferrihydrite component increased linearly. Phosphate distribution trends in the mixtures suggested an affinity preference for ferrihydrite at the lowest adsorbed PO 4 concentration (100 mmol kg -1 minerals), no affinity preference for either mineral at intermediate concentrations (200 to 600 mmol PO 4 kg -1 ), and the possibility of a surface precipitate involving Al at the highest concentration (1300 mmol PO 4 kg -1 ).