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151.
Cleide M. F. Soares Onelia A. dos Santos Heizir F. de Castro Flavio F. de Moraes Gisella M. Zanin 《Applied biochemistry and biotechnology》2004,113(1-3):307-319
The hydrolysis of tetraethoxysilane using the sol-gel process was used to produce silica matrices, and these were tested for the immobilization of lipase from Candida rugosa by three methods: physical adsorption, covalent binding, and gel entrapment in the presence and absence of polyethylene glycol (PEG-1450). The silica matrices and their derivatives were characterized regarding particle size distribution, specific surface area, pore size distribution (Brunauer, Emmett, and Teller [B.E.T.] method), yield of grafting (thermogravimetric analyzer [TGA]), and chemical composition (Fourier transform infrared). Immobilization yields based on recovered lipase activity varied from 3.0 to 32.0%, and the highest efficiency was attained when lipase was encapsulated in the presence of PEG. 相似文献
152.
Patricia Kaori Soares Gustavo Galo Marcheafave Adriano de Araújo Gomes Ieda Spacino Scarminio Roy Edward Bruns 《Chromatographia》2018,81(8):1189-1200
HPLC-DAD analysis of statistical mixture design extracts of Erythrina speciosa Andrews leaves provided chromatographic and UV–visible profiles of their basic and organic fractions that were treated with the PARAFAC multivariate method. The design extracts provided greater varieties and amounts of metabolites than could be obtained by classical extraction methods. Fractionation provided more diverse fingerprint information than obtained previously from only the crude extract. The two largest chromatographic peaks, one with a 4.8 min elution time having an intense spectral band at 235 nm and the other a 5.8 min peak with an intense 238 nm band for the basic fraction were obtained with the ternary 1:1:1 ethanol–dichloromethane–hexane mixture. These can be assigned to diene-type and lactonic alkaloids. Peaks with the same retention times are also found in the organic fraction but are extracted with different mixtures and have distinct spectral behavior in the 235 nm region, probably being aromatic alkaloids. The above strategy permits a more unambiguous assignment of metabolic groups to specific chromatographic peaks. This can be expected to provide higher quality chromatographic fingerprints for natural products’ chemistry. 相似文献
153.
154.
Pinho e Melo TM Soares MI Gonsalves AM Paixão JA Beja AM Silva MR 《The Journal of organic chemistry》2005,70(17):6629-6638
1-Azafulvenium methides, generated from pyrrolo[1,2-c]thiazole-2,2-dioxides' thermal extrusion of sulfur dioxide, led to the synthesis of functionalized pyrroles. The intramolecular trapping of these transient 8pi 1,7-dipoles in pericyclic reactions, namely sigmatropic [1,8]H shifts and 1,7-electrocyclization, allowed the synthesis of N-vinylpyrroles and C-vinylpyrroles which, under flash vacuum pyrolysis conditions, are converted into 5-oxo-5H-pyrrolizines or 4-oxo-1,4-dihydro-1-aza-benzo[f]azulenes, respectively. These heterocycles can also be obtained directly from FVP of pyrrolo[1,2-c]thiazole 2,2-dioxides. The synthesis and X-ray structure of a new 6-oxocyclopenta[b]pyrrole derivative is also reported. 相似文献
155.
The influence of [(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)amino]-1-propanesulfonic acid (TAPS) on solutions containing lead(II) was studied by direct current polarography (DCP) and glass electrode potentiometry (GEP). The readings were taken at fixed total TAPS to total lead(II) concentration ratios and various pH values, at 25.0 ± 0.1 °C and ionic strength 0.1 M KNO3.Due to the basic pKa of the ligand, which occurs in the pH range where large amount of lead polynuclear species are formed, and the occurrence of ligand adsorption, that disabled the use of high concentrations of TAPS on DCP experiments, GEP and DCP experimental conditions were put to the limit in order to provide the correct Pb-TAPS-OH model and reliable stability constants.The proposed final model is: PbL, PbL2, PbL2(OH) and PbL2(OH)2 with overall stability constants values, as log β, 3.27 ± 0.06, 6.5 ± 0.1, 12.7 ± 0.1 and 17.27 ± 0.06, respectively.A comparative analysis of the strength of complexation of TAPS and a structural related buffer, 2-hydroxy-3-[tris(hydroxymethyl)methylamino]-1-propanesulfonic acid (TAPSO), with lead is also discussed. 相似文献
156.
CarinaM.M. Machado Ignacy Cukrowski HelenaM.V.M. Soares 《Helvetica chimica acta》2003,86(10):3288-3304
The influence of 2‐hydroxy‐3‐[(2‐hydroxy‐1,1‐dimethylethyl)amino]propane‐1‐sulfonic acid (AMPSO=HL) on systems containing copper(II) was studied by glass‐electrode potentiometry (GEP) and direct‐current polarography (DCP), at fixed total‐ligand‐to‐total‐metal‐concentration ratios and various pH values (25°, 0.1M KNO3 medium). The predicted model ([CuL]+, [CuL(OH)], [CuL2], [CuL2(OH)]?, [CuL2(OH)2]2?, and [CuL3]?) and the overall stability constants for species found were obtained by combining results from both electrochemical techniques. The last five complexes are reported for the first time. For the species [CuL]+, [CuL2], [CuL3]?, and [CuL2(OH)2]2?, it was possible to determine stability constants with reasonable certainty and their values, as log β, were found to be 4.62±0.04, 9.5±0.1, 13.4±0.1, and 21.2±0.1, respectively. For the species [CuL(OH)] and [CuL2(OH)]?, stability constants 11.7±0.2 and 15.6±0.2, respectively, are presented as indicative values. It was demonstrated that AMPSO buffer may decrease the Cu2+ concentration by ten orders of magnitude by forming complexes with Cu2+. For the first time, the correction in DCP waves for the adsorption of the ligand and quasi‐reversibility of the metal allowed to determine stability‐constant values that are in good agreement with the values obtained by GEP. The importance of graphic analysis of data and significance of employing two analytical techniques was demonstrated; neither GEP nor DCP would be able to provide the correct M/L/OH? model and reliable stability constants when used independently. 相似文献
157.
Azafulvenium methides generated by the thermal extrusion of SO2 from 1-methyl- and 1,1-dimethyl-1H,3H-pyrrolo[1,2-c]thiazole-2,2-dioxides undergo [1,8]H sigmatropic shifts to give vinylpyrroles. Flash vacuum pyrolysis of the C-vinylpyrroles affords 5-oxo-5H-pyrrolizines or C-allyl-1H-pyrroles. 相似文献
158.
M. Teresa Vasconcelos M. Fernanda C. Leal Helena M. V. M. Soares 《Analytica chimica acta》1996,330(2-3):273-281
The influence of the ratio Cu : L on the lability of copper(II) complexes with simple ligands of different thermodynamic stabilities (L=EDTA, NTA, cysteine, proline or glycine) was investigated in the range 4:1–1:3. Chelex-100 and chitin were used parallel and batch wise, to cause the dissociation of the complexes, and the results were compared. A few experiments were also performed with the yeast, Saccharomyces cerevisiae. The effect of the exposure time, between 5 and 30 min, and mass (or number of sites) of the particulate matter (PM), always in large excess, were also studied. For all systems, but Cucysteine with chitin, the lability of CuL showed no marked dependence on the mass of PM: when the mass of PM was duplicated, an increase in lability by ≤ 10% was found. For cysteine and proline with Chelex-100, and cysteine and glycine with chitin, the lability of Cu---L complexes markedly increased with the time of exposure, which indicated that the kinetics of the substitution reactions were relatively slow. These results indicate the role of both the leaving and entering ligands in the kinetics of the ligand substitution reactions. The effect of Cu : L on the complex dissociation was more marked with chitin than with Chelex-100. When the leaving ligand is in excess (Cu : L < 1) the magnitude of that excess did not affect markedly the lability. But, when Cu : L> 1, the lability decreased with the increase of the excess of metal for cysteine or glycine with Chelex-100, and for all ligands in presence of chitin. The heterogenous behaviour of the PM may be partially responsible for these results. A maximum lability was observed for 1:1 ratio, particularly for the complexes that are thermodynamically more stable. In the presence of yeast cells, the tendencies mentioned above were confirmed. The present results reinforce the operational character of the speciation studies based on lability data, and that relationship between lability and bioavailability must be analysed for each individual case and should not be extrapolated to different PM or experimental conditions. 相似文献
159.
Perspectives on bioenergy and biotechnology in Brazil 总被引:4,自引:0,他引:4
Adalberto Pessoa-Jr Inêes Conceição Roberto Marcelo Menossi Raphael Revert dos Santos Sylvio Ortega Filho Thereza Christina Vessoni Penna 《Applied biochemistry and biotechnology》2005,121(1-3):59-70
Brazil is one of the world’s largest producers of alcohol from biomass at low cost and is responsible for more than 1 million
direct jobs. In 1973, the Brazilian Program of Alcohol (Proalcool) stimulated the creation of a bioethanol industry that has
led to large economic, social, and scientific improvements. In the year 1984, 94.5% of Brazil’s cars used bioethanol as fuel.
In 2003/2004, 350.3 million of sugarcane produced 24.2 million t of sugar and 14.4 billion L of ethanol for an average 4.3
million cars using ethanol. Since its inception, cumulative investment in Proalcool totals US$11 billion, and Brazil has saved
US$27 billion in oil imports. The ethanol production industry from sugarcane generates 152 times more jobs than would have
been the case if the same amount of fuel was produced from petroleum, and the use of ethanol as a fuel is advantageous for
environmental reasons. In 2003, one of the biggest Brazilian ethanol industries started consuming 50% of the residual sugarcane
bagasse to produce electrical energy (60 MW), a new alternative use of bioenergy for the Brazilian market. Other technologies
for commercial uses of bagasse are in development, such as in the production of natural fibers, sweeteners (glucose and xylitol),
single-cell proteins, lactic acid, microbial enzymes, and many other products based on fermentations (submerged and semisolid).
Furthermore, studies aimed at the increase in the biosynthesis of sucrose and, consequently, ethanol productivity are being
conducted to understand the genetics of sugarcane. Although, at present, there remain technical obstacles to the economic
use of some ethanol industry residues, several research projects have been carried out and useful data generated. Efficient
utilization of ethanol industry residues has created new opportunities for new value-added products, especially in Brazil,
where they are produced in high quantities. 相似文献
160.
Penna Thereza Christina Vessoni Ishii Marina Machoshvili Irene Alexeevna Marques Marcelo 《Applied biochemistry and biotechnology》2002,98(1-9):525-538
Paper strips inoculated with spores of Bacillus stearothermophilus ATCC 7953 were conventionally dried (lot 1) and lyophilized (lot 2); stored in defined environments of 32 and 86% relative
humidity at 10, 25 and 33°C for 210 d; and submitted to moist heat treatments at 121°C. A significant decrease in thermal
resistance from initial starting levels was found for lyophilized bioindicators stored at 86% relative humidity. The respective
average D
121°C values were 1.55 ± 0.05 and 1.37 ± 0.10 min for lyophilized bioindicators stored at 32 and 86% relative humidity; and 1.65±0.15min
and 1.57 ± 0.11 min for dried bioindicators stored in the same environments. 相似文献