Demonstration of the optical limiting effect for an hemiporphyrazine

The hemiporphyrazine complex 9,22-bis(dibutoxy)hemiporphyrazinato chloroindium(III) (1) is one of the few examples for this class of compounds, which displays the nonlinear optical effect of reverse saturable absorption for nanosecond laser pulses in the visible spectrum. The high linear transmission combined with the fast switching into a strongly absorbing excited state in the same spectral range (400-650 nm), renders the studied hemiporphyrazine an ideal material for the passive shuttering of pulsed radiations.     

Validation of a gas chromatography/triple quadrupole mass spectrometry based method for the quantification of pesticides in food commodities

A new multiresidue method has been validated in cucumber matrix for the routine analysis of 130 multiclass pesticide residues by gas chromatography/triple quadrupole mass spectrometry. The pesticides were extracted with ethyl acetate. A first identification of the pesticides was based on a tandem mass spectrometric (MS/MS) screening method, which monitors a single transition for each target compound, in less than 12 min. After that, potentially non-negative samples were analyzed again by the MS/MS confirmation/quantification method, which monitors two or three MS/MS transitions for each compound, also in less than 12 min. Performance characteristics, such as trueness, precision, linear range, detection limit (LOD) and quantification limit (LOQ), for each pesticide were calculated. The average recoveries obtained ranged between 70 and 120% at three different fortification levels (25, 200 and 500 microg/kg) with precision, expressed as relative standard deviation (RSD), values lower than 15%. The calculated LOD and LOQ were typically <3.2 and 9.6 microg/kg, respectively. Such limits were much lower than the maximum residue levels (MRLs) established by European legislation. The proposed methodology was applied to the determination of pesticides in real vegetable samples from Almería (Spain).     

Monitoring the zinc affinity of the metallo-β-lactamase CphA by automated nanoESI-MS

Metallo-beta-lactamases are zinc containing enzymes that are able to hydrolyze and inactivate beta-lactam antibiotics. The subclass B2 enzyme CphA of Aeromonas hydrophila is a unique metallo-beta-lactamase because it degrades only carbapenems efficiently and is only active when it has one zinc ion bound. A zinc titration experiment was used to study the zinc affinity of the wild-type and of several mutant CphA enzymes. It shows that a second Zn(2+) is also bound at high ion concentrations. All samples were analyzed using mass spectrometry in combination with an automated nanoESI source. The metal-free enzyme has a bimodal charge distribution indicative of two conformational states. A completely folded enzyme is detected when the apo-enzyme has bound the first zinc. Intensity ratios of the different enzyme forms were used to deduce the zinc affinities. CphA enzymes mutated in metal ligands show decreased zinc affinity compared to wild-type, especially D120 mutants.     

Optimal treatments in cost-effectiveness analysis in the presence of covariates: Improving patient subgroup definition

In the presence of covariates, the cost-effectiveness analysis of medical treatments shows that the optimal treatment varies across the patient population subgroups, and hence to accurately define the subgroups is a crucial step in the analysis. A patient subgroup definition using only influential covariates within the potential set of patients covariates established by the expert has recently been proposed, and the influential covariates were chosen from the univariate distributions of the effectiveness and the cost, conditional on the effectiveness. In this paper, we argue that the Bayesian variable selection procedure should be developed using the bivariate distribution of the cost and the effectiveness, which is not the usual practice. This new approach, provides results with wider applicability and more understandable without a significative increase in the complexity of the procedure. For real and simulated data sets, optimal treatments for subgroups are found, and compared with that from previous methods.     

Experimental thermochemical study of the monochloronitrobenzene isomers

The standard (p^° = 0.1 MPa) molar enthalpies of formation of 2-, 3-, and 4-chloronitrobenzene isomers, in the crystalline state, at T = 298.15 K, were derived from the standard (p^° = 0.1 MPa) massic energies of combustion, in oxygen, at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of sublimation of the isomers, at T = 298.15 K, were obtained by high temperature Calvet microcalorimetry.     

896.

Experimental and computational thermochemical study of the dichloronitrobenzene isomers     

Manuel A.V. Ribeiro da Silva  Ana I.M.C. Lobo Ferreira  Ana Rita G. Moreno 《The Journal of chemical thermodynamics》2009,41(8):904-910

     

897.

In situ derivatization reaction and determination of ibuprofen in water samples using headspace generation-programmed temperature vaporization-gas chromatography-mass spectrometry     

José Luis Pérez Pavón  Ana María Casas FerreiraMaría Esther Fernández Laespada  Bernardo Moreno Cordero 《Journal of chromatography. A》2009,1216(39):6728-6734

The aim of the present work is to propose a method for the determination of ibuprofen, as a typical representative of pharmaceutical compounds, in aqueous samples. To do so, an in situ derivatization reaction in aqueous medium was employed in the vial of a headspace sampler (HS), after which instrumental measurements were made with gas chromatography-mass spectrometry (GC-MS). As the injection system we propose a programmed temperature vaporizer (PTV) where, in solvent vent mode, better results can be obtained than with the conventional split and splitless injection modes. Since the derivatization reaction takes place in the HS vial, after the mixing of reagents and the sealing of the vial, the whole process takes place on-line, with no need for intermediate steps. The simplicity and speed of the method – analysis throughput: 10.5 min – together with the limit of detection obtained (0.23 μg/L), bearing in mind that no preconcentration step or later clean-up step are required, make this a good method for the analysis of ibuprofen in aqueous samples of urban waste water.     

898.

Application of liquid chromatography–tandem mass spectrometry for the characterization of galactosylated and tagatosylated β-lactoglobulin peptides derived from in vitro gastrointestinal digestion     

Marta Corzo-Martínez  Rosa Lebrón-Aguilar  Mar Villamiel  Jesús Eduardo Quintanilla-López  F. Javier Moreno 《Journal of chromatography. A》2009,1216(43):7205-7212

This article describes a comprehensive characterization of bovine β-lactoglobulin peptides glycated with an aldohexose (galactose) or a ketohexose (tagatose), derived from in vitro gastrointestinal digestion, by liquid chromatography coupled to positive electrospray ion trap tandem mass spectrometry. In addition to the dissociation pathway previously described for aldohexoses-derived Amadori compounds, i.e. formation of the pyrylium ([M+H]⁺-54) and furylium ions ([M+H]⁺-84) via the oxonium ion ([M+H]⁺-18), another and more direct fragmentation route involving the formation of the imminium ion ([M+H]⁺-150) is also reported following extensive glycation rates of β-lactoglobulin with both carbohydrates. These results indicated that the analysis of digested proteins by LC-ESI-MS² on a three-dimensional ion trap monitoring neutral losses is an efficient and direct method to identify peptides glycated not only through the Amadori rearrangement but also via the Heyns rearrangement. Nevertheless, as the predominating MS² fragmentation pattern of the glycated peptides is derived from the sugar moiety, the sequence-informative b- and y-ions resulting from peptide backbone cleavage were undetected. To overcome this drawback, and taking advantage of multi-stage fragmentation capabilities of ion traps, the indicative Amadori and Heyns-derived imminium ions were successfully used in MS³ analyses to identify the peptide backbone, as well as the specific glycation site. In addition, further MS⁴ analyses were needed to carry out the characterization of doubly glycated peptides.     

899.

Microwave-assisted reactions of nitroheterocycles with dienes. Diels-Alder and tandem hetero Diels-Alder/[3,3] sigmatropic shift     

M. Victoria Gómez  Andrés Moreno  Abel de Cózar  Antonio de la Hoz  Pilar Prieto 《Tetrahedron》2009,65(27):5328-4001

Diels-Alder cycloaddition of 3-nitro-1-(p-toluenesulfonyl)indole 1 with dienes 2-6 under microwave irradiation in solvent-free conditions gave carbazole derivatives after elimination of the nitro group and in situ aromatization. While 3-nitro-1-(p-toluenesulfonyl)pyrrole 11 afforded indole derivatives, 4-nitro-1-(p-toluenesulfonyl)pyrazole 13 with cyclohexadiene 2 did not afford the expected cycloadduct but instead gave 1-cyclohexen-2-ylpyrazole 16. This process occurred by hydrolysis of the 1-(p-toluenesulfonyl) group, protonation of the diene and nucleophilic addition of the pyrazolate ion, as elucidated by computational studies. Reaction of nitroindole 1 with cyclohexadiene 2 afforded exclusively the endo stereoisomer (10endo) in a tandem hetero Diels-Alder/[3,3] sigmatropic shift, as determined by computational calculations.     

900.

Purification, Characterization, and Preliminary X-Ray Diffraction Analysis of a Lactose-Specific Lectin from Cymbosema roseum Seeds     

Rocha BA  Moreno FB  Delatorre P  Souza EP  Marinho ES  Benevides RG  Rustiguel JK  Souza LA  Nagano CS  Debray H  Sampaio AH  de Azevedo WF  Cavada BS 《Applied biochemistry and biotechnology》2009,152(3):383-393

The unique carbohydrate-binding property of lectins makes them invaluable tools in biomedical research. Here, we report the purification, partial primary structure, carbohydrate affinity characterization, crystallization, and preliminary X-ray diffraction analysis of a lactose-specific lectin from Cymbosema roseum seeds (CRLII). Isolation and purification of CRLII was performed by a single step using a Sepharose-4B-lactose affinity chromatography column. The carbohydrate affinity characterization was carried using assays for hemagglutination activity and inhibition. CRLII showed hemagglutinating activity toward rabbit erythrocytes. O-glycoproteins from mucine mucopolysaccharides showed the most potent inhibition capacity at a minimum concentration of 1.2 microg mL(-1). Protein sequencing by mass spectrometry was obtained by the digestion of CRLII with trypsin, Glu-C, and AspN. CRLII partial protein sequence exhibits 46% similarity with the ConA-like alpha chain precursor. Suitable protein crystals were obtained with the hanging-drop vapor-diffusion method with 8% ethylene glycol, 0.1 M Tris-HCl pH 8.5, and 11% PEG 8,000. The monoclinic crystals belong to space group P2(1) with unit cell parameters a = 49.4, b = 89.6, and c = 100.8 A.     

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In situ derivatization reaction and determination of ibuprofen in water samples using headspace generation-programmed temperature vaporization-gas chromatography-mass spectrometry

The aim of the present work is to propose a method for the determination of ibuprofen, as a typical representative of pharmaceutical compounds, in aqueous samples. To do so, an in situ derivatization reaction in aqueous medium was employed in the vial of a headspace sampler (HS), after which instrumental measurements were made with gas chromatography-mass spectrometry (GC-MS). As the injection system we propose a programmed temperature vaporizer (PTV) where, in solvent vent mode, better results can be obtained than with the conventional split and splitless injection modes. Since the derivatization reaction takes place in the HS vial, after the mixing of reagents and the sealing of the vial, the whole process takes place on-line, with no need for intermediate steps. The simplicity and speed of the method – analysis throughput: 10.5 min – together with the limit of detection obtained (0.23 μg/L), bearing in mind that no preconcentration step or later clean-up step are required, make this a good method for the analysis of ibuprofen in aqueous samples of urban waste water.     

Application of liquid chromatography–tandem mass spectrometry for the characterization of galactosylated and tagatosylated β-lactoglobulin peptides derived from in vitro gastrointestinal digestion

This article describes a comprehensive characterization of bovine β-lactoglobulin peptides glycated with an aldohexose (galactose) or a ketohexose (tagatose), derived from in vitro gastrointestinal digestion, by liquid chromatography coupled to positive electrospray ion trap tandem mass spectrometry. In addition to the dissociation pathway previously described for aldohexoses-derived Amadori compounds, i.e. formation of the pyrylium ([M+H]⁺-54) and furylium ions ([M+H]⁺-84) via the oxonium ion ([M+H]⁺-18), another and more direct fragmentation route involving the formation of the imminium ion ([M+H]⁺-150) is also reported following extensive glycation rates of β-lactoglobulin with both carbohydrates. These results indicated that the analysis of digested proteins by LC-ESI-MS² on a three-dimensional ion trap monitoring neutral losses is an efficient and direct method to identify peptides glycated not only through the Amadori rearrangement but also via the Heyns rearrangement. Nevertheless, as the predominating MS² fragmentation pattern of the glycated peptides is derived from the sugar moiety, the sequence-informative b- and y-ions resulting from peptide backbone cleavage were undetected. To overcome this drawback, and taking advantage of multi-stage fragmentation capabilities of ion traps, the indicative Amadori and Heyns-derived imminium ions were successfully used in MS³ analyses to identify the peptide backbone, as well as the specific glycation site. In addition, further MS⁴ analyses were needed to carry out the characterization of doubly glycated peptides.     

Microwave-assisted reactions of nitroheterocycles with dienes. Diels-Alder and tandem hetero Diels-Alder/[3,3] sigmatropic shift

Diels-Alder cycloaddition of 3-nitro-1-(p-toluenesulfonyl)indole 1 with dienes 2-6 under microwave irradiation in solvent-free conditions gave carbazole derivatives after elimination of the nitro group and in situ aromatization. While 3-nitro-1-(p-toluenesulfonyl)pyrrole 11 afforded indole derivatives, 4-nitro-1-(p-toluenesulfonyl)pyrazole 13 with cyclohexadiene 2 did not afford the expected cycloadduct but instead gave 1-cyclohexen-2-ylpyrazole 16. This process occurred by hydrolysis of the 1-(p-toluenesulfonyl) group, protonation of the diene and nucleophilic addition of the pyrazolate ion, as elucidated by computational studies. Reaction of nitroindole 1 with cyclohexadiene 2 afforded exclusively the endo stereoisomer (10endo) in a tandem hetero Diels-Alder/[3,3] sigmatropic shift, as determined by computational calculations.     

Purification, Characterization, and Preliminary X-Ray Diffraction Analysis of a Lactose-Specific Lectin from Cymbosema roseum Seeds

The unique carbohydrate-binding property of lectins makes them invaluable tools in biomedical research. Here, we report the purification, partial primary structure, carbohydrate affinity characterization, crystallization, and preliminary X-ray diffraction analysis of a lactose-specific lectin from Cymbosema roseum seeds (CRLII). Isolation and purification of CRLII was performed by a single step using a Sepharose-4B-lactose affinity chromatography column. The carbohydrate affinity characterization was carried using assays for hemagglutination activity and inhibition. CRLII showed hemagglutinating activity toward rabbit erythrocytes. O-glycoproteins from mucine mucopolysaccharides showed the most potent inhibition capacity at a minimum concentration of 1.2 microg mL(-1). Protein sequencing by mass spectrometry was obtained by the digestion of CRLII with trypsin, Glu-C, and AspN. CRLII partial protein sequence exhibits 46% similarity with the ConA-like alpha chain precursor. Suitable protein crystals were obtained with the hanging-drop vapor-diffusion method with 8% ethylene glycol, 0.1 M Tris-HCl pH 8.5, and 11% PEG 8,000. The monoclinic crystals belong to space group P2(1) with unit cell parameters a = 49.4, b = 89.6, and c = 100.8 A.