1,721,055 research outputs found
“Metabolomics applied to the characterization of metabolic phenotypes in relation to positivity to Helicobacter pylori”
No full textThe aim of this study is to propose a new experimental approach, that, by using complementary analytical platforms, such as nuclear magnetic resonance (NMR) and liquid chromatography mass spectrometry (LC/MS), in association with mathematics and statistical mutivariate analyses (PCA and PLS), could provide a framework of the relationship Helicobacter Pylory – guest.
The study was carried out of healthy a non healthy people, with two different metabolomic approaches, one aimed to determine the urine metabolic profile by means of NMR and the other to determine plasma content of vitamin A (retinol) and carotenoids, by means of LC/MS .
The objective of this study was to investigate the possibility to individuate a metabolic profile in plasma and urine samples correlated with the positivity to Helicobacter Pylori infection as evaluated by Urea breath test. In this study we have examined eighty individuals, 40 negative and 40 positive matched for age
PLS analyses has evidenced that this study fit well for female subjects, where we can find higher concentration of 3OH-Isovaleric acid, Alanine, Lysine and 4OH-Phenyl Acetic acid in comparison to negative subjects. The urinary metabolic profile of Hp positive female was characterized also by lower levels of ζ-carotene. Furthermore,Increased urinary excretion of 3OH-Isovaleric acid, in female subjects, has been found to be an early and sensitive indicator of biotin deficiency. Biotin is a covalently bound prosthetic group for 4 mammalian carboxylases; one of these, methylcrotonyl-CoA carboxylase that catalyzes an essential step in the intermediarymetabolism of the branched-chain amino acid leucine. Decreased activity of methylcrotonyl- CoA carboxylase shunts the substrate 3-methylcrotonyl CoA to an alternate metabolic pathway, producing 3OH-Isovaleric acid, which is then excreted in urine
Applications of NMR-metabolomics to the study of foodstuffs: truffle, kiwifruit, lettuce, and sea bass
No full textIn this review, four examples of the NMRmetabolomic approach to foodstuff investigation
are reported. Different types of foodstuff of different origin (namely truffle, kiwifruit,
lettuce, and sea bass), with different metabolite composition, processing, and storage
procedures have been chosen to demonstrate the versatility and potentiality of NMR in the
foodstuff analysis. Fundamental aspects ofNMRmethodology such as sample preparation,
metabolites extraction, quantitative elaboration of spectral data, and statistical analysis have
been described. Metabolic profilings of aqueous and/or organic extracts as obtained by
one- and two-dimensional NMR experiments have been reported together with the results
obtained from their statistical elaboration. Discrimination between wild and farmed sea
bass and between genetically modified and wild lettuces as well as changes in the kiwifruit
metabolic profiles monitored over the season have been investigated. For each foodstuff,
some complementary findings provided by other analytical methods are also described
to underline the importance of different analytical approaches to explore specific aspects
related to foodstuf
Diffusion-Ordered NMR Spectroscopy: A Versatile Tool for the Molecular Weight Determination of Uncharged Polysaccharides
No full textDiffusion-ordered NMR spectroscopy (DOSY) experiments have been carried out on dilute aqueous solutions of uncharged saccharide systems and, in particular, on six well characterized pullulan fractions of different molecular weights. The values of diffusion coefficients and hydrodynamic radii determined for the pullulan
fractions are in good agreement with the results obtained with other methodologies such as light scattering.
Fitting the diffusion coefficients data as a function of the molecular weight allows for the determination of
a calibration curve that can be applied to a wide range of mono-, oligo-, and polysaccharides. Therefore,
DOSY is proposed as a versatile tool for achieving a simple estimation of the molecular weight of uncharged
polysaccharides. Mixtures of homopolymers of different molecular weight can be nicely separated. An
advantage of the method is that the same sample used for the NMR characterization can be used for the
molecular weight determination without any further manipulation. Other water soluble polymers, such as
poly(ethylene oxide) and poly(vinylpyrrolidone), can be roughly characterized using the same calibration
curve
Synthesis and association properties of thermoresponsive and permanently cationic charged block copolymers
No full textAtom transfer radical polymerization (ATRP) was used to prepare thermosensitive cationic block copolymers of (3-acrylamidopropyl)-trimethylammonium chloride (AMPTMA) and N-isopropylacrylamide (NIPAAM) with different block lengths. By using ethyl-2-chloropropionate (ECP) as initiator and CuCl/CuCl(2)/tris(2-dimethylaminoethyl)amine (Me(6)TREN) catalytic system in DMF:water 50:50 (v/v) mixtures at 20 degrees C the polymerization was controlled. The association properties in NaCl aqueous solution were studied as a function of temperature and. polymer concentration by dynamic light scattering, NMR spectroscopy, fluorescence spectroscopy and energy filtered-transmission electron microscopy. The block copolymers formed micellar aggregates above the lower critical solution temperature (LCST) of pNIPAAM. The LCST is strongly influenced by the relative length of the two blocks and is significantly higher than that of pure pNIPAAM. The size of core and shell of the micelles is discussed in terms of block copolymer composition. (C) 2008 Elsevier Ltd. All rights reserved
Polymerization, grafting and adsorption in the presence of inorganic substrates: thermal polymerization of styrene with untreated and γ-irradiated silica gel as a case study
No full textThe search for innovative and well-defined organic-inorganic hybrid materials demands that the interplay between polymerization reactions, chemical reactivity, and physical adsorption be fully understood. We examine the case study of the thermal polymerization of styrene in the presence of silica, and the effect of pre-irradiation of silica with γ-rays. The effect of adsorption of styrene-derived radical species on the silica support and polymerization conditions on free and grafted (unextractable) polystyrenes and on polymerization mechanism is discussed on the basis of previous literature findings and new data. Evidence is provided of silica derivatization with various species besides polystyrene (13C CPMAS NMR), including products from a β-scission of the adsorbed radical intermediates ensuing oxygen donation from the silica network. The polymerization mechanism can be cationic as well as radical, depending on reaction conditions, and the cationic route prevails in the grafting of polystyrene from silica, resulting in a bimodal molecular weight distribution. © 2013 Elsevier Ltd. All rights reserved
Looking for New Hybrid Polymer Fillers: Synthesis of Nanosized α-Type Zr(IV) Organophosphonates through an Unconventional Topotactic Anion Exchange Reaction
No full textGels of α-type zirconium(IV) phosphate alkylphosphonates, ZP(C n)x, were prepared by reacting, at room temperature, propanol intercalated nanosized α-zirconium phosphate (α-ZrP) with propanol solutions of alkylphosphonic acids (H2Cn, n = number of carbon atoms in the alkyl chain = 4, 5, 6), with (H2C n/Zr) molar ratios in the range 0.4-4.0. 31P MAS NMR showed the presence of resonances due to the phosphate and phosphonate groups bonded to the Zr atoms mainly by three oxygen atoms, as in the α-type layer. The composition of the ZP(Cn)x materials, obtained by thermogravimetric analysis, ranges from x ≈ 0.2 to x ≈ 1.1. On the basis of the NMR data and of the analysis of the X-ray patterns of gels and powders, it is inferred that the ZP(Cn)x compounds have an α-type layered structure and that the reaction between α-ZrP and H2Cn is a topotactic anion exchange process. The evolution of the X-ray patterns during propanol deintercalation is consistent with a random distribution of the alkylphosphonate groups on the α-type layers which gives rise to porous pathways in the interlayer region. To test the possibility of using ZP(Cn)x as mechanical reinforcement of a polymer matrix, a starch membrane filled with 5 wt % ZP(C6) 0.54 was prepared and characterized by stress-strain mechanical tests. Besides an excellent flexibility, this membrane exhibited a proportional increase of the Young's modulus by 230% in comparison with neat starch
Synthesis and partial characterization of hydrogels obtained via glutaraldehyde crosslinking of acetylated chitosan and of hyaluronan derivatives
No full textHydrophilic networks based on functionalized hyaluronic acid and on partially acetylated chitosan, respectively, have been obtained. In the case of hyaluronic acid (HA), primary amino functionalities have been introduced along the polysaccharide chains. The ensuing derivatives, i.e., HA-lysine (HA-K), HAdiamino pentane (HA-DAP), and HA-glycine-lysine (HA-GK), have been characterized by high field NMR spectroscopy. NMR 2D-DOSY experiments have allowed us to optimize the purification procedure. Chitosan was made soluble in water by partial acetylation. Cross-linking reactions have been performed using glutaraldehyde. The obtained networks have been qualitatively characterized by means of 13C CP-MAS NMR technique. The hydrogels have been characterized also in terms of water uptake
La Risonanza Magnetica Nucleare e l’olio di oliva: caratterizzazione degli oli in base all’origine geografica e alla cultivar
No full textLayered zirconium alkylphosphates: Suitable materials for novel PFSA composite membranes with improved proton conductivity and mechanical stability
No full textNanosized α-layered monohydrogen zirconium phosphate (ZP) has been organically modified by reacting the monohydrogen phosphate groups with of 1,2 epoxydodecane solutions in tetrahydrofuran. The materials thus obtained (ZP(C12)x, with x in the range 0.74-2.1) have been characterized by TEM, thermogravimetric analysis, X-ray powder diffraction and solid state 13C CPMAS NMR. The functionalization leads to a disordered layer packing without substantial alteration of the inorganic framework of the α-layer of pristine ZP. Samples with x=0.74 and 1.15 have been used as fillers of membranes based on a recast short side chain perfluorinated ionomer with EW=830. Composite membranes with 5-15wt% filler loadings have been characterized by stress-strain mechanical tests, proton conductivity measurements and water uptake determinations under controlled conditions of temperature and relative humidity (RH). The presence of the filler results in a significant increase in the Young[U+05F3]s modulus of the neat ionomer up to a maximum of 55% and 67% at room temperature and at 80°C/70% RH, respectively. At 100°C and in the RH range 50-90%, the conductivity of the composite membranes is higher than that of the neat ionomer, and the proportional increase in conductivity (+72% for RH=50% and +32% for RH=90%) is maximum for 10wt% filler loading. Surprisingly, under the same conditions of temperature and RH, the hydration of the most conductive composite membrane is lower than the hydration of the neat ionomer
NMR Metabolic Profiling of Transgenic Maize with the Cry1A(b) Gene
No full textThe metabolic profiles of seeds from the transgenic maize variety 33P67 and of the corresponding
traditional variety were investigated using one- and two-dimensional NMR techniques. The transgenic
variety carries a functional Cry1A(b) gene, which confers to the plant the ability to produce Bt
insect toxin. About 40 water-soluble metabolites in the maize seed extracts were identified, providing
a more complete 1H and 13C NMR assignment with respect to the assignment reported in the
literature. In particular ethanol, lactic acid, citric acid, lysine, arginine, glycine-betaine, raffinose,
trehalose, R-galactose, and adenine were identified for the first time in the 1H NMR spectrum of
maize seeds extracts. The 1H spectra of transgenic and nontransgenic seed maize samples turned
out to be conservative, showing the same signals and therefore the same metabolites. However, a
higher concentration of ethanol, citric acid, glycine-betaine, trehalose, as well as of another
compound not yet completely identified, was observed in the transgenic extracts than in nontransgenic
samples. So, it was possible to discriminate between transgenic and nontransgenic metabolic
profilings through the use of an appropriate statistical analysis
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