1H‐HRMAS NMR study of smoked Atlantic salmon (Salmo salar)

High‐resolution magic angle spinning (HRMAS) NMR spectroscopic data of smoked Atlantic salmon (Salmo salar) were fully assigned by combination of one‐ and two‐dimensional‐HRMAS experiments. Complete representative spectra, obtained after few minutes of analysis time, revealed a large number of minor and major compounds in the sample. The methodology is limited by the low sensitivity of NMR, and therefore HRMAS only enables the determination of the most relevant components. These were fatty acids (FAs), carbohydrates, nucleoside derivatives, osmolytes, amino acids, dipeptides and organic acids. For the first time, spectra were resolved sufficiently to allow semiquantitative determination in intact muscle of the highly polyunsaturated FA 22:6 ω‐3. Additionally, the feasibility of ¹H‐HRMAS NMR metabolite profiling was tested to identify some bioactive compounds during storage. This profiling was carried out by the non‐destructive and direct analysis (i.e. without requiring sample preparation and multiple step procedures) of intact salmon muscle. The proposed procedure can be applied to a large number of samples with high throughput due to the short time of analysis and quick evaluation of the data. Copyright © 2010 John Wiley & Sons, Ltd.     

Nitrogen Source Optimization for Cellulase Production by Penicillium funiculosum, using a Sequential Experimental Design Methodology and the Desirability Function

The present study aimed at maximizing cellulase production by Penicillium funiculosum using sequential experimental design methodology for optimizing the concentrations of nitrogen sources. Three sequential experimental designs were performed. The first and the second series of experiments consisted of a 2⁴ and a 2³ factorial designs, respectively, and in the third one, a central composite rotational design was used for better visualizing the optimum conditions. The following nitrogen sources were evaluated: urea, ammonium sulfate, peptone, and yeast extract. Peptone and ammonium sulfate were removed from the medium optimization since they did not present significant statistical effect on cellulase production. The optimal concentrations of urea and yeast extract predicted by the model were 0.97 and 0.36 g/L, respectively, which were validated experimentally. By the use of the desirability function, it was possible to maximize the three main enzyme activities simultaneously, which resulted in values for FPase of 227 U/L, for CMCase of 6,917 U/L, and for β-glucosidase of 1,375 U/L. These values corresponded to increases of 3.3-, 3.2-, and 6.7-folds, respectively, when compared to those obtained in the first experimental design. The results showed that the use of sequential experimental designs associated to the use of the desirability function can be used satisfactorily to maximize cellulase production by P. funiculosum.     

Photo-oxidative degradation mechanisms in styrene-ethylene-butadiene-styrene (SEBS) triblock copolymer

The photo-oxidative degradation of poly[styrene-b-ethylene-co-butylene-b-styrene], SEBS, has been studied at wavelengths cut-off below 290 nm, and monochromatic light of 254 nm and 365 nm, using a variety of spectroscopic methods including FTIR, UV and luminescence spectroscopy coupled with crosslinking and hydroperoxide analyses in order to understand the mechanisms involved. A study on polystyrene photodegradation is also compared at varying wavelengths in order to provide an understanding of the light sensitivity of the styrene vs the aliphatic phases in the SEBS. The increase in colour shows evidence for the presence of visible light absorbing chromophores. Hydroperoxide analysis reflects a rapid increase in the hydroperoxide concentration in the olefinic phase. Fluorescence spectroscopy shows a rapid disruption of the polystyrene excimers coupled with the formation of long-wavelength emitting polyconjugated stilbene-type chromophores. Phosphorescence analysis indicates the presence of acetophenone groups while GPC and sol/gel analysis showed that degradation occurs mainly due to chain scission. Changes in the FTIR spectra of the photo-oxidised samples show a predominant absorption associated with carboxylic acids and/or aliphatic esters at 1712 cm⁻¹. Other species such as hydroperoxides, ketones and α,β-unsaturated carbonyls are also formed and mechanisms are proposed.     

Alterations of plasma and cerebrospinal fluid glutamate levels in rats treated with the N-methyl-D-aspartate receptor antagonist, ketamine

It has been reported that the repeated administration of a sub-anesthetic dose of an N-methyl-D-aspartate receptor antagonist, ketamine, can produce an animal model of schizophrenia. Since no information is available on the alterations of the amino acid levels in ketamine-treated rats, we investigated the amino acid composition in the plasma and cerebrospinal fluid of rats that were repeatedly administered with ketamine for 5 consecutive days (30 mg/kg/day). The plasma and cerebrospinal fluid amino acid compositions in the fifth week after cessation of repeated ketamine administration were determined by highperformance liquid chromatography with fluorescence detection using a pre-column fluorescence reagent, i.e. 4-fluoro-7nitro-2,1,3-benzoxadiazole. Among the amino acids investigated in the present study, the level of plasma glutamic acid increased significantly (p < 0.05), while that of the cerebrospinal fluid glutamic acid decreased significantly in the ketamine-treated rats as compared with these levels in control rats injected with saline (p < 0.05, n = 7). These alterations in the glutamic acid level in the plasma and cerebrospinal fluid resemble those in schizophrenic patients, suggesting that ketamine-treated rats may be a useful model for performing research on the pathophysiology of schizophrenia.     

Molecular recognition: improved binding of biotin derivatives with synthetic receptors

NMR titrations and Monte Carlo conformational searches have been used to study the molecular recognition features of five urea derivatives with two synthetic hosts. We have improved the binding constant (Kb) values for all the studied guests and measured the largest binding constant of a complex involving a biotin derivative (biotin methyl ester) bound to a synthetic host by means of several interaction points and not only through the urea moiety.     

Host-guest chemistry of tolbutamide

The molecular recognition features of tolbutamide with four synthetic hosts have been studied by means of NMR titrations, NOESY experiments and Monte Carlo (MC) conformational search. The interaction strength and the most probable structure reveal new insights on the recognition phenomena of this urea derivative in comparison with close related compounds.     

Synthesis of benzofurazan derivatization reagents for carboxylic acids and its application to analysis of fatty acids in rat plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry

The derivatization regents for carboxylic acids, DAABD-AE (4-[2-(N,N-dimethylamino)ethylaminosulfonyl]7-(2-aminoethylamino)-2,1,3-benzoxadiazole), MePZBD-AE ([4-(4-N-methyl)piperazinosulfonyl]-7-(2-aminoethylamino)-2,1,3-benzoxadiazole) and APZBD-NHMe ([4-(4-N-aminoethyl)piperazinosulfonyl]-7-methylamino-2,1,3-benzoxadiazole) were developed for electrospray ionization-mass spectrometry (ESI-MS). The derivatization reaction with fatty acids was completed at 60 degrees C within 30 min. The derivatives of fatty acids were separated on a reversed-phase column and detected with ESI-MS. The detection limits attained for fatty acids were femtomol range and the calibration curves were linear over the range from 0.1 to 100 pmol (r2 > 0.992) for DAABD-AE and MePZBD-AE. DAABD-NHMe was applied to the analysis of fatty acids in rat plasma samples.     

The polarographic determination of traces of titanium-(IV) in the presence of n-benzoyl-n-phenylhydroxylamine

The polarographic behavior of the titanium(IV)-N-benzoyl-N-phenyl-hydroxylamine (BPHA) system in acidic medium and in water-ethanol mixtures has been studied. In (1+3) water-ethanol containing 2 M sulfuric acid and 0.05 M BPHA, titanium(IV) gives a single kinetically controlled wave. Titanium(IV) can be determined at concentrations as low as 5·10^-6M, in the presence of Fe(III), Cu(II), V(V), etc., but Cd(II), Sn(II and IV), As(V), U(VI) and Mo(VI) interfere.     

An automated analyzer for methylated arginines in rat plasma by high-performance liquid chromatography with post-column fluorescence reaction

A fully automated analyzer for methylated L-arginine metabolites [N,N-dimethyl-L-arginine (ADMA), N-methylarginine (NMMA) and N,N'-dimethyl-L-arginine (SDMA)] by high-performance liquid chromatography with post-column fluorescence derivatization was developed. This system consists of an on-line extraction, a separation on a reversed phase ion-pair chromatograph, a post-column derivatization by o-phthaladehyde (OPA) and thiol reaction, and fluorescence detection. NMMA, ADMA and SDMA were separated in 40 min with isocratic elution by a combination of octanoate and cyclohexane carboxylate as ion-pair reagents. The eluate was monitored at 450 nm with excitation at 337 nm. The calibration curves for NMMA, ADMA and SDMA showed linearity over the range from 0.05 micromol l(-1) (0.5 pmol on column) to 5.0 micromol l(-1) (50 pmol on column). This method does not require any time-consuming pre-treatment and requires only 10 microl of plasma sample for assay.     

A Mechanistic Overview of the Current Status and Future Challenges of Aluminum Anode and Electrolyte in Aluminum-Air Batteries

Aluminum-air batteries (AABs) are regarded as attractive candidates for usage as an electric vehicle power source due to their high theoretical energy density (8100 Wh kg⁻¹), which is considerably higher than that of lithium-ion batteries. However, AABs have several issues with commercial applications. In this review, we outline the difficulties and most recent developments in AABs technology, including electrolytes and aluminum anodes, as well as their mechanistic understanding. First, the impact of the Al anode and alloying on battery performance is discussed. Then we focus on the impact of electrolytes on battery performances. The possibility of enhancing electrochemical performances by adding inhibitors to electrolytes is also investigated. Additionally, the use of aqueous and non-aqueous electrolytes in AABs is also discussed. Finally, the challenges and potential future research areas for the advancement of AABs are suggested.