Search results for "Reaction"

Immunohistochemical and transcriptional expression of matrix metalloproteinases in full-term human umbilical cord and Human Umbilical Vein Endothelia…

2010

Matrix metalloproteinases (MMPs) are extracellular zinc-dependent endopeptidases involved in the degradation and remodelling of extracellular matrix in physiological and pathological processes. MMPs also have a role on cell proliferation, migration, differentiation, angiogenesis and apoptosis. Umbilical cord is a special organ subjected to many changes during pre-natal life and whose cells can maintain a certain degree of plasticity also in post-natal period; for example recently they have been used as a source of stem cells. In this work we investigated the expression of MMPs in human umbilical cord and Human Umbilical Vein Endothelial Cells (HUVEC) though immunohistochemistry, RT-PCR and …

Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS) for the study of the aromatic potential of bakery starter strains

2016

The influence of substitution in the quinoxaline nucleus on 1,3-dipolar cycloaddition reactions

2013

The reaction mechanism of 1,3-dipolar cycloadditions of both symmetric and unsymmetric benzo-condensed diazines with a nitrilimine dipole, to give two different mono- and bis-cycloadducts, in tetrahydrofuran (THF) solution, was studied by DFT calculatio ns. The results obtained show that each 1,3-dipolar cycloaddition reaction always proceeds by a two steps mechanism, in which the first intermediate shows only one covalent bond between the beta carbon of the nitrilimine and the aromatic nitrogen of the diazine molecule. The structure and energy content of the two transition states of the two cycloaddition steps, in the case of the unsymmetric benzo-condensed diazine, nicely explains why the…

Sunlight-induced functionalisation reactions of heteroaromatic bases with aldehydes in the presence of TiO2: A hypothesis on the mechanism

2007

In previous studies we reported a new photocatalytic system involving polycrystalline TiO2 for the selective functionalisation of heteroaromatic bases with ethers and amides. In order to extend the applications of this new reaction and to better understand the mechanism involved, we have examined aromatic and aliphatic aldehydes as acyl radical sources for the nucleophilic addition to protonated N-heteroarenes in acetonitrile as the solvent and TiO2/H2O2 as the photocatalytic system. Acyl radicals may undergo decarbonylation to yield the corresponding alkyl radicals. Acyl/alkyl derivative ratios depend on the nature of the aldehydes, and present a different distribution from that obtained i…

LIQUIDI IONICI E FULLERENI: PIATTAFORME PER NUOVI MATERIALI

The synthesis of innovative catalysts based on different carbon nanoforms (CNFs), namely fullerene C60 and carbon nanotubes (CNTs), and their application in Suzuki and Heck C-C coupling reactions, constitutes the common thread of the first part (Chapter 1 and 2) of this thesis. C60 and CNTs were functionalized with ionic liquids (ILs) and poly-amidoamine (PAMAM) dendrimers, respectively, and used as supports for palladium nanoparticles (PdNPs). Moreover, additional supported catalytic systems based on one of the synthesized C60-IL hybrids were prepared and successfully employed in the title coupling reactions. The final part (Chapter 3) of the thesis deals on the microwave-mediated synthesi…

ASYMMETRIC SYNTHESIS OF LINEZOLID THROUGH CATALYZED HENRY REACTION

2013

Linezolid 1 is an antibacterial oxazolidinone approved by FDA in 2000 for the treatment of fastidious bacterial infections.1 The asymmetric synthesis of Linezolid-like molecules make use of the chiral pool approach, through the so-called Manninen reaction.2 This strategy requires the use of BuLi, low temperature and a long elaboration of the acetamide chain. Curiously, the only catalyzed approach toward the asymmetrical synthesis of Linezolid was just recently reported, and belongs to the use of proline-derived catalysts in aldol reactions as the key step.3 This procedure is quite interesting except for the low yield. Here we report a new synthesis of Linezolid, based on a Cu(II)-catalyzed …

Lipase-catalyzed resolution of anti-substituted 1,3-dioxepan-5-ols

2006

Several anti-6-substituted 1,3-dioxepan-5-ols were kinetically resolved using an immobilized lipase (Amano PS–C II) in toluene in the presence of vinyl acetate at 30 C. This approach provided, in some cases, the alcohol and the acetate in high enantiomeric purity, depending on the nature of the substituent (R = N3, SePh, I, OBn) and the acetal group (unsubstituted or dimethyl). The role of the size of substituents is also discussed. Enantiopure anti-6-substituted 1,3-dioxepan-5-ols are useful building blocks.

Nanostructured Ni-Co Alloy Electrodes Fabrication and Characterization for both Hydrogen and Oxygen Evolution Reaction in Alkaline Electrolyzer

2019

Sun and wind as power sources are becoming more and more relevant owing to the progressive abandoning of the fossil fuels [1,2]. Additionally, worldwide public authorities are encouraging the use of renewable energies by promoting laws and guidelines [3,4]. In this scenario, a fundamental role can play hydrogen that besides being a valuable energy carrier, it can also act as a storage medium to balance the discontinuity affecting the renewable energy sources production [5]. As a consequence, cheap and abundant availability of hydrogen is crucial. Electrochemical water splitting is likely one of the most valuable technique to produce hydrogen because the process is environmentally friendly b…

NANOSTRUCTURED ELECTRODES FOR HYDROGEN PRODUCTION IN ALKALINE ELECTROLYZER

Boosting DMFC power output by adding sulfuric acid as a supporting electrolyte: Effect on cell performance equipped with platinum and platinum group …

2023

Direct methanol fuel cells (DMFCs) are promising electrochemical systems capable of producing electricity from the electrochemical oxidation of methanol and the reduction of oxygen. In this work, the effectiveness of the addition of sulfuric acid as a supporting electrolyte for methanol fuel composition was assessed. The results showed that the peak of power curve in DMFCs with Pt/C cathode electrocatalysts increased progressively from 70 mW cm−2 (0 mM of H2SO4) to 115 mW cm−2 with a concentration of 100 mM of H2SO4. These results underlined the positive effect of the addition of a supporting electrolyte in the methanol aqueous solution on the electrochemical output that was enhanced. Plati…