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The Cr(VI) could be adsorbed and reduced by the humic acid (HA)-Fe(II) system structured on the V, Ti-magnetite (VTM) surface. The Cr(VI) removal process included adsorption and reduction stages. First, the Cr(VI) was adsorbed on the VTM-HA surface via the ionic bonds between the Ti atoms of VTM core and the O atoms of the HCrO4−. The adsorption of Cr(VI) is uniform, monolayer, and controlled by Cr(VI) diffusion. Subsequently, the adsorbed Cr(VI) was reduced by the HA-Fe(II) system on the VTM-HA surface. During the Cr(VI) reduction process, the HA and Fe(II) have a synergistic effect. The Cr(VI) was reduced to the Cr(III) by the HA and Fe(II). Meanwhile, the HA could also reduce Fe(III) to Fe(II), making Fe(II) continue to participate in the Cr(VI) reduction. The olefin, hydroxyl, and aldehyde groups of HA were the primary electron donors during the Cr(VI) reduction. The Fe(II) acted as an electron bridge, transferring the electron from HA to Cr(VI). The reduced Cr(III) was deposited on the VTM-HA surface via the complexation with the carboxyl and hydroxyl groups of HA. The results demonstrated that the Cr(VI) could be adsorbed, reduced and complexed by the HA-Fe(II) system on the VTM-HA surface synchronously.

HIV-1 capsid plays multiple key roles in viral replication, and inhibition of capsid assembly is an attractive target for therapeutic intervention. Here, we report the atomic-resolution structure of capsid protein (CA) tubes, determined by magic-angle spinning NMR and data-guided molecular dynamics simulations. Functionally important regions, including the NTD β-hairpin, the cyclophilin A-binding loop, residues in the hexamer central pore, and the NTD-CTD linker region, are well defined. The structure of individual CA chains, their arrangement in the pseudo-hexameric units of the tube and the inter-hexamer interfaces are consistent with those in intact capsids and substantially different from the organization in crystal structures, which feature flat hexamers. The inherent curvature in the CA tubes is controlled by conformational variability of residues in the linker region and of dimer and trimer interfaces. The present structure reveals atomic-level detail in capsid architecture and provides important guidance for the design of novel capsid inhibitors. Structures of HIV-1 capsid protein (CA) in tubular assemblies, determined by MAS-NMR, reveal the basis of CA’s conformational plasticity.

The Chinese economy is in a critical period of continuous transformation of new and old kinetic energy and economic transformation and upgrading. Copper, the second largest strategic raw material, is still central to China’s economic development. As the major producer and consumer of electrical and electronic equipment (EEE), China’s production and consumption of refined copper is the largest in the world. Thus, it is necessary to forecast the supply and demand of China’s future copper. There is a huge gap between copper production and consumption in China, the current identified copper resources cannot meet copper consumption in the next five years, thus the import of copper will be more crucial for China’s future copper industry. Due to trade frictions, restriction on imports and other reasons, the import of copper from other countries will exist a lot of uncertainties. Hence, the domestic copper waste and scraps could be the suitable secondary resource for recycling copper in China. According to the grade and value of copper scraps, establishing quality standards and optimizing the disassembly process of the domestic Cu-bearing waste & scraps, and using the suitable method are the key to recycling the domestic copper scraps.

Casein kinase 1δ (CK1δ) and casein kinase 1ε (CK1ε) have been proposed to be involved in DNA replication, differentiation and apoptosis, thus participating in the regulation of tumorigenesis. However, their functions in colon cancer and the underlying mechanism remain unclear. Here, we found that the expression of CK1ε and CK1δ increased significantly in cancer tissues and the upregulation of CK1ε and CK1δ were closely related to poor differentiation, advanced TNM stage and poor prognosis of colon cancer. CK1δ/ε inhibitor IC261 could induce a decrease in cell survival and proliferation, and an increase in apoptosis in colon cancer cells. Interestingly, IC261 increased the level of aerobic glycolysis in colon cancer cells. Meanwhile, IC261 caused the decrease of p53 protein level and the misregulation of glycolysis related genes (TIGAR, G6PD, GLUT1) which are closely related to the regulation of glycolysis by p53. Inhibiting p53 by siRNA or inhibitor could significantly attenuate the upregulation of aerobic glycolysis induced by IC261. Finally, inhibition of aerobic glycolysis can further increase the cytotoxicity induced by IC261. Collectively, our results revealed that IC261 could inhibit the growth of colon cancer cells and increase the level of aerobic glycolysis, which is regulated by p53-dependent manner. This result suggested that targeting CK1δ/ε and glycolysis might be a valuable strategy treatment and combination therapies for colon cancer.

Magnetite-type tin-bearing tailing is a typically complex secondary resource in China, of which iron and tin are with greater value. The utilization of this resource has long been a challenge due to the complex mineralogy of tin and iron minerals. In this study, the mineralogical characteristics of the tailings were studied. It was found that tin mainly existed as fine-grained cassiterite and lattice Sn4+ (Fe3-xSnxO4) in magnetite particles, which was almost impossible to recover by physical mineral processing. Fe2.6Sn0.4O4 samples were synthesized to study the mineral phase reconstructions of Fe3-xSnxO4 under CO−CO2 atmosphere, as well as in the presence of Na2CO3 or CaO. Then, three proposed processes of selective reduction roasting, sodium roasting and calcium roasting processes were demonstrated and applied in the separation of tin and iron. Finally, some suggestions were recommended for the separation of tin from magnetite-type tin-bearing tailings. Keywords: Fe3-xSnxO4, Cassiterite, Separation, Selective reduction roasting, Sodium roasting, Calcium roasting

Some basic research has shown that nanomaterials can aggravate allergic asthma. However, its potential mechanism is insufficient. Based on the research that alumina nanopowder (nAl2O3) has been reported to cause lung tissue damage, the purpose of this study was to explore the relationship between nAl2O3 and allergic asthma as well as its molecular mechanism. In this study, Balb/c mice were sensitized with ovalbumin (OVA) to construct the allergic asthma model while intratracheally administered 0.5, 5 or 50 mg kg−1·day−1 nAl2O3 for 3 weeks. It was observed that exposure to nAl2O3 exacerbated airway hyperresponsiveness (AHR), airway remodeling, and inflammation cell infiltration, leading to lung function damage in mice. Results revealed that nAl2O3 could increase ROS levels and decrease GSH levels in lung tissue, promote the increases of the T-IgE, TGF-β, IL-1β and IL-6 levels, stimulate the overexpression of transcription factors GATA-3 and RORγt, decrease the levels of IFN-γ and IL-10 and increase the levels of IL-4 and IL-17A, resulting in the imbalance of Th1/Th2 and Treg/Th17 immune responses. In addition, antioxidant Vitamin E (Vit E) could alleviate asthma-like symptoms through blocking oxidative stress. The study displayed that exposure of nAl2O3 deteriorated allergic asthma through promoting the imbalances of Th1/Th2 and Treg/Th17.

We report remarkably high, up to 100-fold, signal enhancements in (19)F dynamic nuclear polarization (DNP) magic angle spinning (MAS) spectra at 14.1 T on HIV-1 CA capsid protein assemblies. These enhancements correspond to absolute sensitivity ratios of 12–29 and are of similar magnitude as seen for (1)H signals in the same samples. At MAS frequencies above 20 kHz, it was possible to record 2D (19)F-(13)C HETCOR spectra, which contain long-range intra- and intermolecular correlations. Such correlations provide unique distance restraints, inaccessible in conventional experiments without DNP for protein structure determination. Furthermore, systematic quantification of the DNP enhancements as a function of biradical concentration, MAS frequency, temperature, and microwave power is reported. Our work establishes the power of DNP-enhanced (19)F MAS NMR spectroscopy for structural characterization of HIV-1 CA assemblies and this approach is anticipated to be applicable to a wide range of large biomolecular systems.

Lead (Pb) ions are chronically detected in soil, underground and natural water, there is a need for low-cost in situ remediation techniques. A novel mineral based magnetic adsorbent, consisting of natural vanadium, titanium-bearing magnetite particles coated by humic acid (abbr. VTM-HA), was developed for removing Pb(II) from wastewater. In this study, adsorption-desorption characteristics and mechanisms of Pb (II) on the VTM-HA adsorbent were investigated. The regeneration and reuse feasibility of the VTM-HA adsorbent were also conducted. The adsorption tests further verified that Pb(II) was removed rapidly and efficiently by the VTM-HA adsorbent. Moreover, Pb (II) adsorbed on the VTM-HA adsorbent could be easily eluted using a small amount of acidic eluent, and the desorption of Pb (II) could reach 99.3 wt% in 0.1 M HNO3 (pH = 1). After five adsorption-desorption regeneration cycles, the magnetism and Pb(II) adsorption capacity of the regenerated VTM-HA adsorbent almost kept unchanged. The results indicated that the VTM-HA adsorbent had excellent adsorption capacity and regenerative ability, which could be used as ideal adsorbents for removing Pb (II) from acid wastewater in commercial application. The mechanisms of Pb (II) adsorption and desorption were explored by FTIR, XPS analysis and DFT calculation.

Despite the advantages of colorimetric detection methods, their application to glucose detection in fruit and vegetable samples has been limited by interference from other matrix components. Herein, a colorimetric sensor for hydrogen peroxide and glucose detection was developed based on an enzymatic-like reaction that induced the iodine-mediated etching of gold nanoparticles (AuNPs). The AuNPs were fabricated using a MoO3-nanosheet-assisted photochemical process without any surface modification or purification steps. Furthermore, the MoO3 nanosheet residues and Mo(VI) ions leached during AuNP preparation acted directly as peroxidase-like catalysts to promote the reduction of iodate to iodine in the presence of hydrogen peroxide (or the glucose–glucose oxidase enzymatic system). The generated iodine then etched the AuNPs, resulting in an obvious colour change of the reaction solution that allowed the selective and quantitative spectrophotometric determination of hydrogen peroxide and glucose. The linear ranges for the detection of hydrogen peroxide and glucose were 40–380 μM (R2 = 0.99) and 100–1000 μM (R2 = 0.98), respectively, with detection limits of 0.55 μM and 0.45 μM, respectively. The developed colorimetric method was applied to the determination of glucose in water chestnuts with good recoveries (100–108%), demonstrating its applicability to glucose detection in fruits.

There are abundant ferruginous manganese ores (abbr. Fe-Mn ores) in many parts of the world. For example, almost half of the manganese ore resources in India are ferruginous and more than 73% of the manganese ores in China belong to Fe-Mn ores with a low Mn/Fe mass ratio ( Numerous approaches are reported to realize the selective extraction and separation of Mn and Fe from the Fe-Mn ores. The extraction and separation technologies cover physical beneficiation, chemical beneficiation (hydrometallurgy and pyrometallurgy) and physico-chemical combined processes. This present work reviews the technical principles, parameters and recovery efficiencies of diverse processes on the aspect of selective extraction and separation of Mn and Fe from Fe-Mn ores. This review can provide guidance for selecting appropriate methods to exploit Fe-Mn ores or other secondary resources containing Fe and Mn oxides. The authors also put forward a new route to produce manganese ferrite materials using Fe-Mn ores as the raw materials.

Due to its excellent properties such as ultraviolet obscuration, chemical stability and small particle size, nano-titanium dioxide (nano-TiO2) is widely used, particularly in sunblock products. The skin is therefore a chief route for exposure. Studies have found that oral or respiratory exposure to nano-TiO2 has an adverse impact on the cardiovascular system. The relationship between dermal exposure to nano-TiO2 and cardiovascular system toxicity, particularly the causative mechanisms, remain unclear. In this study, we used Balb/c mice to evaluate cardiovascular toxicity from nano-TiO2 dermal exposure, and the underlying mechanisms associated with the human umbilical vein endothelial cells (HUVECs) were explored. Our results showed that nano-TiO2 treatment resulted in an obvious increase in reactive oxygen species and 8-hydroxy-2'-deoxyguanosine, indicating the appearance of oxidative stress. Moreover, the levels of inflammatory biomarkers, such as immunoglobulin E, soluble intercellular adhesion molecule-1, interleukin-8, and hypersensitive C-reactive protein, also increased. Exposing HUVECs to nano-TiO2 led to a decline in cell vitality, and an increase in caspase-3 levels, suggesting that nano-TiO2 exposure caused cytotoxicity and even cell apoptosis. Interestingly, neutralizing oxidative stress by administering Vitamin E was shown to reduce the inflammatory response and cytotoxicity. Our findings suggest that nano-TiO2 can injure the cardiovascular system via dermal exposure, and does this via oxidative stress-induced inflammation and cytotoxicity. Vitamin E treatment may be a strategy to mitigate the damage.

In this study, high pure humic acid (HA) extracted from lignite was fractionated into four fractions according to their molecular weights by the ultrafiltration method. The structural characteristics of various HA fractions were investigated by UV–Vis,FTIR, and 3D fluorescence spectra and 13C/1H-NMR tests. The experiment results showed that the HA fractions with the molecular weight ＞50 KDa are major, containing 70.89%. The active hydrogen proportion declined from 43.96% to 21.27% with the increase of HA molecular weight, meaning the decrease of the large HA molecules’ acidic group content. On the other hand, 80.93% of the aromatic nucleus content and 12.5% of the alkyl carbon (aliphatic structure) were observed in the large HA molecules that are much higher than those in the small HA molecules. The NMR and spectra studies indicated that the small HA molecules have more acidic groups such as hydroxy, carboxyl. Meanwhile, the large HA molecules have more aromatic and aliphatic structures. The above research indicated that the HA fractions with low molecular weight could provide more active sites for the interaction between HA and iron minerals. Moreover, the carbon chain and aromatic nucleus in the high molecular weight HA fractions could keep the space structure of HA stable.

The Fe3O4 and Fe2SiO4 in copper slag were successfully reduced to metallic iron by coal-based direct reduction. Under the best reduction conditions of 1300 &deg, C reduction temperature, 30 min reduction time, 35 wt.% coal dosage, and 20 wt.% CaO dosage (0.75 binary basicity), the Fe grade of obtained iron concentration achieved 91.55%, and the Fe recovery was 98.13%. The kinetic studies on reduction indicated that the reduction of copper slag was controlled by the interfacial reaction and carbon gasification at 1050 &deg, C. When at a higher reduction temperature, the copper slag reduction was controlled by the diffusion of the gas. The integral kinetics model research illustrated that the reaction activation energy increased as the reduction of copper slag proceeded. The early reduction of Fe3O4 needed a low reaction activation energy. The subsequent reduction of Fe2SiO4 needed higher reaction activation energy compared with that of Fe3O4 reduction.

Pyrite cinder is a typical hazardous waste produced from sulfuric acid industry, which always contains a significant level of valuable metals. About 12 million tons of pyrite cinder are generated in China annually, and the utilization rate is less than 50% due to the complex relationship of various components. In this study, a process of acid leaching was used to separate and recover copper from the pyrite cinder (containing 0.60 wt.% Cu and 56.01 wt.% Fe). Both sulfuric acid and phosphoric acid systems were taken into consideration, and the effect of leaching parameters on the recovery of copper was conducted to investigate the effect of selective leaching in the two acidic systems. The results indicated that the recovery of copper in sulfuric or phosphoric acid system was as high as 89.6 wt.% and 82.3 wt.%, respectively. It was found that part of copper in pyrite cinder closely combined with silicon, which was impossible to separate during the acid leaching process.

Pb(II) is a typical toxin in industrial wastewater, which has significant pollution risk for drinking water sources. Magnetic manganese ferrites are a proven recyclable adsorption material on account of their excellent ferromagnetism. In this study, manganese ferrites adsorbent synthesized from ferromanganese ore were used for Pb(II) removal from acid wastewater. Thermodynamic calculation and adsorption tests were conducted. Under optimal conditions, the removal ratio of Pb(II) reached 99.4% when initial Pb(II) concentration was 10 mg/L (pH = 5), and the residual Pb(II) concentration was reduced to lower than 0.1 mg/L. The results indicated that the synthetic manganese ferrites were an excellent magnetic adsorbent, which was easy to be separated and recycled. The adsorption mechanism was explored by isothermal adsorption analysis using φ-pH and ICP.

Bentonite is the most common binder for the vanadium, titanium-bearing magnetite (VTM) pellet production. However, inorganic bentonite will reduce the iron grade of the finished products because ab...

19 F NMR spectroscopy is an attractive and growing area of research with broad applications in biochemistry, chemical biology, medicinal chemistry, and materials science. We have explored fast magic angle spinning (MAS) 19 F solid-state NMR spectroscopy in assemblies of HIV-1 capsid protein. Tryptophan residues with fluorine substitution at the 5-position of the indole ring were used as the reporters. The 19 F chemical shifts for the five tryptophan residues are distinct, reflecting differences in their local environment. Spin-diffusion and radio-frequency-driven-recoupling experiments were performed at MAS frequencies of 35 kHz and 40-60 kHz, respectively. Fast MAS frequencies of 40-60 kHz are essential for consistently establishing 19 F-19 F correlations, yielding interatomic distances of the order of 20 A. Our results demonstrate the potential of fast MAS 19 F NMR spectroscopy for structural analysis in large biological assemblies.

Carbonization of pure MnO2 by CH4-H2 gas mixture with various CH4/(CH4 + H2) molar ratios in the temperature range of 900–1250 °C had been performed in our previous work. This study further investigated the carbonization and alloying process of MnO2 by CH4-H2 gas mixture in the presence of Fe2O3 at 900–1300 °C using XRD, optical microstructure, SEM-EDS and phase diagram analyses. Carbonization test of pure Fe2O3 was also conducted to understand the effect of Fe2O3 on the carbonization of MnO2 more explicitly. It was found that Fe2O3 could be carbonized to Fe3C at 900–1150 °C. The Fe2O3 briquettes began to melt at 1100 °C and a large amount of Fe-C melts appeared as the temperature went up to 1150 °C. When the MnO2 + 25 wt%Fe2O3 briquettes were reduced at 900–1000 °C in CH4-H2 gas mixture, the Fe2O3 was preferentially carbonized to Fe-C phase while the MnO2 was only reduced to MnO. The formation of Fe-C phase was beneficial to the carbonization of MnO since the carbonization temperature of MnO can decrease from 1100 °C to 1000 °C. The carbonization degree of MnO was dramatically accelerated over 1100 °C due to the transformation of Fe-C phase from solid state to melts. Morphology analysis indicated that the MnO core was wrapped by the shell of Fe-C melts. The alloying process of Mn-Fe-C was conducted through the elements migration of Fe and Mn between the core and shell. At 1300 °C, the Mn-Fe-C alloy turned to melt and aggregated since the highest melting temperature of the Mn-C-25 wt% Fe system was only 1274 °C. Finally, a ferromanganese crude alloy with 68–72 wt% Mn, 20–25 wt% Fe and 6.0–8.0 wt% C was obtained when the MnO2 + 25 wt% Fe2O3 briquettes were carbonized by CH4-H2 gas mixture at 1300 °C for 60 min.

Methionine restriction (MR) has been reported to have many beneficial health effects, including stress resistance enhancement and lifespan extension. However, the effects of MR on the splenic metabolic dysfunction induced by obesity in mice remain unknown. This study aimed to investigate the scientific problem and clarify its possible mechanisms. C57BL/6J mice in the control group were fed a control diet (0.86% methionine, 4.2% fat) for 34 weeks, and others were fed a high-fat diet (0.86% methionine, 24% fat) for 10 weeks to establish diet-induced obese (DIO) mouse models. Then, the obtained DIO mice were randomly divided into two groups: the DIO group (DIO diet), the DIO + MR group (0.17% methionine, 24% fat) for 24 weeks. Our results indicated that MR decreased spleen weight, and spleen and plasma lipid profiles, promoted lipid catabolism and fatty acid oxidation, glycolysis and tricarboxylic acid cycle metabolism, and improved mitochondrial function and ATP generation in the spleen. Moreover, MR normalized the splenic redox state and inflammation-related metabolite levels, and increased plasma levels of immunoglobulins. Furthermore, MR increased percent lean mass and splenic crude protein levels, activated the autophagy pathway and elevated nucleotide synthesis to maintain protein synthesis in the spleen. These findings indicate that MR can ameliorate metabolic dysfunction by reducing lipid accumulation, oxidative stress, and inflammation in the spleen, and the mechanism may be the activation of autophagy pathway.

Part of tin in the magnetite-type tin-bearing ores existed as isomorphous Sn4+ in the lattice of magnetite (Fe3-xSnxO4, X = 0–1.0), which was impossible to separate and recover by physical beneficiation methods In this study, a calcified roasting process under CO-CO2 atmosphere was applied to separate tin from the magnetite-type tin-bearing tailings, and the results indicated that the isomorphous Sn4+ in the magnetite was removed effectively. Then, Fe2.6Sn0.4O4 was synthesized to investigate the interface reaction mechanisms between CaO and Fe3-xSnxO4. The results indicated that the calcified roasting process can be divided into three stages: the ionic migration of Sn4+ on the interface between CaO and Fe3-xSnxO4 and formation of calcium stannates (Ca2SnO4/CaSnO3), diffusion of Sn4+ through the product layer (CaSnO4/Ca2SnO4), the oxidation of FeO to Fe3O4 by CO2. These findings can provide theoretical support for the utilization of magnetite-type tin-bearing tailings by the calcified roasting process.

The proven global tin reserves were reported to be approximately 4.7 million tons (Mts) in 2016, and among these resources, only approximately 2.2 Mts can be recovered economically. The original tin deposits will be exhausted in several years, therefore, tin-bearing secondary resources, such as tin alloy, tin anode slime, e-wastes, tin slag and tin-bearing tailings, will become the primary source from which tin can be extracted. Many investigations have been conducted on the recovery of tin from these tin-bearing materials. However, the separation and recovery approaches of tin vary significantly, since the content and phase compositions of tin are totally different in these secondary resources. This paper reviews these methods of extracting and separating tin from different kinds of tin-bearing secondary resources.

Single particle cryoEM has emerged as a powerful method for structure determination of proteins and complexes, complementing X-ray crystallography and NMR spectroscopy. Yet, for many systems, the resolution of cryoEM density map has been limited to 4-6 Å, which only allows for resolving bulky amino acids side chains, thus hindering accurate model building from the density map. On the other hand, experimental chemical shifts (CS) from solution and solid state MAS NMR spectra provide atomic level data for each amino acid within a molecule or a complex; however, structure determination of large complexes and assemblies based on NMR data alone remains challenging. Here, we present a novel integrated strategy to combine the highly complementary experimental data from cryoEM and NMR computationally by molecular dynamics simulations to derive an atomistic model, which is not attainable by either approach alone. We use the HIV-1 capsid protein (CA) C-terminal domain as well as the large capsid assembly to demonstrate the feasibility of this approach, termed NMR CS-biased cryoEM structure refinement.

Sodium stannate (Na2SnO3) has been successfully prepared by a novel process of roasting cassiterite concentrates and sodium carbonate (Na2CO3) under CO&ndash, CO2 atmosphere, namely soda roasting-leaching process. However, more than 22 wt. % tin of the cassiterite was not converted into Na2SnO3 and entered the leach residues. Quartz (SiO2) is the predominant gangue in the cassiterite, and phase evolution of SnO2&ndash, SiO2&ndash, Na2CO3 system roasted under CO&ndash, CO2 atmosphere was still uncertain. In this study, the effect of SiO2 in cassiterite concentrates on preparation of Na2SnO3 was clarified. The results indicated that Na8SnSi6O18 was inevitably formed when cassiterite and Na2CO3 were roasted above 775 &deg, C under CO&ndash, CO2 atmosphere via the reaction of SnO2 + 6SiO2 + 4Na2CO3 = Na8SnSi6O18 + 4CO2, and formation of Na8SnSi6O18 would be increased with increasing roasting temperature and Si/Sn mole fraction. In addition, it was found that Na8SnSi6O18 was insoluble in the leachate at pH value range of 1&ndash, 14, which, therefore, was enriched in the leach residues. The silicon content of the cassiterite concentrates should be controlled as lower as possible to obtain a higher conversion ratio of Na2SnO3.

We present (19)F longitudinal and transverse relaxation studies for four differently fluorosubstituted l-tryptophans, which carry single F atoms in the indole ring, both in the context of the free amino acid and when located in the cyclophilin A protein. For the free 4F-, 5F-, 6F-, 7F-l-Trp, satisfactory agreement between experimentally measured and calculated relaxation rates was obtained, suggesting that the parameters used for calculating the rates for the indole frame are sufficiently accurate. We also measured and calculated relaxation rates for four differently (19)F-tryptophan labeled cyclophilin A proteins, transferring the parameters from the free amino acid to the protein-bound moiety. Our results suggest that (19)F relaxation data of the large and rigid indole ring in Trp are only moderately affected by protein motions and provide critical reference points for evaluating fluorine NMR relaxation in the future, especially in fluorotryptophan labeled proteins.

Pyrite cinder is a typical hazardous waste produced in sulfuric acid industry, which, however, contains a significant level of valuable metals, such as iron, copper, cobalt, etc. About 12 million tons of pyrite cinder are generated in China annually, while the utilization rate is less than 50% due to the complex relationship of various components. In this study, a process of phosphoric acid leaching was used to selectively separate and recover Cu, Co and Fe from the pyrite cinder. The effects of different leaching parameters on the recovery rate of valuable metals in phosphoric acid leaching systems were investigated. Under the optimal conditions, the results indicated that the leaching efficiency of copper and cobalt was above 82% and 99%, respectively. More than 98% of iron was transferred into insoluble FePO4·2H2O, which could be used as precursor of battery-grade electrode material after a hydrofluoric acid purification process. Cu and Co in the leaching solutions were extracted efficiently by P204.

Acid wastewater containing toxic metal ions has become increasingly important global environmental concern and lead (Pb) is one of the prime toxic heavy metal ions. Humic acid (HA), a kind of natural organic matter, has been proven to have a great adsorption capacity for metal cations (Pb2+, Cu2+, etc.). Our previous study has verified that HA has excellent adsorbing ability on vanadium titanium-bearing magnetite(VTM) particles. In this study, VTM-HA complex magnetic particles were prepared for removing Pb(II) from acid wastewater, which could be easily recycled by magnetic separation. The effects of pH value, ionic strength and VTM-HA concentration on the removal ratio of Pb(II) were determined by isothermal adsorption tests. The results indicated that Pb(II) adsorption was subject to pH and ionic strength. When initial Pb(II) concentration is 100 mg/L, the residual concentration and removal ratio of Pb(II) reach 0.17 mg/L and 99.83%, respectively, which are much lower than the discharge standard.

The negative global impact of the AIDS pandemic is well known. In this perspective article, the utility of magic angle spinning (MAS) NMR spectroscopy to answer pressing questions related to the structure and dynamics of HIV-1 protein assemblies is examined. In the recent years, MAS NMR has undergone major technological developments enabling studies of large viral assemblies. We discuss some of these evolving methods and technologies and provide a perspective on the current state of MAS NMR as applied to the investigations into structure and dynamics of HIV-1 assemblies of CA capsid protein and of Gag maturation intermediates.

International audience; The recent breakthroughs in NMR probe technologies resulted in the development of MAS NMR probes with rotation frequencies exceeding 100 kHz. Herein, we explore dramatic increases in sensitivity and resolution observed at MAS frequencies of 110-111 kHz in a novel 0.7 mm HCND probe that enable structural analysis of fully protonated biological systems. Proton- detected 2D and 3D correlation spectroscopy under such conditions requires only 0.1-0.5 mg of sample and a fraction of time compared to conventional 13C-detected experiments. We discuss the performance of several proton- and heteronuclear- (13C-,15N-) based correlation experiments in terms of sensitivity and resolution, using a model microcrystalline fMLF tripeptide. We demonstrate the applications of ultrafast MAS to a large, fully protonated protein assembly of the 231-residue HIV-1 CA capsid protein. Resonance assignments of protons and heteronuclei, as well as 1H-15N dipolar and 1HN CSA tensors are readily obtained from the high sensitivity and resolution proton-detected 3D experiments. The approach demonstrated here is expected to enable the determination of atomic-resolution structures of large protein assemblies, inaccessible by current methodologies.

International audience; Mature infectious HIV-1 virions contain conical capsids composed of CA protein, generated by the proteolytic cleavage cascade of the Gag polyprotein, termed maturation. The mechanism of capsid core formation through the maturation process remains poorly understood. We present DNP-enhanced MAS NMR studies of tubular assemblies of CA and Gag CA-SP1 maturation intermediate and report 20-64-fold sensitivity enhancements due to DNP at 14.1 T. These sensitivity enhancements enabled direct observation of spacer peptide 1 (SP1) resonances in CA-SP1 by dipolar-based correlation experiments, unequivocally indicating that the SP1 peptide is unstructured in assembled CA-SP1 at cryogenic temperatures, corroborating our earlier results. Furthermore, the dependence of DNP enhancements and spectral resolution on magnetic field strength (9.4-18.8 T) and temperature (109-180 K) was investigated. Our results suggest that DNP-based measurements could potentially provide residue-specific dynamics information by allowing for the extraction of the temperature dependence of the anisotropic tensorial or relaxation parameters. With DNP, we were able to detect multiple well-resolved isoleucine side-chain conformers; unique intermolecular correlations across two CA molecules; and functionally relevant conformationally disordered states such as the 14-residue SP1 peptide, none of which are visible at ambient temperatures. The detection of isolated conformers and intermolecular correlations can provide crucial constraints for structure determination of these assemblies. Overall, our results establish DNP-based MAS NMR spectroscopy as an excellent tool for the characterization of HIV-1 assemblies.

In this study, a comparative study of adsorption characteristics of humic acid (HA) onto Ca-montmorillonite and Na-montmorillonite were carried out to guide the preparation of a novel composite binder for iron ore pellets, namely humic acid modified bentonite (HAMB). Using Ca-montmorillonite (Ca Mt) as a representative, the adsorption mechanisms of HA onto montmorillonite were studied by XRD, zeta potential, FTIR and XPS analyses. The results indicated that HA was adsorbed onto Ca Mt mainly via complexation and H-bonds. The DFT calculation and molecular dynamics simulation were also carried out to further determine the adsorption mechanisms of HA onto Ca Mt. Molecular dynamics simulation analyses showed that the complexation reaction between carboxyl, hydroxyl groups of HA and Ca ions in Ca Mt is dominant in HA adsorption. And the pelletizing experiments indicated that the HAMB binder prepared at a pH value of 7 had excellent application effect in iron ore pelletization.

HIV-1 CA capsid protein possesses intrinsic conformational flexibility, which is essential for its assembly into conical capsids and interactions with host factors. CA is dynamic in the assembled capsid, and residues in functionally important regions of the protein undergo motions spanning many decades of time scales. Chemical shift anisotropy (CSA) tensors, recorded in magic-angle-spinning NMR experiments, provide direct residue-specific probes of motions on nano- to microsecond time scales. We combined NMR, MD, and density-functional-theory calculations, to gain quantitative understanding of internal backbone dynamics in CA assemblies, and we found that the dynamically averaged 15N CSA tensors calculated by this joined protocol are in remarkable agreement with experiment. Thus, quantitative atomic-level understanding of the relationships between CSA tensors, local backbone structure, and motions in CA assemblies is achieved, demonstrating the power of integrating NMR experimental data and theory for cha...

Experimental characterization of one-bond heteronuclear dipolar couplings is essential for structural and dynamics characterization of molecules by solid-state NMR. Accurate measurement of heteronuclear dipolar tensor parameters in magic-angle spinning NMR requires that the recoupling sequences efficiently reintroduce the desired heteronuclear dipolar coupling term, fully suppress other interactions (such as chemical shift anisotropy and homonuclear dipolar couplings), and be insensitive to experimental imperfections, such as radio frequency (rf) field mismatch. In this study, we demonstrate that the introduction of window delays into the basic elements of a phase-alternating R-symmetry (PARS) sequence results in a greatly improved protocol, termed windowed PARS (wPARS), which yields clean dipolar lineshapes that are unaffected by other spin interactions and are largely insensitive to experimental imperfections. Higher dipolar scaling factors can be attained in this technique with respect to PARS, which is particularly useful for the measurement of relatively small dipolar couplings. The advantages of wPARS are verified experimentally on model molecules N-acetyl-valine (NAV) and a tripeptide Met-Leu-Phe (MLF). The incorporation of wPARS into 3D heteronuclear or homonuclear correlation experiments permits accurate site-specific determination of dipolar tensors in proteins, as demonstrated on dynein light chain 8 (LC8). Through 3D wPARS recoupling based spectroscopy we have determined both backbone and side chain dipolar tensors in LC8 in a residue-resolved manner. We discuss these in the context of conformational dynamics of LC8. We have addressed the effect of paramagnetic relaxant Cu(ii)-EDTA doping on the dipolar coupling parameters in LC8 and observed no significant differences with respect to the neat sample permitting fast data collection. Our results indicate that wPARS is advantageous with respect to the windowless version of the sequence and is applicable to a broad range of systems including but not limited to biomolecules.

Soybean saponin has a lot of physiological activities and pharmacological action and has been extensively used in health food and medicine. In this paper, an adsorption chromatographic method with a resin column was developed to obtain crude soybean saponins. After that, a silica column was used to separate crude soybean saponins and prepare group B soybean saponins which consist of soybean saponin I, II, III, IV and V. During the process of extraction and separation of soybean saponins, ultraviolet spectrometry (UV), thin layer chromatography (TLC) and high performance liquid chromatography-mass spectrometry (HPLC-MS) were employed to monitor and identify soybean saponins. The result shows that the developed method can be used to prepare group B soybean saponins.