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121.
Gari V. Ccana-Ccapatinta Bruno L. Sampaio Fernando M. dos Santos João M. Batista Fernando B. Da Costa 《Tetrahedron: Asymmetry》2017,28(12):1823-1828
Recently, it was observed that infrared (IR) and vibrational circular dichroism (VCD) calculations including deuterated hydroxyl groups in phenolic and saccharide moieties improved significantly the agreement with experimental data obtained in methanol-d4. In the present study, the relative and absolute configurations of three methanol-soluble caffeic acid ester derivatives 1–3, isolated from Tithonia diversifolia, were established by a combined use of experimental and calculated 13C NMR chemical shifts, as well as electronic circular dichroism (ECD) and VCD spectroscopies. Interestingly, the attempt to reproduce the deuteration pattern arising from possible isotopic exchange in methanol-d4 solution led to nearly mirror image calculated VCD spectra for 1 when compared to the non-deuterated molecule with the same absolute configuration. This latter fact can potentially lead to absolute configuration misassignments. A closer inspection of the vibrational chiroptical properties of 1 revealed that the deuteration status of the tertiary hydroxyl group at C-2 is critical for the correct reproduction of experimental VCD data in protic solvents. Therefore, in the case of stereochemical analysis of polar chiral natural product molecules, a combination of VCD and ECD is recommended. 相似文献
122.
Daiane Cristina Sass Vladimir Constantino Gomes Heleno Jader da Silva Barbosa Gustavo Oliveira Morais Fernando Batista Da Costa Mauricio Gomes Constantino 《Tetrahedron letters》2013,54(7):625-627
The conversion of a germacranolide structure (tagitinin C) into a furanoheliangolide one (diversifolin) was achieved by hydride conjugate addition using Stryker’s reagent. 相似文献
123.
Janaina Aparecida Teixeira João Batista Ribeiro Daniel Bonoto Gonçalves Marisa Vieira de Queiroz Elza Fernandes de Araújo 《Applied biochemistry and biotechnology》2013,169(6):1965-1977
Inactivation of the pgg2 gene, a polygalacturonase-encoding gene from Penicillium griseoroseum, reduced the total activity of polygalacturonase (PG) by 90 % in wild-type P. griseoroseum, which indicates that the pgg2 gene is the major gene responsible for PG production in this species. To increase PG production, the coding region of the pgg2 gene was cloned under the control of the glyceraldehyde 3-phosphate dehydrogenase (gpd) promoter and the terminator region of the tryptophan synthase (trpC) gene from Aspergillus nidulans (pAN52pgg2 vector). This vector was then used to transform P. griseoroseum. The transformed strains were characterized according to PG production using glucose, sucrose, or sugar cane juice as the carbon sources. The recombinant P. griseoroseum T146 strain contained an additional copy of the pgg2 gene, which resulted in a 12-fold increase in PG activity when compared with that detected in the supernatant of the control PG63 strain. The proteins secreted by the recombinant strain T146 showed a strong band at 38 kDa, which corresponds to the molecular weight of PG of the P. griseoroseum. The results demonstrate the significant biotechnological potential of recombinant P. griseoroseum T146 for use in PG production. 相似文献
124.
Graciela Salete Centenaro Myriam Salas-Mellado Carla Pires Irineu Batista Maria L. Nunes Carlos Prentice 《Applied biochemistry and biotechnology》2014,172(6):2877-2893
In this work, chicken and fish peptides were obtained using the proteolytic enzymes α-Chymotrypsin and Flavourzyme. The muscle was hydrolyzed for 4 h, and the resulting peptides were evaluated. Hydrolysates were produced from Argentine croaker (Umbrina canosai) with a degree of hydrolysis (DH) of 25.9 and 27.6 % and from chicken (Gallus domesticus) with DH of 17.8 and 20.6 % for Flavourzyme and α-Chymotrypsin, respectively. Membrane ultrafiltration was used to separate fish and chicken hydrolysates from Flavourzyme and α-Chymotrypsin based on molecular weight cutoff of >1,000, <1,000 and >500, and <500 Da, to produce fractions (F1,000, F1,000–500, and F500) with antioxidant activity. Fish hydrolysates produced with Flavourzyme (FHF) and α-Chymotrypsin showed 60.8 and 50.9 % of peptides with a molecular weight of <3 kDa in its composition, respectively. To chicken hydrolysates produced with Flavourzyme and α-Chymotrypsin (CHC) was observed 83 and 92.4 % of peptides with a molecular weight of <3 kDa. The fraction that showed, in general, higher antioxidant potential was F1,000 from FHF. When added 40 mg/mL of FHF and CHC, 93 and 80 % of lipid oxidation in ground beef homogenates was inhibited, respectively. The composition of amino acids indicated higher amino acids hydrophobic content and amino acids containing sulfuric residues for FHF, which showed antioxidant potential. 相似文献
125.
B. B. Romão F. R. X. Batista J. S. Ferreira H. C. B. Costa M. M. Resende V. L. Cardoso 《Applied biochemistry and biotechnology》2014,172(7):3670-3685
Nowadays, hydrogen produced globally has been synthesized from fossil fuel with limited source. Therefore, research has been developed in order to explore biological H2 production by dark fermentation. The purpose of this work was to evaluate the effect of initial pH and ferrous sulfate and ammonium sulfate concentrations on the production of biohydrogen by dark fermentation. The process was carried out in batch mode under anaerobic conditions, in the absence of light, and at standard room temperature and pressure. A microbial consortium provided by the effluent treatment plant of a local dairy company was inoculated into a synthetic medium supplemented with cheese whey permeate (20 g/L of lactose) as a carbon source. The influence of three variables was analyzed by a central composite design 2(3), and the optimum results of hydrogen yield (4.13 mol H2/mol lactose) and productivity (86.31 mmol H2/L/day) were achieved at initial pH 7.0 and FeSO4 and (NH4)2SO4 concentrations of 0.6 and 1.5 g/L, respectively. Under these conditions, the kinetic parameters of fermentation were investigated by analyzing the profile of H2 yield and productivity, metabolite concentrations, pH, and concentration of dissolved iron. In the kinetic analysis, the modified Gompertz equation described adequately the fermentative hydrogen production from cheese whey permeate (R 2?=?0.98). The profile of ethanol and volatile organic acids showed that lactic acid and butyric acid were the main metabolites produced, and the sum of both by-products corresponded to about 58 % of the total metabolites. 相似文献
126.
In type-II superconductors that contain a lattice of magnetic moments, vortices polarize the magnetic system inducing additional contributions to the vortex mass, vortex viscosity, and vortex-vortex interaction. Extra magnetic viscosity is caused by radiation of spin waves by a moving vortex. Like in the case of Cherenkov radiation, this effect has a characteristic threshold behavior and the resulting vortex viscosity may be comparable to the well-known Bardeen-Stephen contribution. The threshold behavior leads to an anomaly in the current-voltage characteristics, and a drop in dissipation for a current interval that is determined by the magnetic excitation spectrum. 相似文献
127.
de Araujo Márcio P. Queiroz Salete L. Batista Alzir A. Panepucci Ezequiel H. Oliva Glaucius Castellano E.E. 《Transition Metal Chemistry》2002,27(1):110-114
The triply chloro-bridged binuclear complexes [Ph3X=O···H···O=XPh3][Ru2Cl7(XPh3)2]·0.5(CH2Cl2)(H2O) (X = As or P) were obtained from [RuCl3(XPh3)2DMA]·DMA (DMA = dimethylacetamide) CH2Cl2/Et2O solution. The structures were characterized by X-ray diffraction studies. The complexes are formed from two Ru atoms bridged by three chloride anions. The two ruthenium atoms are also coordinated to two non-bridging Cl atoms and an AsPh3 or PPh3 ligand respectively. As an interesting feature, the cations of these complexes are protons, trapped in a very short hydrogen bond between two triphenylarsine or triphenylphosphine oxide molecules. 相似文献
128.
A novel electrophoretic BGE containing tungstate as complex-forming reagent is suitable for the separation of polyphenols. Similar to molybdate-containing BGE reported earlier (cf. M. Polásek, et al.., Talanta 2006, 69, 192) addition of tungstate to BGE affects significantly migration of compounds/ligands with vicinal -OH groups due to the formation of negatively charged complexes involving W(VI) as central ion. Baseline separation of mixtures of flavonoids (apigenin, luteolin, hyperoside, quercetin, and rutin) and phenolic acids (chlorogenic and p-coumaric acid) was achieved within 15 min with optimized BGE of pH 7.4 containing 50 mM N-(2-hydroxyethyl)piperazine-2'-(2-ethanesulfonic acid) (HEPES), 2.2 mM tungstate, and 25% v/v of methanol. The separation was performed in a 75 cm (effective length 42 cm)x 75 microm id uncoated fused-silica capillary at 30 kV with spectrophotometric detection at 275 nm. The calibration curves were rectilinear for 25-175 microg/mL of all analytes (cinnamic acid as the internal standard). The LODs ranged from 1.8 to 6 microg/mL for all analytes except for chlorogenic acid. Intraday precision (n = 6) of migration times (RSD < or = 1.2%) and peak areas (RSD < or = 5.6%) was evaluated. The tungstate-based BGEs can be alternatively utilized for the analysis of polyphenols at considerably lower pH than with conventional alkaline borate-based BGEs. 相似文献
129.
Claudia Rodrigues Alzir A. Batista Ricardo Q. Auclio Letícia R. Teixeira Lorenzo do Canto Visentin Heloisa Beraldo 《Polyhedron》2008,27(14):3061-3066
N4-Methyl-4-nitrobenzaldehyde thiosemicarbazone (H4NO2Fo4M), N4-methyl-4-nitrobenzophenone thiosemicarbazone (H4NO2Bz4M) and their ruthenium(II) complexes [Ru(4NO2Fo4M)2(PPh3)2] (1), [Ru(4NO2Bz4M)2(PPh3)2] (2), [Ru(4NO2Fo4M)2(dppb)] (3) and [Ru(4NO2Bz4M)2(dppb)] (4) (dppb = 1,4-bis(diphenylphospine)butane) were obtained and characterized. The crystal structure of H4NO2Fo4M has been determined. Electrochemical studies have shown that the nitro anion radical, one of the proposed intermediates in the mechanism of action of nitro-containing anti-trypanosomal drugs, is formed at approximately −1.00 V in the free thiosemicarbazones as well as in their corresponding ruthenium(II) complexes, suggesting their potential to act as antitrypanosomal drugs. The natural fluorescence of H4NO2Fo4M, H4NO2Bz4M and complexes (1)–(4) provides a way to identify and to monitor their concentration in biological systems. 相似文献
130.
A simple method is described for the determination of Cd, Cu, Mn, Ni, Pb and Zn in nails by using inductively coupled plasma mass spectrometry (ICP-MS) or electrothermal atomic absorption spectrometry (ETAAS). Prior to analysis, 10-20 mg of nail samples were accurately weighed into (15 mL) conical tubes. Then, 1 mL of 25% (w/v) tetramethylammonium hydroxide (TMAH) solution was added to the samples, incubated at room temperature overnight and then further diluted to 10 mL with 1% (v/v) HNO(3). After that, samples were directly analyzed. Rhodium was used as internal standard for ICP-MS analysis. Method detection limits (3 s, n=20) were 0.1, 3.0, 1.0, 4.5, 1.5, 5.0 ng g(-1) for Cd, Cu, Mn, Ni, Pb and Zn, respectively for ICP-MS, and 24, 26, 30, 143, 130 and 1000 ng g(-1), respectively for ETAAS. The key issue addressed here is the elimination of the acid digestion prior to analysis. Moreover, with the use of the proposed method there is a considerable improvement in the sample throughput comparing to the traditional methods using microwave-assisted acid sample digestion prior to analysis. For validation purposes, six ordinary nail samples were solubilized and then directly analyzed by ICP-MS and ETAAS, with no statistical difference between the two techniques at 95% level on applying the t-test. 相似文献