Performance and Mechanisms of PropS-SH/HA Coatings in the Inhibition of Pyrite Oxidation.
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ABSTRACT:
SUBMITTER: Yang S
PROVIDER: S-EPMC8637958 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The mass-independent minor oxygen isotope compositions (?'17O) of atmospheric O2 and [Formula: see text] are primarily regulated by their relative partial pressures, [Formula: see text]/[Formula: see text] Pyrite oxidation during chemical weathering on land consumes [Formula: see text] and generates sulfate that is carried to the ocean by rivers. The ?'17O values of marine sulfate deposits have thus been proposed to quantitatively track ancient atmospheric conditions. This proxy assumes direct [Formula: see text] incorporation into terrestrial pyrite oxidation-derived sulfate, but a mechanistic understanding of pyrite oxidation-including oxygen sources-in weathering environments remains elusive. To address this issue, we present sulfate source estimates and ?'17O measurements from modern rivers transecting the Annapurna Himalaya, Nepal. Sulfate in high-elevation headwaters is quantitatively sourced by pyrite oxidation, but resulting ?'17O values imply no direct tropospheric [Formula: see text] incorporation. Rather, our results necessitate incorporation of oxygen atoms from alternative, 17O-enriched sources such as reactive oxygen species. Sulfate ?'17O decreases significantly when moving into warm, low-elevation tributaries draining the same bedrock lithology. We interpret this to reflect overprinting of the pyrite oxidation-derived ?'17O anomaly by microbial sulfate reduction and reoxidation, consistent with previously described major sulfur and oxygen isotope relationships. The geologic application of sulfate ?'17O as a proxy for past [Formula: see text]/[Formula: see text] should consider both 1) alternative oxygen sources during pyrite oxidation and 2) secondary overprinting by microbial recycling.
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Project description:The information presented is part of an investigation that seeks a better understanding of lipid oxidation in walnuts. The data shown regarding edible coating, are one of the strategies used to investigate the effect over oxidation stability. For the present experiments, unshelled walnuts were coated with different formulations, and then stored at 37 °C, 20% RH for 6 weeks. After that time, coated nuts were taken out, cold pressed to extract the oil and analysed. The main data obtained from the oil analysis of walnuts were acid value, peroxide value, and thiobarbituric acid reactive substances (TBARS). Data show the variation of the parameters during the storage time at 37 °C, considering the different formulations of edible coatings and the control. These data are relevant to walnuts exporters to have a comparison point.
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Project description:Designing intricate structures and searching for functional materials has attracted wide interest in nanoscience. Herein we have fabricated (NiFe)S2 pyrite mesocrystals in the form of nearly-single crystalline porous cubes, and studied their self-optimization to realize efficient activity toward water oxidation under electrochemical conditions. The growth mechanism of the mesocrystals was a non-classical mechanism, which was initiated by the formation of a large quantity of small nickel sulfide clusters, followed by the aggregation and transformation of these small clusters in an oriented manner. When these mesocrystals were tested for water oxidation under electrocatalytic conditions, the materials served as pre-catalysts and immediately self-optimized to form amorphous S-doped metal (oxy)hydroxides, which are the real catalytically active materials. As a result, the observed overpotential to reach a current density of 10 mA cm-2 on glassy carbon electrodes was less than 260 mV. The growth mechanism studied here may provide opportunities for constructing intricate sulfide structures, and the self-optimization process during water oxidation can inspire new thoughts on electrocatalysis.
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Project description:The process in which nanostructured surfaces mediate cell adhesion is not well understood, and may be indirect (via protein adsorption) or direct. We prepared Sr-doped hydroxyapatite (Sr1-HA) 3D nanorods (with interrod spacing of 67.3 ± 3.8, 95.7 ± 4.2, and 136.8 ± 8.7 nm) and 2D nanogranulate patterned coatings on titanium. Employing the coatings under the same surface chemistry and roughness, we investigated the indirect/direct role of Sr1-HA nanotopographies in the regulation of osteoblast adhesion in both serum-free and serum-containing Dulbecco's Modified Eagle/Ham's Medium. The results reveal that the number of adherent cells, cell-secreted anchoring proteins (fibronectin, vitronectin, and collagen), vinculin and focal adhesion kinase (FAK) denoted focal adhesion (FA) contact, and gene expression of vinculin, FAK, and integrin subunits (α2, α5, αv, β1, and β3), undergo significant changes in the inter-nanorod spacing and dimensionality of Sr1-HA nanotopographies in the absence of serum; they are significantly enhanced on the <96 nm spaced nanorods and more pronounced with decreasing interrod spacing. However, they are inhibited on the >96 nm spaced nanorods compared to nanogranulated 2D topography. Although the adsorption of fibronectin and vitronectin from serum are higher on 136.8 ± 8.7 nm spaced nanorod patterned topography than nanogranulated topography, cell adhesion is inhibited on the former compared to the latter in the presence of serum, further suggesting that reduced cell adhesion is independent of protein adsorption. It is clearly indicated that 3D nanotopography can directly modulate cell adhesion by regulating integrins, which subsequently mediate anchoring proteins' secretion and FA formation rather than via protein adsorption.
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Project description:Osteosarcoma (OS) is an aggressive bone tumor with strong invasiveness, rapid metastasis, and dreadful mortality. Chemotherapy is a commonly used approach for OS treatment but is limited by the development of drug resistance and long-term adverse effects. To date, OS still lacks the curative treatment. Herein, we fabricated pyrite-based nanoparticles (FeS2@CP NPs) as synergetic therapeutic platform by integrating photothermal therapy (PTT) and chemo-dynamic therapy (CDT) into one system. The synthetic FeS2@CP NPs showed superior Fenton reaction catalytic activity. FeS2@CP NPs-based CDT efficaciously eradicated the tumor cells by initiating dual-effect of killing of apoptosis and ferroptosis. Furthermore, the generated heat from FeS2@CP under near-infrared region II (NIR-II) laser irradiation could not only inhibit tumor's growth, but also promote tumor cell apoptosis and ferroptosis by accelerating •OH production and GSH depletion. Finally, the photothermal/NIR II-enhanced CDT synergistic therapy showed excellent osteosarcoma treatment effects both in vitro and in vivo with negligible side effects. Overall, this work provided a high-performance and multifunctional Fenton catalyst for osteosarcoma synergistic therapy, which provided a pathway for the clinical application of PTT augmented CDT.
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Project description:Polymeric coatings are commonly applied to impart functionality and colloidal stability to engineered nanoparticles. In natural environments, transformations of the coating can modify the particle transport behavior, but the mechanisms and outcomes of these transformations have not yet been thoroughly evaluated. This study investigates the photo-transformations of polyvinylpyrrolidone (PVP) coatings on gold nanoparticles (AuNPs) under ultraviolet (UV) irradiation, representing light exposure in surface waters or other sunlit environments, and the impact on the AuNP colloidal stability. Multiple orthogonal characterization methods were applied to interrogate UV-induced transformations and their consequences. Rapid oxidation of the PVP coating occurred upon UV exposure. The transformed PVP largely persisted on the AuNP surface, albeit in a collapsed polymer layer around the AuNP surface. This transformation resulted in drastically diminished colloidal stability of the AuNPs, consistent with loss of steric stabilization. While the residual coating modified the interaction of the AuNPs with calcium counterions, it did not prevent subsequent stabilization by humic acid. This study demonstrates the importance of both chemical and physical coating transformations on nanoparticles, and hence the need for orthogonal and complementary characterization methods to fully characterize the coating transformations. Finally, the specific transformations of the PVP-coated AuNPs investigated here are discussed more broadly with respect to generalizability to other polymer-coated NPs and the implications for their fate in sunlit or other reactive environments.
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Project description:Pyrite oxidation by mixed mesophilic acidophiles was conducted under conditions of controlled and non-controlled redox potential to investigate the role of sessile microbes in pyrite oxidation. Microbes attached on pyrite surfaces by extracellular polymeric substances (EPS), and their high coverage rate was characterized by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). The dissolution of pyrite was negligible if the redox potential was controlled below 650 mV (near the rest potential of pyrite), even though the bacteria were highly active and a high coverage rate was observed on pyrite surfaces. However, with un-controlled redox potential the rate of pyrite oxidation increased greatly with an increasing redox potential. This study demonstrates that sessile microbes play a limited role in pyrite oxidation at a redox potential below 650 mV, and highlight the importance of solution redox potential for pyrite oxidation. This has implications for acid mine drainage control and pyrite oxidation control in biometallurgy practice.
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Project description:Oxfenicine [S-2-(4-hydroxyphenyl)glycine] is transaminated in heart and liver to 4-hydroxyphenylglyoxylate, an inhibitor of fatty acid oxidation shown in this study to act at the level of carnitine palmitoyltransferase I (EC 2.3.1.21). Oxfenicine was an effective inhibitor of fatty acid oxidation in heart, but not in liver. Tissue specificity of oxfenicine inhibition of fatty acid oxidation was due to greater oxfenicine transaminase activity in heart and to greater sensitivity of heart carnitine palmitoyltransferase I to inhibition by 4-hydroxyphenylglyoxylate [I50 (concentration giving 50% inhibition) of 11 and 510 microM for the enzymes of heart and liver mitochondria, respectively]. Branched-chain-amino-acid aminotransferase (isoenzyme I, EC 2.6.1.42) was responsible for the transamination of oxfenicine in heart. A positive correlation was found between the capacity of various tissues to transaminate oxfenicine and the known content of branched-chain-amino-acid aminotransferase in these tissues. Out of three observed liver oxfenicine aminotransferase activities, one may correspond to asparagine aminotransferase, but the major activity could not be identified by partial purification and characterization. As reported previously for malonyl-CoA inhibition of carnitine palmitoyltransferase I, 4-hydroxyphenylglyoxylate inhibition of this enzyme was found to be very pH-dependent. In striking contrast with the kinetics of malonyl-CoA inhibition, 4-hydroxyphenylglyoxylate inhibition was not affected by oleoyl-CoA concentration, but was partially reversed by increasing carnitine concentrations.
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Project description:According to the literature, pyrite (FeS2) oxidation has been previously determined to involve thiosulfate as the first aqueous intermediate sulfur product, which is further oxidized to sulfate. In the present study, pyrite oxidation by Acidithiobacillus ferrooxidans was studied using electrochemical and metabolic approaches in an effort to extend existing knowledge on the oxidation mechanism. Due to the small surface area, the reaction rate of a compact pyrite electrode in the form of polycrystalline pyrite aggregate in A. ferrooxidans suspension was very slow at a spontaneously formed high redox potential. The slow rate made it possible to investigate the oxidation process in detail over a term of 100 days. Using electrochemical parameters from polarization curves and levels of released iron, the number of exchanged electrons per pyrite molecule was estimated. The values close to 14 and 2 electrons were determined for the oxidation with and without bacteria, respectively. These results indicated that sulfate was the dominant first aqueous sulfur species formed in the presence of bacteria and elemental sulfur was predominantly formed without bacteria. The stoichiometric calculations are consistent with high iron-oxidizing activities of bacteria that continually keep the released iron in the ferric form, resulting in a high redox potential. The sulfur entity of pyrite was oxidized to sulfate by Fe3+ without intermediate thiosulfate under these conditions. Cell attachment on the corroded pyrite electrode surface was documented although pyrite surface corrosion by Fe3+ was evident without bacterial participation. Attached cells may be important in initiating the oxidation of the pyrite surface to release iron from the mineral. During the active phase of oxidation of a pyrite concentrate sample, the ATP levels in attached and planktonic bacteria were consistent with previously established ATP content of iron-oxidizing cells. No significant upregulation of three essential genes involved in energy metabolism of sulfur compounds was observed in the planktonic cells, which represented the dominant biomass in the pyrite culture. The study demonstrated the formation of sulfate as the first dissolved sulfur species with iron-oxidizing bacteria under high redox potential conditions. Minor aqueous sulfur intermediates may be formed but as a result of side reactions.
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