Processos de purificação/ valorização do glicerol proveniente da produção de biodiesel

Mestrado em Engenharia Química - Ramo optimização energética na indústria química

Metabolic and respiratory effects of infused sodium acetate in healthy human subjects.

The metabolic and respiratory effects of intravenous 0.5 M sodium acetate (at a rate of 2.5 mmol/min during 120 min) were studied in nine normal human subjects. O2 consumption (VO2) and CO2 production (VCO2) were measured continuously by open-circuit indirect calorimetry. VO2 increased from 251 +/- 9 to 281 +/- 9 ml/min (P < 0.001), energy expenditure increased from 4.95 +/- 0.17 kJ/min baseline to 5.58 +/- 0.16 kJ/min (P < 0.001), and VCO2 decreased nonsignificantly (211 +/- 7 ml/min vs. 202 +/- 7 ml/min, NS). The extrapulmonary CO2 loss (i.e., bicarbonate generation and excretion) was estimated at 48 +/- 5 ml/min. This observation is consistent with 1 mol of bicarbonate generated from 1 mol of acetate metabolized. Alveolar ventilation decreased from 3.5 +/- 0.2 l/min basal to 3.1 +/- 0.2 l/min (P < 0.001). The minute ventilation (VE) to VO2 ratio decreased from 22.9 +/- 1.3 to 17.6 +/- 0.9 l/l (P < 0.005), arterial PO2 decreased from 93.2 +/- 1.9 to 78.7 +/- 1.6 mmHg (P < 0.0001), arterial PCO2 increased from 39.2 +/- 0.7 to 42.1 +/- 1.1 mmHg (P < 0.0001), pH from 7.40 +/- 0.005 to 7.50 +/- 0.007 (P < 0.005), and arterial bicarbonate concentration from 24.2 +/- 0.7 to 32.9 +/- 1.1 (P < 0.0001). These observations indicate that sodium acetate infusion results in substantial extrapulmonary CO2 loss, which leads to a relative decrease of total and alveolar ventilation.

A Preliminary Investigation on the Chemical Composition of the Cell Surface of Five Enteropathogenic Escherichia coli Serotypes

The cell surfaces of five enteropathogenic Escherichia coli serotypes (O111:H2; O111:H12; O125:H9; O119:H6; O26:H11) were assayed by chemical methods, lectin agglutination tests and spectroscopy associated to transmission electron microscopy. Results of lectin agglutination assays showed that all strains reacted with mannosebinding lectins. Strains belonging to serotype O125:H9 also agglutinated with lectins which recognize galactose and Nacetylgalactosamine residues. The bacterial cells were treated with 0.01M phosphate buffered saline (pH 7.0) at 100oC for 2 hr and the extracts were submitted to precipitation and fractionated by Cetavlon. Phosphate, total sugar and protein contents were determined. Gas liquid chomatography-mass spectrometry analysis of alditol acetates showed the presence of galactose, mannose, fucose, glucose and traces of ribose. Spectroscopic analysis of intact cells showed the presence of a capsule-like structure which was not totally preserved after extraction. Some cells were still surrounded by an amorphous capsular-like material after polysaccharide extraction.

Stimulation-induced increases of astrocytic oxidative metabolism in rats and humans investigated with 1-11C-acetate

The purpose of this study was to investigate astrocytic oxidative metabolism using 1-(11)C-acetate. 1-(11)C-acetate kinetics were evaluated in the rat somatosensory cortex using a beta-scintillator during different manipulations (test-retest, infraorbital nerve stimulation, and administration of acetazolamide or dichloroacetate). In humans a visual activation paradigm was used and kinetics were measured with positron emission tomography. Data were analyzed using a one-tissue compartment model. The following features supported the hypothesis that washout of radiolabel (k(2)) is because of (11)C-CO(2) and therefore related to oxygen consumption (CMRO(2)): (1) the onset of (11)C washout was delayed; (2)k(2) was not affected by acetazolamide-induced blood flow increase; (3)k(2) demonstrated a significant increase during stimulation in rats (from 0.014+/-0.007 to 0.027+/-0.006 per minute) and humans (from 0.016+/-0.010 to 0.026+/-0.006 per minute); and (4) dichloroacetate led to a substantial decrease of k(2). In the test-retest experiments K(1) and k(2) were very stable. In summary, 1-(11)C-acetate seems a promising tracer to investigate astrocytic oxidative metabolism in vivo. If the washout rate indeed represents the production of (11)C-CO(2), then its increase during stimulation would point to a substantially higher astrocytic oxidative metabolism during brain activation. However, the quantitative relationship between k(2) and CMRO(2) needs to be determined in future experiments.

In vivo enzymatic activity of acetylCoA synthetase in skeletal muscle revealed by 13C turnover from hyperpolarized [1-13C]acetate to [1-13C]acetylcarnitine

BACKGROUND: Acetate metabolism in skeletal muscle is regulated by acetylCoA synthetase (ACS). The main function of ACS is to provide cells with acetylCoA, a key molecule for numerous metabolic pathways including fatty acid and cholesterol synthesis and the Krebs cycle. METHODS: Hyperpolarized [1-(13)C]acetate prepared via dissolution dynamic nuclear polarization was injected intravenously at different concentrations into rats. The (13)C magnetic resonance signals of [1-(13)C]acetate and [1-(13)C]acetylcarnitine were recorded in vivo for 1min. The kinetic rate constants related to the transformation of acetate into acetylcarnitine were deduced from the 3s time resolution measurements using two approaches, either mathematical modeling or relative metabolite ratios. RESULTS: Although separated by two biochemical transformations, a kinetic analysis of the (13)C label flow from [1-(13)C]acetate to [1-(13)C]acetylcarnitine led to a unique determination of the activity of ACS. The in vivo Michaelis constants for ACS were KM=0.35±0.13mM and Vmax=0.199±0.031μmol/g/min. CONCLUSIONS: The conversion rates from hyperpolarized acetate into acetylcarnitine were quantified in vivo and, although separated by two enzymatic reactions, these rates uniquely defined the activity of ACS. The conversion rates associated with ACS were obtained using two analytical approaches, both methods yielding similar results. GENERAL SIGNIFICANCE: This study demonstrates the feasibility of directly measuring ACS activity in vivo and, since the activity of ACS can be affected by various pathological states such as cancer or diabetes, the proposed method could be used to non-invasively probe metabolic signatures of ACS in diseased tissue.

Cis-configured aziridines are new pseudo-irreversible dual-mode inhibitors of Candida albicans secreted aspartic protease 2

A series of cis-configured epoxides and aziridines containing hydrophobic moieties and amino acid esters,were synthesized as new potential inhibitors of the secreted aspartic protease 2 (SAP2) of Candida albicans. Enzyme assays revealed the N- benzyl-3-phenyl-substituted aziridines 11 and 17 as the most potent inhibitors, with second-order inhibition, rate constants (k(2)) between 56000 and 12-1000 M-1 min(-1). The compounds were shown to be pseudo-irreversible dual-mode, inhibitors: the interm ediate esterified enzyme resulting from nucleophilic ring opening was hydrolyzed and yielded amino alcohols as transition state-mimetic reversible inhibitors. The results of docking studies with the ring-closed aziridine forms of the inhibitors suggest binding modes mainly dominated by hydrophobic interactions with the S1, S1' S2, and S2' subsites of the protease, and docking studies with the processed amino alcohol forms predict additional hydrogen bonds of the new hydroxy group to the active site Asp residues. C. albicans growth assays showed the compounds to decrease SAP2-dependent growth while not affecting SAP2-independent growth.

Effect of ethanol on energy expenditure.

The thermogenic response induced by ethanol ingestion in humans has not been extensively studied. This study was designed to determine the thermic effect of ethanol added to a normal diet in healthy nonalcoholic subjects, using indirect calorimetry measurements over a 24-h period in a respiration chamber. The thermic effect of ethanol was also measured when ethanol was ingested in the fasting state, using a ventilated hood system during a 5-h period. Six subjects ingested 95.6 +/- 1.8 (SE) g ethanol in 1 day partitioned over three meals; there was a 5.5 +/- 1.2% increase in 24-h energy expenditure compared with a control day in which all conditions were identical except that no ethanol was consumed. The calculated ethanol-induced thermogenesis (EIT) was 22.5 +/- 4.7% of the ethanol energy ingested. Ingestion of 31.9 +/- 0.6 g ethanol in the fasting state led to a 7.4 +/- 0.6% increase in energy expenditure over baseline values, and the calculated EIT was 17.1 +/- 2.2%. It is concluded that in healthy nonalcoholic adults ethanol elicits a thermogenic response equal to approximately 20% of the ethanol energy. Thus the concept of the apparently inefficient utilization of ethanol energy is supported by these results which show that only approximately 80% of the ethanol energy is used as metabolizable energy for biochemical processes in healthy nonalcoholic moderate ethanol consumers.

Citrate- vs. acetate-based dialysate in bicarbonate haemodialysis: consequences on haemodynamics, coagulation, acid-base status, and electrolytes.

BACKGROUND: A concentrate for bicarbonate haemodialysis acidified with citrate instead of acetate has been marketed in recent years. The small amount of citrate used (one-fifth of the concentration adopted in regional anticoagulation) protects against intradialyser clotting while minimally affecting the calcium concentration. The aim of this study was to compare the impact of citrate- and acetate-based dialysates on systemic haemodynamics, coagulation, acid-base status, calcium balance and dialysis efficiency. METHODS: In 25 patients who underwent a total of 375 dialysis sessions, an acetate dialysate (A) was compared with a citrate dialysate with (C+) or without (C) calcium supplementation (0.25 mmol/L) in a randomised single-blind cross-over study. Systemic haemodynamics were evaluated using pulse-wave analysis. Coagulation, acid-base status, calcium balance and dialysis efficiency were assessed using standard biochemical markers. RESULTS: Patients receiving the citrate dialysate had significantly lower systolic blood pressure (BP) (-4.3 mmHg, p < 0.01) and peripheral resistances (PR) (-51 dyne.sec.cm-5, p < 0.001) while stroke volume was not increased. In hypertensive patients there was a substantial reduction in BP (-7.8 mmHg, p < 0.01). With the C+ dialysate the BP gap was less pronounced but the reduction in PR was even greater (-226 dyne.sec.cm-5, p < 0.001). Analyses of the fluctuations in PR and of subjective tolerance suggested improved haemodynamic stability with the citrate dialysate. Furthermore, an increase in pre-dialysis bicarbonate and a decrease in pre-dialysis BUN, post-dialysis phosphate and ionised calcium were noted. Systemic coagulation activation was not influenced by citrate. CONCLUSION: The positive impact on dialysis efficiency, acid-base status and haemodynamics, as well as the subjective tolerance, together indicate that citrate dialysate can significantly contribute to improving haemodialysis in selected patients.

Localized in vivo hyperpolarization transfer sequences.

In vivo localized and fully adiabatic homonuclear and heteronuclear polarization transfer experiments were designed and performed in the rat brain at 9.4 T after infusion of hyperpolarized sodium [1,2-(13)C(2)] and sodium [1-(13)C] acetate. The method presented herein leads to highly enhanced in vivo detection of short-T(1) (13)C as well as attached protons. This indirect detection scheme allows for probing additional molecular sites in hyperpolarized substrates and their metabolites and can thus lead to improved spectral resolution such as in the case of (13)C-acetate metabolism.

1H-[13C] NMR spectroscopy of the rat brain during infusion of [2-13C] acetate at 14.1 T.

Full signal intensity (1)H-[(13)C] NMR spectroscopy, combining a preceding (13)C-editing block based on an inversion BISEP (B(1)-insensitive spectral editing pulse) with a spin-echo coherence-based localization, was developed and implemented at 14.1 T. (13)C editing of the proposed scheme was achieved by turning on and off the (13)C adiabatic full passage in the (13)C-editing block to prepare inverted and noninverted (13)C-coupled (1)H coherences along the longitudinal axis prior to localization. The novel (1)H-[(13)C] NMR approach was applied in vivo under infusion of the glia-specific substrate [2-(13)C] acetate. Besides a approximately 50% improvement in sensitivity, spectral dispersion was enhanced at 14.1 T, especially for J-coupled metabolites such as glutamate and glutamine. A more distinct spectral structure at 1.9-2.2 ppm(parts per million) was observed, e.g., glutamate C3 showed a doublet pattern in both simulated (1)H spectrum and in vivo (13)C-edited (1)H NMR spectra. Besides (13)C time courses of glutamate C4 and glutamine C4, the time courses of glutamate C3 and glutamine C3 obtained by (1)H-[(13)C] NMR spectroscopy were reported for the first time. Such capability should greatly improve the ability to study neuron-glial metabolism using (1)H-observed (13)C-edited NMR spectroscopy.

Quadratic tranverse anisotropy term due to dislocations in Mn12 acetate crystals directly observed by EPR spectroscopy

High-sensitivity electron paramagnetic resonance experiments have been carried out in fresh and stressed Mn12 acetate single crystals for frequencies ranging from 40 GHz up to 110 GHz. The high number of crystal dislocations formed in the stressing process introduces a E(Sx2-Sy2) transverse anisotropy term in the spin Hamiltonian. From the behavior of the resonant absorptions on the applied transverse magnetic field we have obtained an average value for E=22 mK, corresponding to a concentration of dislocations per unit cell of c=10-3.

Bonding Agents for Portland Cement Concrete and Mortar, August 1983

Structural repairs of bridges piers and abutments require patching concrete or mortar be placed at various thickness. Whether concrete or mortar is use depends upon the depth of the patch to be made. In some instances, the use of a liquid bonding agent has been specified in the mixes as well as in a grout scrubbed onto the surface to be patched prior to the mix placement. Most of the bonding agents presently approved by the Iowa D.O.T. are polyvinyl acetate (PVA) or some type of latex. In a general discussion with a consultant about various types of bridge repair materials and processes, the subject of bonding agents was discussed at some length. It was the opinion of the consultant that the usage of polyvinyl acetates should be discontinued because of possible deterioration of this material with time. Some of these materials apparently re-emulsify in a high - moisture environment causing serious patch deterioration. As a result of this information, a study was initiated to determine the durability of these materials.

Herbivory in the previous generation primes plants for enhanced insect resistance.

Inducible defenses, which provide enhanced resistance after initial attack, are nearly universal in plants. This defense signaling cascade is mediated by the synthesis, movement, and perception of jasmonic acid and related plant metabolites. To characterize the long-term persistence of plant immunity, we challenged Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum) with caterpillar herbivory, application of methyl jasmonate, or mechanical damage during vegetative growth and assessed plant resistance in subsequent generations. Here, we show that induced resistance was associated with transgenerational priming of jasmonic acid-dependent defense responses in both species, caused caterpillars to grow up to 50% smaller than on control plants, and persisted for two generations in Arabidopsis. Arabidopsis mutants that are deficient in jasmonate perception (coronatine insensitive1) or in the biogenesis of small interfering RNA (dicer-like2 dicer-like3 dicer-like4 and nuclear RNA polymerase d2a nuclear RNA polymerase d2b) do not exhibit inherited resistance. The observation of inherited resistance in both the Brassicaceae and Solanaceae suggests that this trait may be more widely distributed in plants. Epigenetic resistance to herbivory thus represents a phenotypically plastic mechanism for enhanced defense across generations.

Structures of ethylenediaminetetraacetato (3-) metal complexes. I complexes with Co, Mg and Cd metals

(I): Hexaaquacobalt(II) aqua[ethylenediaminetetraacetato(3-)]cobaltate(II) dihydrate, [Co(H2O)6][Co(C10H13N2O8)(H2O)]2.2H2O (Ibis): Hexaaquamagnesium(II) aqua[ethylenediaminetetraacetato(3-)]magnesiate(II) dihydrate, [Mg(H2O)6][Mg(C10H13N2O8)(H2O)]2.2H2O (II):Tetraaquabis{aqua[ethylenediaminetetraacetato(3-)]cadmium(II)-O-O'}Cadmium(II) tetrahydrate