Publications

Abstract Deuterated water (2H2O) is widely used for measuring de novo lipogenesis (DNL). 2H is incorporated into fatty acids via exchange between body water and the hydrogens of acetyl-CoA, malonyl-CoA, and NADPH. Previous studies concluded that these exchanges are incomplete; therefore, fatty acid 2H enrichment requires correcting. In mice, we measured the 2H enrichment of fatty acid positions 2 and 3 and methyl hydrogens from [U-2H7]glucose to determine 2H transfer from glucose to fatty acid via malonyl-CoA, NADPH, and acetyl-CoA, respectively. Positional fatty acid 2H enrichments were compared with 13C enrichment of the same sites from an equivalent amount of [U-13C6]glucose provided alongside the [U-2H7]glucose tracer. Transfer of glucose 2H to fatty acid position 2 and methyl sites was low (2H enrichment of 0.06 ± 0.01 and 0.14 ± 0.01 relative to 13C) indicating extensive exchange at both malonyl- and acetyl-CoA, respectively. Transfer of glucose 2H into fatty acid position 3 was more extensive (0.46 ± 0.04 relative to 13C, P < 10-5 vs. position 2), indicating a more limited exchange of those glucose hydrogens that were transferred via NADPH. However, mice provided with [U-13C6]glucose and 2H2O had equivalent 2H enrichments of fatty acid positions 2 and 3, suggesting that in this setting, NADPH and body water 2H had exchanged extensively. This is explained by contributions of substrates other than exogenous glucose to DNL coupled with their extensive 2H enrichment from 2H2O prior to DNL. Under such conditions, 2H enrichment of fatty acids from 2H2O does not need correction. Copyright © 2019 Belew et al.

Abstract Considering the high incidence level and mortality rate of ovarian cancer, particularly among the European female population, the carbohydrate antigen 125 (CA-125) was selected as the protein target for this study for the development of a MIP-based biosensor. This work presents the development of molecular imprinting polymers (MIPs) on gold electrode surface for CA-125 biomarker recognition. The preparation of the CA-125 imprinting was obtained by electropolymerization of pyrrole (Py) monomer in a gold electrode using cyclic voltammetry (CV) in order to obtain highly selective materials with great molecular recognition capability. The quantification of CA-125 biomarker was made through the comparison of two methods: electrochemical (square wave voltammetry -SWV) and optical transduction (surface plasmon resonance -SPR). SWV has been widely used in biological molecules analysis since it is a fast and sensitive technique. In turn, SPR is a non-destructive optical technique that provides high-quality analytical data of CA-125 biomarker interactions with MIP. Several analytical parameters, such as sensitivity, linear response interval, and detection limit were determined to proceed to the performance evaluation of the electrochemical and optical transduction used in the development of the CA-125 biosensor. The biosensor based in the electrochemical transduction was the one that presented the best analytical parameters, yielding a good selectivity and a detection limit (LOD) of 0.01 U/mL, providing a linear concentration range between 0.01 and 500 U/mL. This electrochemical biosensor was selected for the study and it was successfully applied in the CA-125 analysis in artificial serum samples with recovery rates ranging from 91 to 105% with an average relative error of 5.8%.

Abstract Mesoporous sorbent composites, evolving from previous work on microporous composites of polyanionic polysaccharides were developed with the purpose of increasing the sorptive features of the materials. Using the widely successful classical surfactant micelle approach, it was observed, in this particular case, that the composites remained essentially microporous. The alternative consisted on the application of deep eutectic solvents (DES). The most common DES (choline chloride + neutral hydrogen bond donor), were tested because of their advantages over other possibilities such as imidazolium-based ionic liquids: lower cost, easy in-house preparation, safe constituents and water stability and solubility. Possible mechanisms underlying the observed mesoporosity were discussed. The surface area ranged between 76 and 267 m(2)/g and the average pore size was in the range 3-5 nm. DES had not a negative effect on synthesis yields and, in the case of fucoidan, composites bearing a higher content of the biopolymer were produced. As a consequence and in line with the initial expectations these new composites revealed highly enhanced Pb (II) sorptive features comparatively to their microporous predecessors: chondroitin sulfate composites - up to a 5 fold capacity enhancement; fucoidan composites- up to a 3.5 fold capacity enhancement. The highest capacity was observed for the fucoidan composite prepared with choline chloride-ethyleneglycol DES, 79 mg Pb (II)/g, which is slightly above the highest value (77 mg Pb (II)/g) found in the literature for Pb (II) sorbents based on polysaccharides, sol-gels or their composites.

Abstract Nano carbons, such as graphene and carbon nanotubes, show very interesting electrochemical properties and are becoming a focus of interest in many areas, including electrodeposition of carbon-metal composites for battery application. The aim of this study was to incorporate carbon materials (namely oxidized multi-walled carbon nanotubes (ox-MWCNT), pristine multi-walled carbon nanotubes (P-MWCNT), and reduced graphene oxide (rGO)) into a metallic tin matrix. Formation of the carbon-tin composite materials was achieved by electrodeposition from a choline chloride-based ionic solvent. The different structures and treatments of the carbon materials will create metallic composites with different characteristics. The electrochemical characterization of Sn and Sn composites was performed using chronoamperometry, potentiometry, electrochemical impedance, and cyclic voltammetry. The initial growth stages of Sn and Sn composites were characterized by a glassy-carbon (GC) electrode surface. Nucleation studies were carried out, and the effect of the carbon materials was characterized using the Scharifker and Hills (SH) and Scharifker and Mostany (SM) models. Through a non-linear fitting method, it was shown that the nucleation of Sn and Sn composites on a GC surface occurred through a 3D instantaneous process with growth controlled by diffusion. According to Raman and XRD analysis, carbon materials were successfully incorporated at the Sn matrix. AFM and SEM images showed that the carbon incorporation influences the coverage of the surface as well as the size and shape of the agglomerate. From the analysis of the corrosion tests, it is possible to say that Sn-composite films exhibit a comparable or slightly better corrosion performance as compared to pure Sn films.

Abstract Cyclic voltammetry and controlled-potential electrolysis have been employed to investigate the reductive intramolecular cyclization of propargyl bromoethers derivatives, catalyzed by electrogenerated (1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane) nickel(I), [Ni(tmc)](+), as the catalyst, in N,N,N-trimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethylsulfonyl) imide, [N-1 1 1 2(OH)][NTf2] and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, [C(2)mim][NTf2] in the absence and in the presence of water. The results show that the reaction leads to the formation of the expected heterocyclic compounds, in moderate to good yields. These compounds are important intermediates in the synthesis of natural products with possible biological activities. (C) 2019 The Electrochemical Society.

Abstract Vanillin is a naturally occurring phenolic aldehyde that is world-wide known for its flavouring properties. This work reports an extensive experimental and computational study of its thermodynamic properties. The vapour pressures of crystalline and liquid phases of vanillin were measured in the following temperature ranges T = (321.0-350.7) K and (324.9-382.3) K respectively, using a static method based on diaphragm capacitance gauge. Additionally, the crystalline vapour pressures were also measured in the temperature interval T = (303.1-325.2) K, using a Knudsen mass-loss effusion technique. The standard molar enthalpies, entropies and Gibbs energies of sublimation and of vaporization, at selected reference temperatures, were derived from the vapour pressure measurements. The enthalpies of vaporization and of sublimation, at T = 298.15 K, were also determined using Calvet microcalorimetry and the standard (p degrees = 10(5) Pa) molar enthalpy of formation, in the crystalline phase, at T = 298.15 K, was derived from its standard massic energy of combustion measured by static-bomb combustion calorimetry. From the experimental results, the standard molar enthalpy of formation in the gaseous phase, at T = 298.15 K, was calculated and compared with the values estimated by employing quantum chemical calculations. To analyse the thermodynamic stability of vanillin, the standard Gibbs energies of formation in crystalline and gaseous phases were calculated. The molar enthalpy of fusion determined using DSC is compared with indirect results determined using Calvet microcalorimetry and vapour pressure measurements. (C) 2018 Elsevier Ltd.

Abstract Er3+/Yb3+ codoped NaGdF4 upconversion phosphor is synthesized by thermal decomposition route. The phase confirmation of synthesized sample is further confirmed by x-ray diffraction analysis. Particle size and elemental composition of phosphor is analyzed by field emission scanning electron microscopy (FESEM) and energy dispersive x-ray (EDX), respectively. The upconversion emission is measured by exciting the sample with 976 nm diode laser source. The fluorescence intensity ratio (FIR) of two close levels H-2(11/2) and S-4(3/2) is taken into account to study thermometry ability of sample for the temperature range of 301-506 K at a constant laser power (17.60 W cm(-2)). The sensor sensitivity of phosphor is found to 5.107 x 10(-3) K-1 at 301 K.

Abstract This work presents an extended study of the thermal behavior of the alkyl and dialkylpyridinium derivatives of the bis(trifluoromethylsulfonyl)imide ionic liquid series, using high resolution power compensation differential scanning calorimetry (DSC) equipment. Temperatures, enthalpies, entropies, and the heat capacity change associated with the glass transition, as well as cold crystallization, solid-solid transitions, and melting, are used to evaluate their ability to form a glass and crystallize. The effects of the cation isomerization and the alkyl chain length increase were used to investigate the nature of the irregular thermal behavior of ionic liquids in general and to establish the link between their thermal properties and nanostructuration. The observed V-shape profile of the melting temperatures versus the alkyl side-chain length is interpreted as a consequence of the balance between the initial decrease of the magnitude of the electrostatic interaction and the regular increase of the dispersive van der Waals forces. The observed differentiation between the thermal behavior below and above the critical alkyl size, CAS, is analyzed and compared with the regular behavior of both the n-alkanes and the n-alkanols. Above the CAS, the entropy and enthalpy profiles present trends similar to those observed in the alkane and alcohol series, contrasting with those observed in the molten salts-like region. These results and evidence are a strong support to the interpretation of the effect of the ILs nanostructuration in the physical-chemical properties. We found a great similarity between the thermal behavior of the imidazolium and pyridinium cation core, highlighting the strong ability of ILs to form a nanostructured network with distinguishable polar and nonpolar domains in the liquid phase.