Low Concentrations Of Ag Research Articles

Microstructural and optical properties of nanostructured Al/Ag co-doped ZnO thin films (AgxAl0.03ZnO0.97-x) by spray pyrolysis for optoelectronic applications

Al/Ag co-doped ZnO (AgxAl0.03ZnO0.97-x, x = 0, 0.02, 0.04, 0.06, 0.08) thin films were prepared using a facile spray pyrolysis deposition route, and their microstructural and optical properties were investigated. Dislocation density reduced and film crystallinity improved with increasing Ag content. This correlated with strain relaxation (∼10−4) and crystallite size enlargement (>23 nm) at high Ag concentrations, as determined by the Scherrer, Williamson-Hall, Halder-Wagner, and Wagner-Agua approximations. The small Urbach energy (<321 meV) and narrow band gap (∼3 eV) observed at low Ag concentration (4 at.%) indicate less structural defects and disorder, and facilitate exciton dissociation with minimum recombination, respectively. The Moss, Herve and Vandamme, and the Ravindra and Gupta models exhibited high correlation between refractive index values (2.09–2.35). Thus, this study demonstrates the enormous potential of Al/Ag co-doping to advance the properties of ZnO films to suit the fabrication of optoelectronic devices, and create opportunities for commercialization.

Characterization of CuAg Alloys with Low Ag Concentrations.

Copper-based alloys designed to combine high electronic and thermal conductivities with high mechanical strength find a wide range of applications in different fields. Among the principal representatives, strongly diluted CuAg alloys are of particular interest as innovative materials for the realization of accelerating structures when the use of high-gradient fields requires increasingly high mechanical and thermal performances to overcome the limitations induced by breakdown phenomena. This work reports the production and optical characterization of CuAg crystals at low Ag concentrations, from 0.028% wt to 0.1% wt, which guarantee solid solution hardening while preserving the exceptional conductivity of Cu. By means of Fourier Transform Infrared (FTIR) micro-spectroscopy experiments, the low-energy electrodynamics of the alloys are compared with that of pure Cu, highlighting the complete indistinguishability in terms of electronic transport for such low concentrations. The optical data are further supported by Raman micro-spectroscopy and SEM microscopy analyses, allowing the demonstration of the full homogeneity and complete solubility of solid Ag in copper at those concentrations. Together with the solid solution hardening deriving from the alloying process, these results support the advantage of strongly diluted CuAg alloys over conventional materials for their application in particle accelerators.

Strong infiltrative HHC36 antimicrobial peptide/silver nanoparticles-loaded carboxymethyl chitosan/sodium alginate hydrogel for acne vulgaris therapy

Acne is a common chronic skin inflammatory disease closely related to Cutibacterium acnes (C. acnes), which affects the life quality of patients worldwide, especially adolescents and young adults. However, the physical barrier of the skin makes drugs difficult to infiltrate effectively into infected site, causing acne hard to cure and easy to recur. Herein, we developed an antibacterial skin dressing with strong infiltration of antibacterial agents which can co-delivery small-molecular antimicrobial agents through stratum corneum deeply into dermis, achieving high antimicrobial efficacy. The antibacterial dressings were constructed with carboxymethyl chitosan/sodium alginate (CMCS/SA) hydrogel loading with HHC36 (an antimicrobial peptide) and silver nanoparticles (AgNPs) conjugates (Ag–H2/CMCS/SA hydrogel). The released Ag–H2 from Ag–H2/CMCS/SA hydrogel can early infiltrate into dermis, co-delivery HHC36 and AgNPs due to the infiltration and targeting of HHC36, presenting the superior antibacterial effect compared to HHC36 or AgNPs alone and killing 100% C. acnes and 100% Staphylococcus epidermidis (S. epidermidis) at a very low concentration of Ag–H2 (15 μg ml−1 A g with 7.1 μg ml−1 HHC36). Meanwhile, Ag–H2/CMCS/SA hydrogel was biocompatible due to the natural polysaccharides carboxymethyl chitosan and sodium alginate. The HaCaT cells spread well in Ag–H2/CMCS/SA hydrogel. These results indicate that the co-delivery small-molecular antimicrobial agents is a promising strategy and Ag–H2/CMCS/SA hydrogel has a great potential in the therapy of acne.

In Situ Trace Element and Sulfur Isotope Composition of Pyrite from the Beiwagou Pb-Zn Deposit, Liaodong Peninsula, Northeast China: Implications for Ore Genesis

The Beiwagou Pb-Zn deposit, located in the western part of the Liaodong Peninsula, is a carbonate-hosted stratiform deposit with a Pb + Zn reserve of 0.08 Mt @ 4.14% (Pb + Zn). The orebodies occur as conformable layers and lenses and are strictly controlled by strata (the Paleoproterozoic Gaojiayu and Dashiqiao Formations) and lithology (plagioclase amphibolite and dolomitic marble). Given that previous studies have focused only on the mineralization features and mineralogy of deposits, herein, we report in situ trace element analyses of pyrite using LA-ICP-MS, together with in situ sulfur isotopes of pyrite, to constrain the composition, substitution mechanisms, source of sulfur, and sulfate reduction pathways of pyrite in the Beiwagou deposit. Based on pyrite morphology, texture, and chemistry, four pyrite types were identified: subhedral, porous-to-massive pyrite (Py1) related to chalcopyrite; subhedral, porous crushed pyrite (Py2) associated with fine-grained sphalerite; rounded and porous pyrite (Py3) related to the Zn-rich part of the laminated ore; and anhedral, porous-to-massive pyrite (Py4) associated with pyrrhotite, arsenopyrite, sphalerite, and galena. Py1 is characterized by high As, Ag, Cd, In, Au, Cu, and Zn concentrations and low Te, Bi, and Mo concentrations, whereas Py2 has high concentrations of Co and Ni and low concentrations of other trace elements, such as Cu, Zn, Bi, and Te. Py3 is characterized by elevated As concentrations, low Co, Ni, In, W, Te, and Tl concentrations, and varying Pb concentrations, whereas Py4 has low Ag, Cd, In, Zn, Cu, and Mn concentrations and varying W, Co, Ni, Pb, Sb, and As concentrations. Significant correlations between some elements in each pyrite type suggest substitution mechanisms, such as (Zn2+ + Cu2+ + Mn2+ + Cd2+) ↔ 2Fe2+, Ag+ + (Sb)3+ ↔ 2Fe2+, and (Te+ + Ag+) + Sb3+ ↔ 2Fe2+, and the existence of a negative correlation between Co and Ni implies competition between both elements. The strongly positive δ34S values (12.11‰–23.54‰) are similar to that of seawater sulfates and likely result from thermochemical sulfate reduction (TSR). In conclusion, the Beiwagou Pb-Zn deposit is a typical SEDEX deposit and mineralization likely occurred during diagenesis.

Selective and high capacity recovery of aqueous Ag(I) by thiol functionalized mesoporous silica sorbent

A simplified sol–gel method was developed for the preparation of thiol functionalized porous silica particles using (3-mercaptopropyl)-trimethoxy-silane (MPTMS) for co-gelation in the presence of micellar templates. The resulting short range ordered porous silica microparticles are exceptionally effective sorbents of aqueous Ag(I). The binding of aqueous Ag(I) is almost stoichiometric in the broad pH range between 4.0 and 9.0 even at low Ag(I) concentrations until reaching the limiting 238 mg g−1 sorption capacity. The sorbent displays high selectivity towards Ag(I), which was tested in the simultaneous presence of several different metal compounds. The practically complete recovery of Ag(I) and the regeneration of the sorbent was achieved by washing with a 10 mM Na2S2O3 solution. X-ray photoelectron spectroscopy (XPS) revealed that silver is not reduced on the surface of the sorbent. The reason for the strong and selective binding of Ag(I) is the formation of layered thiolate coordination compounds on the functionalized silica surface that display characteristically high stability even in the presence of other competing metal ions.

The impact of metallic nanoparticles on gut fermentation processes: An integrated metabolomics and metagenomics approach following an in vitro digestion and fecal fermentation model

Metallic nanoparticles (MNPs) are becoming widespread environmental contaminants. They are currently added to several food preparations and cause a fast-growing concern for human health. The present work aims to assess the impact of zinc oxide (ZnO), titanium dioxide (TiO2), and silver (Ag) nanoparticles (NPs) on the human gut metabolome and microbiome. Water samples spiked with two different concentrations of each MNPs were subjected to in-vitro gastrointestinal digestion and in-vitro large intestine fermentation. The effects of the treatments were determined through 16 S amplicon sequencing and untargeted metabolomics. Multi-omics data integration was then applied to correlate the two datasets. MNPs treatments modulated the microbial genera Bifidobacterium, Sutterella, Escherichia and Bacteroides. The treatments, especially the lower concentrations of Ag and ZnO, caused modulation of indole derivatives, peptides, and metabolites related to protein metabolism in the large intestine. Notably, these metabolites are implicated in ulcerative colitis and inflammatory bowel disease. TiO2 NPs treatment in all concentrations increased E.coli relative abundance and decreased the abundance of B. longum. Moreover, for TiO2, an enrichment in proinflammatory lipid mediators of arachidonic acid metabolites, such as prostaglandin E2 and leukotrienes B4, was detected. For all metals except TiO2, low NP concentrations promoted differentiated profiles, thus suggesting that MNPs aggregation can limit adverse effects on living cells.

Multiple-site Ag doping in Bi[formula omitted]Se[formula omitted]: Compositional crossover from substitution to intercalation as revealed by photoelectron diffraction and X-ray fluorescence holography

The local structure around Ag atoms in Ag-doped Bi2Se3 (AgxBi2−ySe3) was investigated by photoelectron diffraction and X-ray fluorescence holography to understand the manner of Ag atom doping. At a low Ag concentration (x=0.05), photoelectron diffraction indicated that Ag atoms occupied Bi substitution sites. However, a mere accumulation of holes via Ag substitution for Bi fails to explain the observed variation previously reported in the transport properties of Ag-doped Bi2Se3 with different x values. In particular, simple Ag substitution for Bi fails to explain the pinning of the Fermi level at the bottom of conduction band, as suggested by the observed transport properties. In the case of a high Ag concentration (x=0.2), photoelectron diffraction suggested that the Ag atoms occupied not only the substitutional Bi site but also multiple interstitial sites, namely, the octahedral site in the van der Waals interlayer and the interstitial site in the Se layer. Ag 3d photoelectron spectra revealed that the Ag atoms had the same oxidation state, +1, regardless of the type of occupied site. Furthermore, X-ray fluorescence holography was employed for a model-free local structural analysis that refined the exact locations of Ag atoms in the Bi2Se3 crystal lattice. The behavioral crossover documented herein from hole doping at the substitutional site to electron doping at multiple sites reasonably explains the dependence of electronic structures and transport properties of Ag-doped Bi2Se3 on dopant concentration.

Enhanced electrochromic properties of Ag-incorporated WO3 nanocomposite thin films

WO3 nanocomposite thin films, in which metal nanoparticles are incorporated into a WO3 matrix, offer an enhanced electrochromic response speed with color neutrality. This article reports the structural, optical, and electrochemical properties of Ag nanoparticle-incorporated electrochromic WO3 thin films with different concentrations. Room-temperature-sputtered thin films using composite targets with a low Ag concentration exhibited a random distribution of small nanoparticles. In contrast, in the film with a higher Ag concentration, the particles were merged, resulting in a single or polycrystalline phase. Surface plasmon resonance peaks were observed in the absorption spectra of the Ag–WO3 composite films, indicating the formation of metallic nanoparticles, which was also confirmed via high-resolution transmission electron microscopy. The optical bandgaps decreased gradually from 3.15 eV for WO3-δ to 3.02 and 2.99 eV for W0.97Ag0.03O3-δ and W0.91Ag0.09O3-δ thin films, respectively. The W0.91Ag0.09O3-δ thin film showed a faster switching time of 2.6 s for coloring and 4.8 s for bleaching with a higher coloration efficiency of 66.52 cm2/C than those of the WO3-δ thin film, which were 3.8 s, 6.8 s, and 58.68 cm2/C, respectively. However, transmittance modulation in the W0.91Ag0.09O3-δ thin film was inferior to that in the other films. Furthermore, the W0.91Ag0.09O3-δ thin films were black in the colored state, whereas the bare WO3-δ and W0.97Ag0.03O3-δ thin films were Prussian blue, suggesting the realization of color neutrality through the incorporation of Ag nanoparticles.

МЕДНО-ПОРФИРОВАЯ МИНЕРАЛИЗАЦИЯ ТАЛЬНИКОВОГО РУДНОГО ПОЛЯ (ОХОТСКИЙ СЕГМЕНТ ОХОТСКО-ЧУКОТСКОГО ВУЛКАНОГЕННОГО ПОЯСА)

The Talnikovoye ore field where previous academic research and exploration work revealed porphyry copper mineralization is described. Our data show that mineralization is confined to the intrusions of Turonian granodiorite and quartz diorite (91 Ma, U-Pb metohod), as well as the accompanying hydrothermal-explosive breccias. Biotite-epidote-chlorite propylites are widespread within the ore field; in the southern part, phyllic alteration is superimposed on the halo of K-feldspar alteration. The ore occurs in zones of intense quartz, chlorite-epidote-quartz (with chalcopyrite and molybdenite), sulfide-potassium feldspar-quartz (with chalcopyrite and bornite), and sulfide-quartz-sericite (with chalcopyrite) stockwork veining with copper-molybdenum mineralization. They are characterized by moderate concentrations of Cu (0.1–0.3 %, reaching 1.1 %) and Mo (up to 0.1 %), low concentrations of Au (up to 0.1 g/t) and Ag (up to 2.6 g/t) and have a Cu-Mo-(Au, Ag, Pb, Zn, Sb, As) geochemical signature. Fluid inclusion data suggest the formation of mineralized veinlet quartz during the magmatic-hydrothermal transition (430–150 °С) with solutions at high (50 wt % NaCl equiv.), medium and low concentration (5–18.9 wt % NaCl equiv.) involved under the cooling-dilution scenario. Values of the main geochemical indicators, such as Cu/Mo (30–60) and Cu/Au (&gt; 1 × 105) ratios allowed us to assign the Tal’nikovoye ore field to the porphyry copper-molybdenum type characteristic of continental-margin volcano-plutonic belts formed at the mafic island-arc basement. The geochemical parameters of porphyry granitoids indicate their formation in a setting of subduction-to-transform plate boundary transition.

Silver removal and microbial community structure in microbial fuel cells

AbstractBackgroundSilver (Ag) removal, electric current generation and the microbial community responsible were investigated in two replicate dual‐chamber microbial fuel cells (MFCs). The MFCs were inoculated with activated sludge and operated for electricity generation over 90 days.ResultsSilver was efficiently removed from synthetic wastewater at the cathode chamber of the MFC and the precipitated particles on the cathode electrode were verified as Ag using X‐ray diffraction and scanning electron microscopy analysis. The MFCs achieved a maximum power density of 1850 ± 25 mW m−2 and a maximum Ag removal of 99.8%. Furthermore, Illumina high‐throughput sequencing of bacterial 16S rRNA genes showed that both MFCs shared the same dominant bacterial phyla, namely Synergistetes, Bacteroidetes, Proteobacteria and Firmicutes, with bacteria belonging to Butyricicoccus, Petrimonas, Desulfomicrobium and Desulfovibrio and large numbers of unassigned genera.ConclusionsThe dual‐chamber MFCs provided an efficient method for concurrent Ag removal and energy generation, and effectively removed and recovered Ag from various wastewater streams even at low Ag concentrations. However, continued Ag precipitation on the electrode surface during long‐term operation could lead to a deterioration in the performance of the MFC and an increase in internal resistance. © 2022 Society of Chemical Industry (SCI).

In-situ investigation on hydrogenation-dehydrogenation of Pd–Ag alloy films

The present work reports on synthesis of Pd–Ag nano-composite films by magnetron co-sputtering and the structural changes in the alloy film during hydrogenation and dehydrogenation. Synchrotron X-ray diffraction is employed in-situ to reveal subtle structural changes occurring during hydrogenation and dehydrogenation processes, an aspect not investigated so far. It is revealed that the nanocomposite film having 88 at% Pd shows the formation of α-phase as an intermediate phase, however, completion of the hydrogenation process yields only β-phase. No β-phase formation is observed in nanocomposite thin film containing 54 at% of Pd, suggesting the suppression of formation of β-phase with increase in Ag concentration. On dehydrogenation, the peak returns to its original position i.e. the value before hydrogenation. The data also demonstrated that the addition of Ag in Pd results in complete removal of dissolved hydrogen thereby eliminates the problem of hysteresis. The study shows that the lower concentrations of Ag in Pd are better in terms of extent of peak-shift on hydrogenation/dehydrogenation and faster response/recovery kinetics.

Recycling of solar photovoltaic panels: Techno-economic assessment in waste management perspective

This work assessed the economic sustainability of photovoltaic panels (PV) recycling. The PV throughout and silver (Ag) concentration in PVs are the main factor affecting recycling. For high Ag concentrations (0.2%), the recycling is sustainable without PV recycling fee if the PV throughput is higher than 18,000 t/yr. Lower processing volumes enable sustainability only with recycling fees from 0% up to 46% of the total annualized costs in the throughput range 18,000–9000 t/yr. For low Ag concentrations (0.05%) recycling fees are instead always needed to achieve profitability , unless the throughput is higher than 43,000 t/yr. Given the high Ag revenues, efforts should be done towards its recovery. If however a mixed silver-silicon fraction was sold for more than 50–70% of its actual value depending on the Ag concentration, a simplified process without hydrometallurgical separation could generate higher profitability on the short and long term. Given the decreasing Ag content in PVs, the profitability in recycling also depends on when the investments are realized. In the medium Ag concentration scenario and for Ag prices of 600 $/kg, PV fees are always required for the net present value (NPV) to be higher than CAPEX. The later the investment, the higher the PV throughputs and PV fees required to generate the same NPV. Investing in 2025 under the hypothesis of a regular loss scenario and an Ag price of 750 $/kg is the only condition that produces NPVs higher than CAPEX without PV fees if the throughput is at least 30,000 t/yr. • The economic sustainability in photovoltaic panel (PV) recycling is crucial. • Ag content, recycling volumes and recycling fees play crucial roles in sustainability. • A recycling fee is needed if the silver concentration in PVs is lower than 0.1%. • Earlier Investments on PV recycling projects will be more profitable. • Early investments with the current Ag price can be profitable without recycling fees.

Preparation of gelatin/Ag NPs under ultrasound condition: A potent and green bio-nanocomposite for the treatment of pleomorphic hepatocellular carcinoma, morris hepatoma, and novikoff hepatoma

Regarding applicative, facile, green chemical research, a bio-inspired approach is being reported for the sonochemical synthesis of Ag nanoparticles by gelatin as a natural reducing/stabilizing and solid support agent without using any toxic and harmful reagent. The biosynthesized Ag NPs@gelatin bionanocomposite were characterized by advanced physicochemical techniques like ultraviolet–visible (UV–Vis), Fourier Transformed Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), Energy Dispersive X-ray spectroscopy (EDX), and X-ray Diffraction (XRD) study. It has been established that gelatin-stabilized silver nanoparticles have a spherical shape with a mean diameter from ∼5–10 nm. To survey the antioxidant potentials of Ag NPs@gelatin, one of the common antioxidant techniques i.e., DPPH was used. The results of DPPH test proved excellent antioxidant properties of Ag NPs@gelatin in comparison to the positive control used i.e., butylated hydroxytoluene. The IC50 of Ag NPs@gelatin was 250 µg/mL in the antioxidant test. Determination of anti-liver cancer effects of Ag NPs@gelatin was carried out by the MTT assay and against pleomorphic hepatocellular carcinoma (SNU-387), morris hepatoma (McA-RH7777), and novikoff hepatoma (N1-S1 Fudr) cell lines. The results of MTT assay confirmed removing SNU-387, McA-RH7777, and N1-S1 Fudr cell lines after treating with low concentrations of Ag NPs@gelatin. The IC50 of the Ag NPs@gelatin was 192, 144, and 228 µg/mL against SNU-387, McA-RH7777, and N1-S1 Fudr cell lines, respectively. The best result of anti-human liver cancer effects of Ag NPs@gelatin against the above cell lines was seen in the case of the N1-S1 Fudr cell line. According to the above results, significant anti-liver cancer effects of Ag NPs@gelatin is confirmed.

Synthesis, crystal structure and electronic structure of AgxZrTe2

A systematic study of the crystal and electronic structure of the intercalation compound AgxZrTe2 in the Ag concentration range of x = 0–0.37 has been performed. It was found that the Ag atoms occupy the sites in the interlayer gap that are tetrahedrally coordinated by the Te atoms. The chemical bond is provided by the Ag 4d/Te 5p hybridization. The comparison of the studied electronic structure with the available data on the electrochemical measurements of AgxZrTe2 in the temperature range of 200–400 °C indicates the formation of covalent centers accompanied by the formation of the half-filled band of Ag 4d/Te 5p hybridized states. The shape of the phase diagram in the region of low Ag concentrations coincides with that observed for AgxTiTe2, in which the stability of the covalent centers is confirmed by the Ag 5s/Ti 3d hybridization. This indicates the universal character of the influence of the localized or extended states of conduction electrons on the phase diagram of intercalation compounds.

A facile “off–on” pattern based on one-pot synthesis of N-doped carbon dots for sensitive detection of Ag+and S2O32−

A fluorescent sensing platform based on the “off–on” mode is proposed for the detection of low concentrations of Ag+and S2O32−.

Experimental evolution of Pseudomonas putida under silver ion versus nanoparticle stress.

Whether the antibacterial properties of silver nanoparticles (AgNPs) are simply due to the release of silver ions (Ag+ ) or, additionally, nanoparticle-specific effects, is not clear. We used experimental evolution of the model environmental bacterium Pseudomonas putida to ask whether bacteria respond differently to Ag+ or AgNP treatment. We pre-evolved five cultures of strain KT2440 for 70 days without Ag to reduce confounding adaptations before dividing the fittest pre-evolved culture into five cultures each, evolving in the presence of low concentrations of Ag+ , well-defined AgNPs or Ag-free controls for a further 75 days. The mutations in the Ag+ or AgNP evolved populations displayed different patterns that were statistically significant. The non-synonymous mutations in AgNP-treated populations were mostly associated with cell surface proteins, including cytoskeletal membrane protein (FtsZ), membrane sensor and regulator (EnvZ and GacS) and periplasmic protein (PP_2758). In contrast, Ag+ treatment was selected for mutations linked to cytoplasmic proteins, including metal ion transporter (TauB) and those with metal-binding domains (ThiL and PP_2397). These results suggest the existence of AgNP-specific effects, either caused by sustained delivery of Ag+ from AgNP dissolution, more proximate delivery from cell-surface bound AgNPs, or by direct AgNP action on the cell's outer membrane.

DFT modelling of Ag doped As2S3 configurations

The generalized gradient approximation within density functional theory is used to calculate the total energies of Ag doped As2S3 configurations. The Ag is doped at octahedral, tetrahedral, c face centre and cell corner interstitial sites and As and S substitutional sites. It is found that with Ag at c face centre Ag0.25As2S3 configuration is most stable. The band structure, density of states and optical properties are investigated for this configuration. It is found that donor states are introduced below the EF in the gap region which leads to n type conductivity. The calculated values of refractive index, optical conductivity and absorption coefficient are more close to the available experimental data than those for substitutional configurations. Therefore Ag doped in As2S3 at low concentrations of Ag may occupy the c face centre interstitial site rather than any substituitional site.

Improving the Room-Temperature Ferromagnetism in ZnO and Low-Doped ZnO:Ag Films Using GLAD Sputtering.

ZnO and doped ZnO films with non-ferromagnetic metal have been widely used as biosensor elements. In these studies, the electrochemical measurements are explored, though the electrical impedance of the system. In this sense, the ferromagnetic properties of the material can be used for multifunctionalization of the sensor element using external magnetic fields during the measurements. Within this context, we investigate the room-temperature ferromagnetism in pure ZnO and Ag-doped ZnO films presenting zigzag-like columnar geometry. Specifically, we focus on the films’ structural and quasi-static magnetic properties and disclose that they evolve with the doping of low-Ag concentrations and the columnar geometry employed during the deposition. The magnetic characterization reveals ferromagnetic behavior at room temperature for all studied samples, including the pure ZnO one. By considering computational simulations, we address the origin of ferromagnetism in ZnO and Ag-doped ZnO and interpret our results in terms of the Zn vacancy dynamics, its substitution by an Ag atom in the site, and the influence of the columnar geometry on the magnetic properties of the films. Our findings bring to light an exciting way to induce/explore the room-temperature ferromagnetism of a non-ferromagnetic metal-doped semiconductor as a promising candidate for biosensor applications.

Enhancement of Mast Cell Degranulation Mediated by Purinergic Receptors' Activation and PI3K Type δ.

Mast cells express multiple metabotropic purinergic P2Y receptor (P2YR) subtypes. Few studies have evaluated their role in human mast cell (HMC) allergic response as quantified by degranulation induced by cross-linking the high-affinity IgE receptor (FcεRI). We have previously shown that extracellular nucleotides modify the FcεRI activation-dependent degranulation in HMCs derived from human lungs, but the mechanism of this action has not been fully delineated. This study was undertaken to determine the mechanism of activation of P2YRs on the degranulation of HMCs and elucidate the specific postreceptor pathways involved. Sensitized LAD2 cells, a human-derived mast cell line, were subjected to a weak allergic stimulation (WAS) using a low concentration of Ag in the absence and presence of P2YR agonists. Only the metabotropic purinergic P2Y11 receptor (P2Y11R) agonist, adenosine 5'-(3-thio)triphosphate (ATPγS), enhanced WAS-induced degranulation resulting in a net 7-fold increase in release (n = 4; p < 0.01). None of the P2YR agonists tested, including high concentrations of ATPγS (1000 μM), enhanced WAS-induced intracellular Ca2+ mobilization, an essential component of activated FcεRI-induced degranulation. Both a PI3K inhibitor and the relevant gene knockout decreased the ATPγS-induced enhancement. The effect of ATPγS was associated with enhanced phosphorylation of PI3K type δ and protein kinase B, but not the phosphoinositide-dependent kinase-1. The effects of ATPγS were dose dependently inhibited by NF157, a P2Y11R antagonist. To our knowledge, these data indicate for the first time that P2YR is linked to enhancement of allergic degranulation in HMC via the PI3K/protein kinase B pathway.

Trace Element Geochemistry of Chalcopyrites and Pyrites from Golpu and Nambonga North Porphyry Cu-Au Deposits, Wafi-Golpu Mineral District, Papua New Guinea

Studying elemental geochemistry of hypogene sulphides can discriminate the hydrothermal fluids responsible for ore formation. To determine whether Golpu porphyry Cu-Au deposits are related to the Nambonga North porphyry system which is located 2.5 km apart in the Wafi-Golpu Mineral District, Papua New Guinea, we compare the trace element compositions of drill core chalcopyrites and pyrites analysed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The results for the Golpu chalcopyrites revealed high concentrations of Au, As, Se, Mo, Sb, Te and Bi and lower concentrations of Ag and Zn compared to those from Nambonga. Pd and Pt were below the detection limit in chalcopyrites for both deposits. The results for the Golpu pyrites indicated high concentrations of Pt, Au, Se, Mo, Sb, and Te and lower concentrations of Cu, Zn, As, Ag, Pb, Pd and Bi compared to those from Nambonga North. Au concentrations in the pyrites from both the porphyry deposits were higher compared to chalcopyrites, which mean that pyrite is the Au-bearing sulphide responsible for the higher Au content. In contrast, Cu values in pyrites from Nambonga North are higher than those from Golpu. Overall, it is envisaged that the ore fluids were exsolved at different times during the evolution of both porphyry deposits, although these porphyry centres may be related in space and time.