Pursuing the Complete OFF State in Photoswitchable Catalysis

Practically, all photoswitchable catalysts exhibit residual activity in the OFF state. Herein, we present a ruthenium initiator with a built-in photoswitch whose metathetical performance is completely shut off by light. The system is made of Hoveyda−Grubbs second-generation complexes appended, along with background ligands, to a gold nanoparticle surface via azobenzene linkers. Under dark or visible light - the precatalysts, in the presence of an olefin, undergo initiation, diffuse from the surface into bulk solution, and commence metathesis reaction. When the conditions are changed to ultraviolet, the isomerization of the azo switches takes place, burying the precatalysts within the bulky organic monolayer, thus preventing their initiation and thereby halting the reaction. Despite the irreversibility of the process, this work opens up opportunities for the remote deactivation of catalysts without their chemical decomposition and control of more complex tasks such as chemical selectivity

Glutathione peroxidase and hydroperoxides: designing in silico approaches to case-studies

reservedThe mechanism of the oxidative step of glutathione peroxidases (GPx) has been well elucidated in silico and implies a long-range proton transfer mediated by a peroxide and a water molecule, followed by a nucleophilic attack to the peroxide O-O bond by the catalytic chalcogenolate. In this Thesis, we have revisited this enzymatic stage setting up a protocol to include dynamic effects of the protein environment and using a particular substrate, i.e. peroxynitrite, which might turn the activity of the endogenous peroxidatic system into a harmful hydrogen peroxide source.The mechanism of the oxidative step of glutathione peroxidases (GPx) has been well elucidated in silico and implies a long-range proton transfer mediated by a peroxide and a water molecule, followed by a nucleophilic attack to the peroxide O-O bond by the catalytic chalcogenolate. In this Thesis, we have revisited this enzymatic stage setting up a protocol to include dynamic effects of the protein environment and using a particular substrate, i.e. peroxynitrite, which might turn the activity of the endogenous peroxidatic system into a harmful hydrogen peroxide source

Techno-economic feasibility of anaerobic digestion of cheese whey in small Italian dairies and effect of ultrasound pre-treatment on methane yield

In Friuli-Venezia Giulia plain (North-East of Italy), a significant number of small diaries is present; this study was aimed at evaluating technical and economic feasibility of diffused anaerobic digestion implementation at dairy level. Different kinds of cheese whey were characterized, and biochemical methane potential tests were executed. Good methane yields (up to 437.3 NmL CH4/g VSadded) were obtained, applying an inoculum-to-substrate ratio of 6. Ultrasound pre-treatment was investigated to evaluate an eventual increase in methane production and kinetics, varying applied ultrasonic energy: significant increases in methane yield (maximum +16.0%) and CH4 production kinetics (up to +46% increase after 3 days) were obtained at low ultrasonic energy of 251.4-693.7\ua0Wh/kg VS, while at higher ultrasonic energy of 502.8-1387.5\ua0Wh/kg VS no significant effect was visible. Energy consumption in selected dairies was analysed, to underline the impact of anaerobic digestion implementation on electric and thermal energy need, and it was concluded that through cheese whey anaerobic digestion it is possible to cover most of the dairies energy demand. Specific electric and thermal energy consumption were evaluated to be respectively in the range of 0.009-0.133\ua0kWh/kg milk and 0.247-0.557\ua0MJ/kg milk, while specific energy costs were calculated as 0.0079-0.0308 \u20ac/kg milk. For each analysed plant, digester volume to install and organic loading rate were hypothesized

398 Rifaximin Displays a Protective Activity in Experimental Enteropathy Induced by Indomethacin in Rats

Introduction. Nonsteroidal anti-inflammatory drugs, besides exerting detrimental effects on the upper digestive tract, can also damage the small and large intestine. Although the underlying mechanisms remain unclear, there is evidence that enteric bacteria play a pivotal role. On this basis, the present study examined the entero-protective effects of rifaximin, a poorly absorbed antibiotic with a broad spectrum of antibacterial activity, in a rat model of indomethacin (IND)-induced enteropathy. Methods. Enteropathy was induced in 40-weekold male rats by intragastric (i.g.) IND administration (1.5 mg/kg BID) for 14 days. A delayed-release formulation of rifaximin (REIR, 50 mg/kg BID, i.g.) was administered 1 hour before IND. Subgroups of rats treated with IND or REIR+IND also received omeprazole (OME, 0.7 mg/kg OD, i.g.), as inhibitor of gastric acid secretion. At the end of treatments, blood samples were collected to evaluate hemoglobin (Hb) concentration (as an index of digestive bleeding). Small intestine was excised and processed for: 1) histological assessment of intestinal damage (percentage length of lesions over the total length examined); 2) assay of tissue myeloperoxidase (MPO) levels, as an index of neutrophil infiltration; 3) assay of tissue malondialdehyde (MDA) concentration, as an index of lipid peroxidation. Results. Rats treated with IND displayed a 13.3% mortality rate, while in groups treated with REIR+IND or OME+IND the mortality rate was lower (8.3% and 6.7%, respectively). No deaths were observed in controls or animals treated with OME+REIR+IND. IND treatment significantly decreased Hb levels (by 28%). While OME did not affect the Hb decrease, it was significantly lessened in rats treated with REIR+IND or OME+REIR+IND. IND treatment was associated with the occurrence of lesions in the jejunum and ileum. In both intestinal regions of rats treated with REIR+IND or OME+REIR+IND the percentage of lesions was significantly lower, as compared with rats receiving IND alone. The severity of lesions elicited by IND was reduced by co-treatment with OME in the jejunum, but not in the ileum. MPO and MDA levels in jejunum and ileum from IND-treated rats were significantly increased, as compared with controls. While OME was unable to affect these parameters, in rats treated with REIR+IND or OME+REIR+IND, MPO and MDA levels were not significantly different from those observed in controls. Results obtained are summarized in the enclosed Table. Conclusion. REIR treatment significantly prevents IND-induced intestinal damage, this entero-protective effect being associated with a decrease in tissue inflammation, oxidative stress and digestive bleeding. Administration of OME does not appear to affect the parameters related to intestinal damage, with few minor exceptions

Small bowel protection against NSAID-injury in rats: Effect of rifaximin, a poorly absorbed, GI targeted, antibiotic

Nonsteroidal anti-inflammatory drugs, besides exerting detrimental effects on the upper digestive tract, can also damage the small and large intestine. Although the underlying mechanisms remain unclear, there is evidence that enteric bacteria play a pivotal role. The present study examined the enteroprotective effects of a delayed-release formulation of rifaximin-EIR (R-EIR, 50mg/kg BID, i.g.), a poorly absorbed antibiotic with a broad spectrum of antibacterial activity, in a rat model of enteropathy induced by indomethacin (IND, 1.5mg/kg BID for 14 days) administration. R-EIR was administered starting 7 days before or in concomitance with IND administration. At the end of treatments, blood samples were collected to evaluate hemoglobin (Hb) concentration (as an index of digestive bleeding). Small intestine was processed for: (1) histological assessment of intestinal damage (percentage length of lesions over the total length examined); (2) assay of tissue myeloperoxidase (MPO) and TNF levels, as markers of inflammation; (3) assay of tissue malondialdehyde (MDA) and protein carbonyl concentrations, as an index of lipid and protein peroxidation, respectively; (4) evaluation of the major bacterial phyla. IND significantly decreased Hb levels, this effect being significantly blunted by R-EIR. IND also induced the occurrence of lesions in the jejunum and ileum. In both intestinal regions, R-EIR significantly reduced the percentage of lesions, as compared with rats receiving IND alone. Either the markers of inflammation and tissue peroxidation were significantly increased in jejunum and ileum from IND-treated rats. However, in rats treated with R-EIR, these parameters were not significantly different from those observed in controls. R-EIR was also able to counterbalance the increase in Proteobacteria and Firmicutes abundance induced by INDO. To summarize, R-EIR treatment significantly prevents IND-induced intestinal damage, this enteroprotective effect being associated with a decrease in tissue inflammation, oxidative stress and digestive bleeding as well as reversal of NSAID-induced alterations in bacterial population