50,820 research outputs found
Nitric oxide inhibits cruzipain, the major papain-like cysteine proteinase from Trypanosoma cruzi
No full textNitric oxide (NO) is a pluripotent regulatory molecule showing, among others, an antiparasitic activity. Moreover, NO inhibits cysteine proteinase action by nitrosylating the Cys catalytic residue. In the present study, the inhibitory effect of the substrate N-α-benzyloxycarbonyl-L-phenylalanyl-L-arginine-(7-amino-4-methylcoumarin) and of NO on the catalytic activity of cruzipain, the major papain-like cysteine proteinase from Trypanosoma cruzi (the hemoflagellate protozoan parasite which causes the American trypanosomiasis), is reported. In particular, NO-donors S-nitroso-glutathione (GSNO), (±)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (NOR-3), 3-morpholinosydnonimine (SIN-1), S-nitroso-acetyl-penicillamine (SNAP), and sodium nitroprusside (SNP) dose-dependently inhibited cruzipain, this effect being likely attributable to the S-nitrosylation of the Cys25 catalytic residue. These results were analyzed in parallel with those concerning the inhibitory effect of the substrate and of NO on the catalytic activity of falcipain, the cruzipain-homologous cysteine proteinase from Plasmodium falciparum. The modulation of the cruzipain and falcipain activity by NO may be relevant in developing new strategies against T. cruzi and P. falciparum in human host. As a whole, the NO-mediated S-nitrosylation of pathogenic viral, bacterial, fungal, and parasitic cysteine proteinases may represent a general mechanism of antimicrobial and antiparasitic host defences. (C) 2000 Academic Press
Nitric oxide inhibits cruzipain, the major papain-like cysteine protease from Trypanosoma cruzi
No full textWettability of HfB2 by molten Ni(B) alloys interpreted by CALPHAD methods, Part 1: Definition of the B–Hf–Ni system
No full textA monitoring of an automatic control system used in an innovative fermenter during red wine vinification
No full textZirconia-High Entropy Alloys joints for biomedical applications: the role of Ag-based fillers on interfacial reactivity
No full textMetal-ceramic joints represent an important choice for biomedical devices, in orthopaedic field or as micro-stimulators. ZrO2-Ag-HEA joint is here proposed to replace the currently used Ti6Al4V by new Ti-based refractory HEAs. To evaluate the system reactivity, wettability of ZrO2 by different Ag-based alloys at 1000 degrees C and their interfacial layers were studied, for the first time. Interpretation and discussion of systems reactivity were supported by thermodynamic calculations, according to the CALPHAD approach and the ad-hoc Ag-Ti-Zr-O thermodynamic database, implemented in this work. A good wettability was reached at 1000 degrees C adding Ti to Ag: Ag-4Ti and Ag-8Ti reached contact angles of 81-85 degrees. Ag-4Ti-2Zr showed the best wettability (77 degrees) and the most complex interfacial microstructure. A continuous hcp (Ti,O), similar to 20 mu m thick, promoted the wettability of Ag-4Ti and Ag-8Ti. In both cases, AgTi was the only intermetallic compound found in the bulk. Ag-4Ti-2Zr formed a thicker interfacial layer of hcp-(Ti,Zr,O) + bcc-(Ti,Zr) + a less compact Ag(Ti,Zr)(2) layer. Here, a low amount of Ag(Ti,Zr) and Ag(Ti,Zr)(2) was found in the Ag matrix. Since Ag resulted a promising filler to braze Ti-rich substrates to ZrO2 at 1000 degrees C, preliminary HEA-Ag-ZrO2 joints were characterized. A sound and defects-free interface was observed, with a first layer, mainly formed by Ag, Ti and Zr (HV similar to 600), and a Ag-based interface (HV similar to 250), extending until the HEA. Further works envisage mechanical and electrochemical evaluations of the system to pave the way for the production of novel HEA-Ag-ZrO2 joints to be used in biomedical applications. (C) 2022 Published by Elsevier B.V
Wettability of SiC and graphite by Co–Ta alloys: evaluation of the reactivity supported by thermodynamic calculations
No full textWithin the context of the design of high-temperature brazing process for C and SiC-based composites, a basic study is presented here about the wetting and interfacial reactivity of CoâTa alloys in contact with graphite or SiC. Wetting results are presented for the first time showing that CoâTa alloys wet C or SiC fairly or excellently depending on the relative amount of Ta. The final interfacial microchemistry and microstructures are the result of the interplay between the typical interfacial phenomena of the pure elements. Specifically, depending on the alloy composition, dissolution of the ceramic phase by Co or formation of a continuous interfacial layer of TaC that prevents dissolution prevails. The discussion about the interfacial reactivity between liquid CoâTa alloys and graphite or SiC, as well as the interpretation of solidification phenomena and the formation of interfacial phases, is supported by making reference to new multi-component phase diagrams calculated by CALPHAD method
Monitoraggio di un sistema di controllo automatico usato in un innovativo vinificatore ad asse orizzontale con cappello sommerso e gabbia rotante
No full textBrazing transparent YAG to Ti6Al4V: Reactivity and characterization
No full textThe YAG/filler/Ti6Al4V system has been studied for the first time with the aim of producing brazed optical windows. Different fillers (AgCuTi, AgCu, Ag) and temperatures have been taken into account and the interfacial zones of the samples have been evaluated in terms of morphology and compositions. A thin and continuous metal-ceramic layer containing Ti is formed in contact with the YAG ensuring the adhesion between all the joined materials. The best joining results have been obtained at 850. °C, where we have observed the formation of an interfacial CuTi layer when AgCuTi and Ag have been used. No intermetallic compound formation was observed using the pure Ag at 970. °C and 1050. °C. The phase formation was interpreted using the CALPHAD method by means of recalculated Ag-Cu-Ti and Ag-Al-Ti isothermal sections. Microhardness tests have been conducted to evaluate the performances of the joints in terms of mechanical properties
Diamond–metal interfaces in cutting tools: a review
No full textThis paper reviews studies undertaken on diamond cutting tools, with particular regard to the characteristics and performance of diamond/metal interfaces. The affinity of carbon to metals, as well as the wettability of diamond by molten metals and the advantage of using coated diamonds under certain cutting conditions, are described. The choice of the appropriate metallic matrix in the field of both impregnated and brazed diamond tools, is discussed in terms of the diamond/alloy interface, mechanical properties of the segment, diamond wear speed and desired cutting performance. The effect of several principal elements and elements added in minor amounts to the metallic matrix is critically evaluated. Relevant open questions, related to the optimization of cutting tools performance, are outlined, with special attention directed towards the need for advanced fundamental studies on the functional link between Work of Adhesion and Work of Fracture
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