179 research outputs found
Chelation of copper(II) by daunomycin and 5-iminodaunomycin and interaction of the complexes with mononucleotides: An ESR study
No full textCoordination of copper(II) ions by daunomycin and 5-iminodaunomycin has been studied by electron spin resonance spectroscopy, at various values of pH and r, the anthracycline-to-Cu(II) molar ratio. At r = 1–5, polymeric complexes are formed in the case of daunomycin. At r = 5, a mononuclear complex is predominant and at r = 10, this is the only one formed with the 63Cu and 65Cu hyperfine interaction being clearly defined in the g∥ region (g∥ = 2.26, 63A∥ = 175; 65A∥ = 190 G). For 5-iminodaunomycin both chelation sites are involved in the coordination and a polymeric structure (in which exchange interactions between Cu(II) centers operate) is stable in the range r = 1–3. At r = 3, the triplet state of a dinuclear Cu(II) complex is observed and 5-iminodaunomycin behaves as both a bridging and a terminal ligand. For r = 5–10, the dinuclear complex coexists with the mononuclear one. In the presence of mononucleotides dGMP, dAMP, dCMP and thymidine, no ternary complex such as mononucleotide/Cu(II)/anthracycline was observed
Antioxidant activity of polyphenols from solid olive residues of c.v. Coratina
No full textThe antioxidant profile of extracts from solid olive residue (SOR) of c.v. Coratina, a cultivar widely diffused in the south of Italy, using both cell-free and cell-based experimental models, was investigated. A total hydroalcoholic extract (polyphenols content 19.7%) and a purified extract (Oleaselect (TM)) (polyphenols content 35.1%) were tested for their ability to quench the stable free radical DPPH, the peroxyl radicals (ORAC assay), by monitoring the loss in fluorescence of R-phycoerythrin induced by the peroxyl radical generator AAPH and their ability to inhibit the cumene hydroperoxide-induced lysis of rat red blood cells (RBC). The total hydroalcoholic extract showed IC50 26.96 +/- 1.53 mu g/ml in the DPPH assay, that 10 mu g/ml were equivalent to 2.11 +/- 0.12 mu g/ml Trolox (ORAC assay) and IC50 1.7 +/- 0.20 mu g/ml in the RBC hemolysis. The Oleaselect (TM) extract was 4 to 5 folds more active than the hydroalcoholic extract in all the experimental models, with IC50 values of 7.36 +/- 0.38 mu g/ml in the DPPH test and of 0.38 +/- 0.03 mu g/ml in RBC; the antioxidant activity in the ORAC assay was slightly greater than that of Trolox (10 mu g/ml equivalent to 11.45 +/- 0.40 mu g/ml). The scavenging effect of the extract in the ORAC assay was compared to that of verbascoside (the main polyphenol component) and of caffeic acid (the basic constituent of verbascoside): the results indicate that caffeic acid (10 mu g/ml equivalent to 35.70 +/- 2.95 mu g/ml Trolox) is more potent than verbascoside (10 mu g/ml equivalent to 15.42 +/- 1.21 mu g/ml Trolox) in entrapping peroxyl radicals. Finally the antioxidant activity of the Oleaselect (TM) extract was confirmed in human umbilical endothelial cells (EC) exposed to the site-specific peroxyl radical inducer AAPH, where a massive lipid peroxidation process (marker the fluorescence probe BODIPY) takes place, paralleled by a marked loss of cell viability (calcein assay). The purified extract (1-20 mu g/ml) pre-incubated with EC for 1 h dose-dependently inhibited both the lipid-peroxidation damage and cell death. Taking into account the total polyphenol content, these results clearly indicate a greater antioxidant activity for the purified extract, due to a cooperative antioxidant interaction among its polyphenol constituent
Paramagnetic metal species on highly dispersed Rhodium/Polyphosphine catalysts
No full textESR active paramagnetic species were used as a probe for the description of the metal centers in highly dispersed rhodium/polyphosphine catalysts. Magnetically dilute Rh(0) centers were observed at high P Rhs] (s = surface) ratios. Two different Rh(d0) diluted species were detected (g1 = 2.085, g2 = 2.000; g′1 = 2.045, g′2 = 2.008, g′3 = 1.975) whose relative amounts vary with the P Rhs value. At lower P Rhs values, metal crystallites play a dominant role in giving broad unresolved signals. The metal particle size and the absolute Rh% are also related to the resonance shape. It is suggested that phosphine coordinates Rh centers, where a rhombic species corresponds to a higher number of coordinated phosphines. The results of the ESR investigation are in good agreement with previous studies on the same catalysts (G. Cocco, S. Enzo, F. Pina, and G. Strukul, J. Catal. 82, 160, 1983) performed by SAXS, WAXS, TGA, TPR, and infrared study of CO adsorption
ON THE USE OF ELECTRON-SPIN-RESONANCE IN INVESTIGATING DISPERSED METAL SYSTEMS - A CONTRIBUTION TO RELATIONSHIPS BETWEEN CLUSTERS AND METAL-SURFACES
No full textProcyanidines from Vitis vinifera seeds protect rabbit heart from ischemia reperfusion injury: Antioxidant intervention and/or iron and copper sequestering ability
No full textAn isolated rabbit heart Langendorff preparation paced electrically was used to evaluate the effects of a highly purified, high molecular weight fraction of oligomeric procyanidines isolated from Vitis vinifera seeds on myocardial reperfusion injury after 40 minutes of low flow (1 ml/min) ischemia. Infusion of the heart with 100 or 200 mu g/ml procyanidines dose-dependently reduced ventricular contracture during ischemia (LVEDP values decreased by 28% and 51%), decreased coronary perfusion pressure (CPP), improved cardiac mechanical performance upon reperfusion, increased the release of 6-keto-PGF(1 alpha) into the perfusate in both the pre-ischemic and the reperfusion periods (by 68% at 200 mu g/ml), and suppressed rhythm irregularity. This antiarrhythmogenic action was confirmed in a more severe model of ischemia (flow rate 0.2 ml/min). The cardioprotective agent allopurinol infused at 20 mu g/ml had effects on the contractility and on the release of 6-keto-PGF(1 alpha) comparable to those of 200 mu g/ml procyanidines. The results of the second part of this study show that procyanidines are potent scavengers of several reactive oxygen species involved in the ischemia/reperfusion damage: the superoxide anion (IC50 = 5.64 mu M; rate constant K = 7.55 x 10(5) M(-1) s(-1), determined by the phenazine methosulfate/NADH method); the hydroxyl radical (IC50 = 28 mu M; rate constant K = 1.2 x 10(12) M(-1) s(-1), determined by the electron spin resonance spectroscopy); peroxyl radicals (IC50 = 0.025 mu M and 0.35 mu M, determined using two different lipid substrates, phosphatidylcholine liposomes and methyl linoleate micelles by UV spectroscopy at 233 nm). Finally, procyanidines interact with Fe2+ and Cu2+ ions (the catalysts of HO. radicals production) giving rise to strong complexes, with stability constants (log K) ranging from 9.35 to approximate to 9
Social media, percorsi e narrazioni: una geografia digitale del turismo naturalistico
No full textIl turismo, soprattutto quello di massa, può avere un impatto negativo sull’ambiente e sulle culture locali. Al fine di superare questa criticità negli ultimi anni si sono moltiplicate le proposte di forme di turismo alternativo. Tra queste il turismo naturalistico offre delle interessanti opportunità, oggi accentuate dalla diffusione dei social media e da piattaforme digitali realizzate per aiutare e incentivare gli utenti propensi ad esplorare gli ambienti naturali.
In questo lavoro, oltre a descrivere le più comuni dinamiche e criticità riguardanti il turismo naturalistico, si approfondisce il caso della piattaforma digitale AllTrails.Social media, routes and narrations: a digital geography of nature-based tourism. Tourism, especially mass tourism, can have a negative impact on the environment and local cultures. In order to overcome this criticality, the proposals for alternative forms of tourism have multiplied in recent years. Nature-based tourism offers interesting opportunities, today enriched by the diffusion of social media and digital platforms created to help and encourage users who desire to explore natural environments. In this work, in addition to describing the most common dynamics and critical issues concerning nature-based tourism, the case of the AllTrails digital platform is explored
Oxygen chemisorption on γ-Al2O3·phthalocyaninato·-cobalt(II): Coordination of O2 by complexed cobalt centers; Tumbling of molecular oxygen on surface cobalt centers
No full textThe system phthalocyaninatocobalt(II)·Al2O3, ([Co(pc)]·γ-Al2O3), if contacted with air at high temperatures (70 - 150 °C), has been found to be active to oxygen chemisorption. ESR measurements revealed that the chemisorption is a reversible process, leading to the formation of [Co(pc)O2]·γ-Al2O3 as a paramagnetic intermediate. ESR spectroscopy has also been used to investigate the rate of angular reorientation of O2 absorbed on the [Co(pc)]·γ-Al2O3 surface at a variety of temperatures. Computer simulations of the ESR spectra were compared with spectra obtained experimentally, and correlation times for reorientation and anisotropic g values were calculated. The fitting of the anisotropic g values to a model based on second-order perturbation theory suggests that the ground state of [Co(pc)O2]·γ-Al2O3 is (x2 - y2)2(z2)2(xz or yz)2(yz or xz), with the unpaired electron localized mainly on cobalt. According to this finding, oxygen interacts with cobalt mainly through a π overlap. © 1982
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