Evidence of competitive mechanisms during oxidation of CS(2)N(-)(3) by permanganate ion in alkaline solution

The oxidation of the 1,2,3,4-thiatriazole-5-thiolate ion, CS(2)N(-)(3), by permanganate ions in alkaline medium has been investigated over a wide range of oxidant concentrations. With a moderate excess of permanganate ion a 17-electron reaction takes place, yielding sulphate, nitrogen and carbon dioxide. With a high permanganate concentration the pseudohalide undergoes a 26-electron reaction yielding sulphate, carbon dioxide and nitrite as final products. These two different stoichiometries arise from the existence of competitive mechanisms and the ratio C(MnO(-)(4))/C(CS(2)N(-)(3)) will determine the course of the reaction.     

Assessing the separation of neutral plant secondary metabolites by micellar electrokinetic chromatography

In this work, partition coefficients (Pwm) and solute-micelle association constants per monomer (Km/N) were measured using micellar electrokinetic chromatography in tetraborate-sodium dodecylsulfate electrolytes for 18 important plant secondary metabolites (coumarin, verbenone, camphor, eucalyptol, carvone, alpha-terpineol, linalool, jasmone, bergapten, rose oxide, geraniol, t-anethole, citronellal, citronellol, p-cymene, limonene, caryophyllene and nerol) of wide occurrence in herbal extracts and essential oils. Caryophyllene presented a retention time longer than anthracene (micelle marker) and its set of constants could not be determined accurately. Pwm and Km/N were generated by the non-linear data fitting of both partition and solute-micelle association models for the 17 solutes under consideration (caryophyllene excluded). Pwm varied from 147 (coumarin) to 13175 (limonene) while Km/N varied from 37 (coumarin) to 3721 (limonene). Under optimal conditions, the separation of the selected compounds was attempted successfully in commercialized samples of rose, anise and geranium essential oils.     

Direct sampling tandem mass spectrometry (MS/MS) and multiway calibration for isomer quantitation

Direct sampling tandem mass spectrometry (MS/MS) was used for the quantitation of mixtures of the isomers 2-, 3- and 4-ethyl pyridine. The similarity between the analytes and the second-order nature of MS/MS data require the use of multivariate calibration techniques capable of handling multiway data. Multilinear PLS (N-PLS) was applied here, as well as the alternative technique of unfolding the data and using standard two-way PLS. Particular attention was paid to the optimal type of spectral preprocessing. Due to the presence of heteroscedastic noise the logarithmic transform of the spectra prior to calibration gives the best results. Predictions errors of the order of 10-15% were obtained, which compare well with other results found in the literature.     

Evaluation of supports and methods for immobilization of enzyme cyclodextringlycosyltransferase

An experimental design with factorial planning was used for the immobilization of the enzyme cyclodextringlycosyltransferase (CGTase) from Bacillus firmus (strain no.37) to select the best combination of support, method of immobilization, and conditions that gives primarily higher average values for the specific immobilized enzyme activity, and secondarily, higher average values for the percentage of protein fixation. The experimental design factors were as follows: supports—controlled-pore silica, chitosan, and alumina; immobilization methods—adsorption, and two covalent bonding methods, either with γ-aminopropyltriethoxysilane or hexamethylenediamine (HEMDA); conditions—7°C without agitation and 26°C with stirring. The best combination of factors that lead to higher average values of the response variables was obtained with immobilization of CGTase in silica with HEMDA at 7°C. However, immobilization in chitosan at 7°C gave the highest immobilized CGTase specific activity, 0.25 μmole of β-CD/(min·mg protein). Physical adsorption gave low specific enzyme activities, and, in general, a high load of enzyme leads to lower specific enzyme activity.     

Scale inhibition study by turbidity measurement

The concept of a critical supersaturation ratio (CSSR) has been used to characterize the effectiveness of different types of scale inhibitors, inhibitor concentration, and precipitating solution pH in order to prevent the formation of barium sulfate scale. The scale inhibitors used in this work were aminotrimethylene phosphonic acid (ATMP), diethylenetriaminepentamethylene phosphonic acid (DTPMP), and phosphinopolycarboxylic acid polymer (PPCA). The CSSR at which barium sulfate precipitates was obtained as a function of time for different precipitation conditions and was used as an index to evaluate the effect of the precipitation conditions. The results showed that the CSSRs decrease with increasing elapsed time after mixing the precipitating solutions, but increases with increasing scale inhibitor concentration and solution pH. The CSSR varies linearly with the log of the scale inhibitor concentration and with the precipitating solution pH. A SEM analysis showed that the higher the scale inhibitor concentration and solution pH, the smaller and more spherical the BaSO4 precipitates. Analysis of the particle size distribution revealed that increasing the elapsed time, the scale inhibitor concentration, and precipitating solution pH, all produce a broader particle size distribution and a smaller mean diameter of the BaSO4 precipitates. DTPMP and PPCA were the most effective BaSO4 scale inhibitors per ionizable proton and the most effective on a concentration basis, respectively.     

Production of an antiproliferative furanoheliangolide by Lychnophora ericoides cell culture

This work reports for the first time the production a furanoheliangolide (goyazensolide) by plant cell culture. Monitoring of the goyazensolide metabolism revealed that the maximum production occurred during the lag phase of the Lychnophora ericoides callus culture. The antiproliferative activity of obtained goyazensolide was evaluated against seven cancer cell lines using MTT assay. The results revealed a potent cytotoxic activity for the furaheliangolide with IC50 values in the range of 0.06 microg/ml for CEM leukemia cells to 0.75 microg/ml for B16 melanome cells.     

Production of the Enzyme Cyclodextringlycosyltransferase from Bacillus firmus Alkalophilic

Different culture media have been testedfor the production of the enzyme CGTase (cyclodextringlycosyltransferase) from Bacillus firmus (strain #37). The concentration of different carbon and nitrogen sources have been varied and the enzyme activity, cell concentration, reducing sugars, total reducing sugars, soluble protein and pH have been followed during cultivation. Results indicate that higher concentrations of yeast extract and polypeptone lead to increased synthesis of CGTase, whereas when starch is substituted by glucose there is a drastic inhibition of CGTase production.