Prediction of physical-chemical properties of crude oils by 1H NMR analysis of neat samples and chemometrics.

In this work, we report the feasibility study to predict the properties of neat crude oil samples from 300-MHz NMR spectral data and partial least squares (PLS) regression models. The study was carried out on 64 crude oil samples obtained from 28 different extraction fields and aims at developing a rapid and reliable method for characterizing the crude oil in a fast and cost-effective way. The main properties generally employed for evaluating crudes' quality and behavior during refining were measured and used for calibration and testing of the PLS models.

NMR investigation of imidazolium-based ionic liquids and their aqueous mixtures.

(1)H and (13)C NMR spectroscopy is employed to investigate the interaction of water with two imidazolium-based ionic liquids (ILs), 1-hexyl-3-methylimidazolium bromide ([C(6)mim]Br) and 1-octyl-3-methylimidazolium bromide ([C(8)mim]Br), at IL concentrations well above the critical aggregation concentration (CAC). The results are compared with those of the neat samples. To this aim, a detailed analysis of the changes in the (1)H chemical shifts, (13)C relaxation parameters, and 2D ROESY data due to the presence of water is performed.

1H NMR-based metabolomic analysis of urine from preterm and term neonates.

Metabolomics is a technique used to non-invasively determine metabolic status of an organism. Aim of our study was to analyze urinary metabolic profiles in term and preterm infants in order to identify gestational age-related metabolic differences and to predict metabolic maturity at birth. Twenty-six healthy term infants and 41 preterm infants were prospectively enrolled.

A metabolomic approach in an experimental model of hypoxia-reoxygenation in newborn piglets: urine predicts outcome.

Perinatal asphyxia is one of the leading causes of morbidity and mortality in the neonatal period. Response to oxygen treatment is unpredictable and the optimum concentration of oxygen in neonatal resuscitation is still a matter of debate among neonatologists. A metabolomic approach was used to characterize the metabolic profiles of newborn hypoxic-reoxygenated piglets.

Highlighting cavities in proteins by NMR using sulfur hexafluoride as a spy molecule.

Cavities in proteins can be studied experimentally by using some detectable atoms, such as xenon, or molecules which act as reporter, such as a spy. The interest of sulfur hexafluoride (SF(6)) for probing hydrophobic cavities by solution-state NMR is investigated. The wheat nonspecific lipid transfer protein (LTP) was selected as a model system for this purpose.

1H NMR-based metabolic profiling of urine from children with nephrouropathies.

Pediatric nephrourological diseases are associated with functional alterations frequently related to inflammatory states. A feedback loop adjusts urinary system function while forcing adaptation to internal and external influences during disease development and as a result of treatment. We hypothesized that nephrourological dysfunction would alter the urine metabolite pattern in children in a defined manner.

Competitive binding exchange between alkali metal ions (K+, Rb+, and Cs+) and Na+ ions bound to the dimeric quadruplex [d(G4T4G4)]2: a 23Na and 1H NMR study.

A comparative study of the competitive cation exchange between the alkali metal ions K+, Rb+, and Cs+ and the Na+ ions bound to the dimeric quadruplex [d(G4T4G4)]2 was performed in aqueous solution by a combined use of the 23Na and 1H NMR spectroscopy. The titration data confirm the different binding affinities of these ions for the G-quadruplex and, in particular, major differences in the behavior of Cs+ as compared to the other ions were found. Accordingly, Cs+ competes with Na+ only for the binding sites at the quadruplex surface (primarily phosphate groups), while K+ and Rb+ are also able to replace sodium ions located inside the quadruplex.

Probing systems in solution by NMR using sulfur hexafluoride as a spy molecule.

The use of SF6 as a spy molecule in solution-state NMR is investigated as an alternative to 129Xe NMR. 19F chemical shift, longitudinal relaxation time, and integral measurements, as well as intermolecular nuclear Overhauser effects, are reported for SF6 dissolved in simple deuterated solvents and/or in various solutions among which are aqueous solutions of cucurbit[6]uril (CB) and alpha-cyclodextrin (alphaCD). Both CB and alphaCD form a 1:1 inclusion complex with SF6.

NMR study of the reversible trapping of SF6 by cucurbit[6]uril in aqueous solution.

The complexation of sulfur hexafluoride (SF(6)), a highly potent greenhouse gas, by cucurbit[6]uril (CB) was studied at various temperatures in Na(2)SO(4) aqueous solutions by (19)F and (1)H NMR. CB shows a remarkable affinity for SF(6), suggesting that it is a suitable molecular container for the design of materials tailored for SF(6) trapping. At 298 K, the equilibrium constant characterizing the inclusion of SF(6) by CB is 3.

Effect of rubidium and cesium ions on the dimeric quaduplex formed by the Oxytricha nova telomeric repeat oligonucleotide d(GGGGTTTTGGGG).

The DNA sequence d(GGGGTTTTGGGG) consists of 1.5 units of the repeat in telomeres of Oxytricha nova. It has been shown by NMR and x-ray crystallographic analysis that it is capable to form a dimeric quadruplex structure and that a variety of cations, namely K(+), Na(+), and NH(4)(+), are able to interact with this complex with different affinity, leading to complexes characterized by different local conformations.

Wheat bran biodegradation by Pleurotus ostreatus: a solid-state carbon-13 NMR study.

Solid-state (13)C nuclear magnetic resonance (NMR) and elemental analysis techniques were used to monitor the degradation of wheat bran by the white-rot fungus Pleurotus ostreatus during a 62-day cultivation period. The weight loss and in vitro organic matter digestibility of the substrate were also evaluated after fungal treatment. The (13)C NMR spectra of degraded wheat bran samples showed a lower content in carbohydrates and a higher content in aliphatic and carboxylic groups than the untreated control sample.

13C-CPMAS and 1H-NMR study of the inclusion complexes of beta-cyclodextrin with carvacrol, thymol, and eugenol prepared in supercritical carbon dioxide.

Beta-cyclodextrin (beta-CD) inclusion complexes with carvacrol (1), thymol (2), and eugenol (3) (components of essential oils of vegetable origin) were prepared by the supercritical CO2 technique, and their structural characterization was achieved by means of 1H-NMR in aqueous solution and 13C-CPMAS NMR in the solid state. Evidence of the formation of the inclusion complexes for all the examined systems was obtained by 1H-NMR in solution, while 2D-ROESY-NMR experiments were used to investigate the geometry of inclusion. In addition, the dynamics of these inclusion complexes in the kHz timescale was investigated by analysis of the 1H and 13C spin-lattice relaxation times in the rotating frame.

Binding of Mg2+, Cd2+, and Ni2+ to liquid crystalline NaDNA: polarized light microscopy and NMR investigations.

The interaction of the divalent metal ions Mg(2+), Cd(2+), and Ni(2+) with liquid crystalline NaDNA solutions (molar ratios Me(2+)/DNA-phosphate View Article and Find Full Text PDF

Imazalil-cyclomaltoheptaose (beta-cyclodextrin) inclusion complex: preparation by supercritical carbon dioxide and 13C CPMAS and 1H NMR characterization.

An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (beta-cyclodextrin, betaCD) was obtained using supercritical fluid carbon dioxide. The best preparation conditions were determined, and the inclusion complex was investigated by means of 1H NMR spectroscopy in aqueous solution and 13C CPMAS NMR spectroscopy in the solid state. Information on the geometry of the betaCD/IMZ complex was obtained from ROESY spectroscopy, while the dynamics of the inclusion complex in the kilohertz range was obtained from the proton spin-lattice relaxation times in the rotating frame, T(1rho) (1H).

Characterization of the wound-induced material in Citrus paradisi fruit peel by carbon-13 CP-MAS solid state NMR spectroscopy.

Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated under conditions favourable for the accumulation of defence related material. Histochemical examination revealed that tissues adjacent to inoculated injuries contained phloroglucinol-HCl (PG-HCl) reactive material. Solvent washed cell wall preparations of intact and injured-inoculated peel were further purified using a mixture of cell wall degrading enzymes.

15N and 13C NMR study of protonated monoaminopyridines in CDCl3-DMSO.

The 2-, 3- and 4-amino-pyridine and their protonated forms, obtained by reaction with pyridinium chloride, were investigated by 15N NMR spectroscopy. Exhaustive evidence has been found that the protonation occurs mainly on the annular nitrogen. Protonation of 4-aminopyridine by dehydrohalogenation of 1,1,2,2-tetrachloroethane (TCE) was also studied by 13C NMR spectroscopy, which indicated that the protonation occurs via the formation of adducts.

Solid-state 13C NMR study of poly(vinyl alcohol) gels.

Poly(vinyl alcohol) (PVA) with 55% and 61% syndiotacticity, and their related dry and hydrated gels obtained by two different freeze-thawing cycles have been investigated using the solid-state 13C CP-MAS NMR technique. From a comparative analysis of the spectra, evidence was obtained that the gelation process largely disrupts the intramolecular hydrogen-bonded network of the PVA. The addition of water to the dry gels favours their swelling, destroying intra-chain hydrogen bonds between hydroxyl groups as a function of the degree of tacticity and the gelation procedure, and promotes the formation of new networks of interchain hydrogen bonds.

Multinuclear NMR investigation of the NaDNA/ethidium bromide anisotropic system.

A combined use of (31)P, (23)Na, (2)H and (17)O NMR spectroscopies and polarized light microscopy has been employed to investigate the effect of the ethidium bromide (EB) binding on the liquid crystalline phase of concentrated double stranded DNA solutions. The optical textures and the (31)P and (23)Na NMR spectra of the DNA anisotropic solutions show that the intercalation of EB induces significant modifications either in the arrangements of the DNA rods and the surrounding ionic atmosphere. On the contrary, no indication of significant changes of the orientational order of the water molecules around DNA emerges from the water (2)H and (17)O NMR spectra.