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Effect of water content and storage conditions on the activity of carbon fiber supported palladium-copper-iron containing catalyst was studied. Physical-chemical properties of catalytic system were examined by means of XRD, XPS, SEM and GCh. The optimal water content in the catalyst, which ensures the most effective air purification both at low (0,03 vol.%) and high (0,5 vol.%) CO concentrations in the air and high humidity (70 %) of gas mixture, was determined.Activity loss of the catalytic system after storage under air conditions (1 month) was attributed to the accumulation of the excess amount of water in the catalyst and reorganization of its the active phase – decrease in the palladium content in the near-surface layer and segregation of the Сu2Cl(OH)3 atacamite phase. Catalyst drying in air at 110 оС leads to its complete reactivation. Hermetically sealed freshly as-prepared and dried at 50 оС after experiment samples retain the initial catalytic activity during long-term (more than a year) storage.

Here, we have examined the nanoporous activated carbon fibers (ACFs) sulfonated using the direct sulfonation and the staged method that included bromination, followed by sulfidation and oxidation. TEM confirmed the nanoporous structure of the prepared sulfonated ACFs. Nitrogen porometry and 2D nonlocal DFT simulations showed the nanoporosity reduction and variations of the pore size distribution because of the functionalization. Comparison of parameters of the SO3H groups confined in nanopores, e.g., the thermal stability and catalytic potential, showed that the most efficient acid sites, in the catalytic 2-propanol dehydration to propylene, are the SO3H groups grafted by the staged Houben–Weil methods. From the productivity of reactions used at the preparation stage, and in contrast to the one-staged aromatic substitution, the bromine addition to π sites of the edges of carbon matrix supplies enough active sites and is a reason for further high yields of the grafted thermostable SO3H groups. Hydrolysis of the grafted bromine and the surface oxidation of nanopores walls are parallel reactions that lowered the SO3H-related acidity, increasing the total acidity to 1.5 mmol g−1. The reported nanoporous sulfonated ACFs are effective to be used in the dehydration reactions catalyzed by solid acids.

The process of thermal activation of a carbon fiber supported with palladium-copper-iron-containing catalysts has been studied by means of DSC and TGA in air and in nitrogen. The presence of the exoeffect during calcination due to the interaction of the copper (II) nitrate decomposition products with the carbon carrier was detected. Aforementioned exoeffect leads to spontaneous heating and combustion of the sample in air. The XPS and catalytic experiments showed that calcination of the catalyst in nitrogen leads to the formation of low-activity reaction centers. Oxygen plays an important role in the formation of the active phase, so the thermal activation of catalyst should be carried out in the air.

The influence exerted by the conditions of oxidation and calcination in an inert medium on the properties of Karbopon and Busofit activated carbon fibers were studied using a set of physicochemical methods. The maximal concentration of thermally stable phenol groups in Busofit is reached by its oxidation with a 20% aqueous HNO3 solution, followed by calcination in an inert medium at 500°С for 1.5 h. Experiments with catalysts supported on Busofit samples functionalized with 20% HNO3 have shown that palladium supported on Busofit that was calcined at 500°C after oxidative treatment is characterized by monodisperse nanocluster distribution. The prepared catalysts containing 1 wt % Pd exhibit higher activity in oxidation of carbon monoxide than their presently known analogs do.

We studied the effects of the composition of impregnating solution and heat treatment conditions on the activity of catalytic systems for the low-temperature oxidation of CO obtained by the impregnation of Busofit carbon-fiber cloth with aqueous solutions of palladium, copper, and iron salts. The formation of an active phase in the synthesized catalysts at different stages of their preparation was examined with the use of differential thermal and thermogravimetric analyses, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and elemental spectral analysis. The catalytic system prepared by the impregnation of electrochemically treated Busofit with the solutions of PdCl2, FeCl3, CuBr2, and Cu(NO3)2 and activated under optimum conditions ensured 100% CO conversion under a respiratory regime at both low (0.03%) and high (0.5%) carbon monoxide contents of air. It was found that the activation of a catalytic system at elevated temperatures (170–180°C) leads to the conversion of Pd(II) into Pd(I), which was predominantly localized in a near-surface layer. The promoting action of copper nitrate consists in the formation of a crystalline phase of the rhombic atacamite Cu2Cl(OH)3. The catalyst surface is finally formed under the conditions of a catalytic reaction, when a joint Pd(I)-Cu(I) active site is formed.

The endoplasmic reticulum (ER) is the largest intracellular endomembrane system, enabling protein and lipid synthesis, ion homeostasis, quality control of newly synthesized proteins and organelle communication(1). Constant ER turnover and modulation is needed to meet different cellular requirements and autophagy has an important role in this process(2-8). However, its underlying regulatory mechanisms remain unexplained. Here we show that members of the FAM134 reticulon protein family are ER-resident receptors that bind to autophagy modifiers LC3 and GABARAP, and facilitate ER degradation by autophagy ('ER-phagy'). Downregulation of FAM134B protein in human cells causes an expansion of the ER, while FAM134B overexpression results in ER fragmentation and lysosomal degradation. Mutant FAM134B proteins that cause sensory neuropathy in humans(9) are unable to act as ER-phagy receptors. Consistently, disruption of Fam134b in mice causes expansion of the ER, inhibits ER turnover, sensitizes cells to stress-induced apoptotic cell death and leads to degeneration of sensory neurons. Therefore, selective ER-phagy via FAM134 proteins is indispensable for mammalian cell homeostasis and controls ER morphology and turnover in mice and humans.

The immunity-related GTPases (IRGs) constitute an interferon-induced intracellular resistance mechanism in mice against Toxoplasma gondii. IRG proteins accumulate on the parasitophorous vacuole membrane (PVM), leading to its disruption and to death of the parasite. How IRGs target the PVM is unknown. We show that accumulation of IRGs on the PVM begins minutes after parasite invasion and increases for about 1 h. Targeting occurs independently of several signalling pathways and the microtubule network, suggesting that IRG transport is diffusion-driven. The intensity of IRG accumulation on the PVM, however, is reduced in absence of the autophagy regulator, Atg5. In wild-type cells IRG proteins accumulate cooperatively on PVMs in a definite order reflecting a temporal hierarchy, with Irgb6 and Irgb10 apparently acting as pioneers. Loading of IRG proteins onto the vacuoles of virulent Toxoplasma strains is attenuated and the two pioneer IRGs are the most affected. The polymorphic rhoptry kinases, ROP16, ROP18 and the catalytically inactive proteins, ROP5A-D, are not individually responsible for this effect. Thus IRG proteins protect mice against avirulent strains of Toxoplasma but fail against virulent strains. The complex cooperative behaviour of IRG proteins in resisting Toxoplasma may hint at undiscovered complexity also in virulence mechanisms.

Summary The immunity-related GTPases (IRGs) constitute an interferon-induced intracellular resistance mechanism in mice against Toxoplasma gondii. IRG proteins accumulate on the parasitophorous vacuole membrane (PVM), leading to its disruption and to death of the parasite. How IRGs target the PVM is unknown. We show that accumulation of IRGs on the PVM begins minutes after parasite invasion and increases for about 1 h. Targeting occurs independently of several signalling path- ways and the microtubule network, suggesting that IRG transport is diffusion-driven. The intensity of IRG accumulation on the PVM, however, is reduced in absence of the autophagy regulator, Atg5. In wild-type cells IRG proteins accumulate cooperatively on PVMs in a definite order reflecting a temporal hierarchy, with Irgb6 and Irgb10 appar- ently acting as pioneers. Loading of IRG proteins onto the vacuoles of virulent Toxoplasma strains is attenuated and the two pioneer IRGs are the most affected. The polymorphic rhoptry kinases, ROP16, ROP18 and the catalytically inactive proteins, ROP5A-D, are not individually responsible for this effect. Thus IRG proteins protect mice against avirulent strains of Toxoplasma but fail against virulent strains. The complex cooperative behav- iour of IRG proteins in resisting Toxoplasma may hint at undiscovered complexity also in virulence mechanisms.

A number of platinum-based catalysts bonded on carbon fiber karbopon were prepared using alcohol solutions of H2PtCl6. The catalytic activity of the samples was determined in the low-temperature oxidation of carbon monoxide by oxygen. The effect of the solvent nature of the precursor on the activity of the catalysts was determined. The best results were obtained in the presence of 1.5% Pt/karbopon catalyst prepared using isobutyl alcohol; 100% CO conversion was achieved in respiratory treatment (12000 h−1, room temperature).

A number of supported-metal (Pt, Pd) catalysts based on Karbopon nonwoven carbon fibers were prepared by deposition from hydrosols and by ion exchange. The catalytic activity of the catalysts in low-temperature oxidation of carbon monoxide by atmospheric oxygen was determined. Catalyst samples were studied by transmission electron microscopy.

Catalytic systems containing palladium, copper, and iron compounds on carbon supports-kernel activated carbon and fibrous carbon materials (Karbopon and Busofit)-for the low-temperature oxidation of CO were synthesized. The effects of the nature of the support, the concentration and composition of the active component, and the conditions of preparation on the efficiency of the catalytic system were studied. The catalytic system based on Karbopon exhibited the highest activity: the conversion of carbon monoxide was 90% at room temperature and a reaction mixture (0.03% CO in air) space velocity of 10 000 h. It was found that the metals occurred in oxidized states in the course of operation: palladium mainly occurred as Pd, whereas copper and iron occurred as Cu and Fe, respectively. © 2008 MAIK Nauka.

Selective autophagy regulates the abundance of specific cellular components via a specialized arsenal of factors, termed autophagy receptors, that target protein complexes, aggregates, and whole organelles into lysosomes. Autophagy receptors bind to LC3/GABARAP proteins on phagophore and autophagosome membranes, and recognize signals on cargoes to deliver them to autophagy. Ubiquitin (Ub), a well-known signal for the degradation of polypeptides in the proteasome, also plays an important role in the recognition of cargoes destined for selective autophagy. In addition, a variety of cargoes are committed to selective autophagy pathways by Ub-independent mechanisms employing protein-protein interaction motifs, Ub-like modifiers, and sugar- or lipid-based signals. In this article we summarize Ub-dependent and independent selective autophagy pathways, and discuss regulatory mechanisms and challenges for future studies.

Measurement of protease activity in living cells or organisms remains a challenging task. We here present a transgene-encoded biosensor that reports the proteolytic activity of caspase-1 in the course of inflammasome activation and that of other proteases in a highly sensitive and specific manner. This protease reporter is based on the biological activity of a pro-interleukin (IL)-1β-Gaussia luciferase (iGLuc) fusion construct, in which pro-IL-1β-dependent formation of protein aggregates renders GLuc enzyme inactive. Cleavage leads to monomerization of this biosensor protein, resulting in a strong gain in luciferase activity. Exchange of the canonical caspase-1 cleavage site in this reporter construct allows the generation of protease biosensors with additional specificities. The high sensitivity, signal-to-background ratio and specificity of the iGLuc system renders it a useful tool to study proteolytic events in mouse and human cells at high throughput and to monitor protease activity in mice in vivo.

Background The interferon-inducible immunity-related GTPases (IRG proteins/p47 GTPases) are a distinctive family of GTPases that function as powerful cell-autonomous resistance factors. The IRG protein, Irga6 (IIGP1), participates in the disruption of the vacuolar membrane surrounding the intracellular parasite, Toxoplasma gondii, through which it communicates with its cellular hosts. Some aspects of the protein's behaviour have suggested a dynamin-like molecular mode of action, in that the energy released by GTP hydrolysis is transduced into mechanical work that results in deformation and ultimately rupture of the vacuolar membrane. Results Irga6 forms GTP-dependent oligomers in vitro and thereby activates hydrolysis of the GTP substrate. In this study we define the catalytic G-domain interface by mutagenesis and present a structural model, of how GTP hydrolysis is activated in Irga6 complexes, based on the substrate-twinning reaction mechanism of the signal recognition particle (SRP) and its receptor (SRα). In conformity with this model, we show that the bound nucleotide is part of the catalytic interface and that the 3'hydroxyl of the GTP ribose bound to each subunit is essential for trans-activation of hydrolysis of the GTP bound to the other subunit. We show that both positive and negative regulatory interactions between IRG proteins occur via the catalytic interface. Furthermore, mutations that disrupt the catalytic interface also prevent Irga6 from accumulating on the parasitophorous vacuole membrane of T. gondii, showing that GTP-dependent Irga6 activation is an essential component of the resistance mechanism. Conclusions The catalytic interface of Irga6 defined in the present experiments can probably be used as a paradigm for the nucleotide-dependent interactions of all members of the large family of IRG GTPases, both activating and regulatory. Understanding the activation mechanism of Irga6 will help to explain the mechanism by which IRG proteins exercise their resistance function. We find no support from sequence or G-domain structure for the idea that IRG proteins and the SRP GTPases have a common phylogenetic origin. It therefore seems probable, if surprising, that the substrate-assisted catalytic mechanism has been independently evolved in the two protein families.

Toxoplasma gondii is a widespread protozoan parasite infecting all warm-blooded animals and causing disease in immunocompromised individuals and in utero. The pathogen depends on the intracellular life style residing in a specialized organelle, termed parasitophorous vacuole (PV), in order to survive and replicate. Cell-autonomous immunity, regulated by IFNg, is essential to restrict growth of the parasite in mouse and man. In mouse cells, resistance to T. gondii is mediated by the family of IFN-inducible IRG proteins (p47 GTPases). Upon infection several IRG proteins associate with the PV and participate in vesiculation of the PV membrane leading to demise of the parasite and necrotic death of the cell. Until now, despite intrinsic interest, the phenomenon of IRG protein loading onto PV has not been well studied. In human cells, depletion of cellular tryptophan by IDO has been reported as the major mechanism of restriction of T. gondii proliferation exerted by IFNg. IDO-independent restriction of T. gondii growth has been reported but not followed up. The process of IRG protein association with T. gondii vacuoles emerged as a rapid, organized and diffusion-driven event where multiple resistance proteins sequentially bind to the vacuolar membrane forming homomeric and heteromeric complexes. The efficient loading process requires the autophagy factor Atg5 regulating correct localisation of IRG proteins prior to infection. Virulent strains of T. gondii inhibit IRG protein association with PVs independently of individual virulence determinants ROP5, ROP16 and ROP18. Impaired loading of IRG proteins onto T. gondii vacuoles leads to reduced elimination of the parasite in IFNg-stimulated cells, underlining the importance of the phenomenon in cell-autonomous immunity to T. gondii. This study shows that density of cultured cells is the key factor in determining the mode of T. gondii control in primary human cells. IFNg-induced, proliferating cells control parasite replication independently of IDO. Consistent with absence of the IRG system in humans, the vacuolar membrane and enclosed parasite remain intact in IFNg-induced human cells. However, similar to mouse cells, human cells die by necrosis, when infected with T. gondii and stimulated with IFNg. This may not only suppress parasite growth but also amplify an antimicrobial response due to release of the proinflammatory �danger� signal HMGB1. Programmed necrosis could be efficiently suppressed at high densities of primary cells and in HeLa cell line, and tryptophan depletion becomes the main source of T. gondii control.

The immunity related GTPases (IRG proteins) constitute a large family of interferon-inducible proteins that mediate early resistance to Toxoplasma gondii infection in mice. At least six members of this family are required for resistance of mice to virulent T. gondii strains. Recent results have shown that the complexity of the resistance arises from complex regulatory interactions between different family members. The mode of action against T. gondii depends on the ability of IRG proteins to accumulate on the parasitophorous vacuole of invading tachyzoites and to induce local damage to the vacuole resulting in disruption of the vacuolar membrane. Virulent strains of T. gondii overcome the IRG resistance system, probably by interfering with the loading of IRG proteins onto the parasitophorous vacuole membrane. It may be assumed that T. gondii strains highly virulent for mice will be disadvantaged in the wild due to the rapid extinction of the infected host, while it is self-evident that susceptibility to virulent strains is disadvantageous to the mouse host. We consider the possibility that this double disadvantage is compensated in wild populations by segregating alleles with different resistance and susceptibility properties in the IRG system.

Toxoplasma gondii is a natural intracellular protozoal pathogen of mice and other small mammals. After infection, the parasite replicates freely in many cell types (tachyzoite stage) before undergoing a phase transition and encysting in brain and muscle (bradyzoite stage). In the mouse, early immune resistance to the tachyzoite stage is mediated by the family of interferon-inducible immunity-related GTPases (IRG proteins), but little is known of the nature of this resistance. We reported earlier that IRG proteins accumulate on intracellular vacuoles containing the pathogen, and that the vacuolar membrane subsequently ruptures. In this report, live-cell imaging microscopy has been used to follow this process and its consequences in real time. We show that the rupture of the vacuole is inevitably followed by death of the intracellular parasite, shown by its permeability to cytosolic protein markers. Death of the parasite is followed by the death of the infected cell. The death of the cell has features of pyronecrosis, including membrane permeabilisation and release of the inflammatory protein, HMGB1, but caspase-1 cleavage is not detected. This sequence of events occurs on a large scale only following infection of IFNγ-induced cells with an avirulent strain of T. gondii, and is reduced by expression of a dominant negative mutant IRG protein. Cells infected by virulent strains rarely undergo necrosis. We did not find autophagy to play any role in the key steps leading to the death of the parasite. We conclude that IRG proteins resist infection by avirulent T. gondii by a novel mechanism involving disruption of the vacuolar membrane, which in turn ultimately leads to the necrotic death of the infected cell., Author Summary Toxoplasma gondii infects many warm-blooded animals, including approximately one quarter of the world's human population, residing life-long, usually asymptomatically, in cysts in the brain. If, however, the immune system is weakened for any reason, T. gondii can break out and cause life-threatening disease. Furthermore, early T. gondii infection can transfer to the fetus and cause damage. Yet, the human is not a natural host for this parasite. T. gondii reproduces sexually only in cats and the life cycle depends on carnivory by cats of infected intermediate hosts, normally small mammals like the mouse. If the mouse cannot slow down the infection by immune resistance, T. gondii can be lethal. We show that a family of intracellular mouse proteins called immunity-related GTPases (IRGs) can attack T. gondii early after it has infected a cell and kill at least some of the parasites. The infected cells die too, but we show that in dying they release a protein that can stimulate local immunity. For most strains of T. gondii, this early immune attack is probably enough to prevent the parasite from killing the mouse, and allows the parasite to establish a long-lasting infection in the mouse brain or muscle.