Preservative Effect of a Previous High-Pressure Treatment on the Chemical Changes Related to Quality Loss in Frozen Hake (<Emphasis Type="Italic">Merluccius merluccius</Emphasis>)

The objective of this study was the quality loss inhibition of hake (Merluccius merluccius) during the frozen storage. For it, the effect of a previous high-pressure (HP) treatment (150–450 MPa for 2 min) was analysed throughout a 5-month storage at ? 10 °C. Quality changes were monitored by complementary chemical analyses. Inhibition (p < 0.05) of dimethylamine (DMA), free fatty acid (FFA), formaldehyde (FA), trimethylamine, total volatile amine and fluorescent compound (tertiary lipid oxidation compound) formation was concluded by previous pressure treatment according to the one-way ANOVA analysis. On the contrary, no effect (p > 0.05) on the K value, polyene index and formation of peroxides and thiobarbituric acid reactive substances was achieved. Additionally, a multifactor ANOVA test (pressure and frozen storage time effects; i.e. comparison among HP treatments) showed an inhibitory effect (p < 0.015) on DMA and FFA formation, this effect increasing with pressure level applied. This inhibitory effect on the formation of such molecules related to quality loss can be explained on the basis of the damage caused to different kinds of enzymes such as trimethylamine oxide demethylase, lipases and phospholipases, so that their activity during the subsequent frozen storage would decrease. The work here presented provides for the first time information concerning the employment of HP technology to inhibit the DMA, FA and FFA formation during the frozen storage of hake. Further research focussed on commercial frozen conditions (? 18 °C) and including sensory and nutritional aspects is foreseen.     

Subjective perception of safety in healthy individuals working with 7 T MRI scanners: a retrospective multicenter survey

Objective

To retrospectively assess perception of safety of healthy individuals working with human 7 Tesla (T) magnetic resonance imaging (MRI) scanners.

Materials and methods

A total of 66 healthy individuals with a mean age of 31 ± 7 years participated in this retrospective multicentre survey study. Nonparametric correlation analysis was conducted to evaluate the relation between self-reported perception of safety and prevalence of sensory effects while working with 7 T MRI scanners for an average 47 months.

Results

The results indicated that 98.5 % of the study participants had a neutral or positive feeling about safety aspects at 7 T MRI scanners. 45.5 % reported that they feel very safe and none of the participants stated that they feel moderately or very unsafe while working with 7 T MRI scanners. Perception of safety was not affected by the number of hours per week spent in the vicinity of the 7 T MRI scanner or the duration of experience with 7 T MRI. More than 50 % of individuals experienced vertigo and metallic taste while working with 7 T MRI scanners. However, participants’ perceptions of safety were not affected by the prevalence of MR-related symptoms.

Conclusions

The overall data indicated an average perception of a moderately safe work environment. To our knowledge, this study delineates the first attempt to assess the subjective safety perception among 7 T MRI workers and suggests further investigations are indicated.

     

Analysis of chiral amino acids in conventional and transgenic maize

In this work, a new chiral micellar electrokinetic chromatography with laser-induced fluorescence detection (chiral-MEKC-LIF) method is proposed to identify and quantify D- and L-amino acids in three lines of transgenic maize and their corresponding nontransgenic parental lines grown under identical conditions. The optimized procedure includes amino acids extraction, derivatization with FITC and chiral-MEKC-LIF separation in a background electrolyte composed of 100 mM sodium tetraborate, 80 mM SDS, and 20 mM beta-CD at pH 10.0. The D- and L-forms of Arg, Ser, Ala, Glu, and Asp, corresponding to the majority amino acids usually found in maize, are separated in less than 25 min with efficiencies up to 890,000 plates/m and high sensitivity (i.e., LODs as low as 160 nM were obtained for D-Arg for a signal-to-noise ratio of three), allowing the detection of 1% D-Arg in the presence of 99% of its opposite enantiomer. Using this method, different D-amino acids are detected in all investigated maize samples providing the reproducible quantification of the D-enantiomeric excess (% d-aa) for each amino acid calculated as % D-aa = 100D-aa/(D-aa + L-aa). Thus, significant differences were observed among the % d-aa values for the different conventional varieties (Aristis, Tietar, and PR33P66 maize) as could be expected from their natural variability. More interestingly, comparing each conventional maize with its corresponding transgenic line, very similar % D-aa values were obtained for one of the studied maize couples (Tietar vs Tietar-Bt) what could be presented as a new proof of their substantial equivalence. However, significant differences in the % d-aa values were observed for the other lines of maize studied. It is concluded that enantioselective procedures can open new perspectives in the study of transgenic organisms in order to corroborate (or not) the equivalence with their conventional counterparts.     

Shall we dance? How a multicopper oxidase chooses its electron transfer partner

Multicopper oxidases (MCOs) are encoded in the genomes of Eukarya, Bacteria, and Archea. These proteins are unique in that they contain at least four Cu atom prosthetic groups organized into one each of the three spectral classifications of copper sites in biology: type 1 (T1), type 2 (T2), and binuclear type 3 (T3), where the T2 and T3 sites form a trinuclear Cu cluster. With these four redox-active copper sites, the multicopper oxidases catalyze the four-electron (4e(-)) reduction of dioxygen to 2H2O, an activity that they alone share with the terminal heme-containing oxidases. Most MCOs exhibit broad specificity towards organic reductants, while a relatively small number of family members exhibit equally robust activity towards metal ions like Fe(II), Cu(I), and Mn(II) and, thus, are considered metallo-oxidases. This Account analyzes the structure-activity features of multicopper oxidases that determine their relative substrate specificity. Since the substrate oxidation step involves an outer-sphere electron transfer from the reductant to the T1Cu site in the protein, the concepts of Marcus theory are applied to unravel the origin of the substrate specificity of the multicopper ferroxidases.     

Spatio-temporal modeling of perimetric test data

This work describes the application of a spatio-temporal modeling to the study of glaucoma, a very serious ocular illness. The aim of this modeling is to solve various significant medical problems, namely the forecasting of future observations, the classification of observations as normal or defective, and the simulation of new longitudinal data sets. In order to ascertain whether a patient suffers from glaucoma, a perimetry is performed. The output of a perimetry is called a visual field and consists of a map with 52 numerical values plotted on a regular grid. In this work, a data set of healthy patients' visual fields is used. The work begins with an exploratory spatial data analysis. A semi-parametric approach is used to model the mean, and the variogram is fitted using a Matérn function. Once the spatial structure has been analysed, the spatial mean is subtracted from all the observations in the data set and the spatio-temporal correlation of the residuals is explored. All this information is used to build a space-time model, the parameters of which are estimated by maximum likelihood. Different methods are used to check the goodness of fit.     

The classification of almonds (Prunus dulcis) by country and variety using UHPLC-HRMS-based untargeted metabolomics

The aim of this study was to use an untargeted UHPLC-HRMS-based metabolomics approach allowing discrimination between almonds based on their origin and variety. Samples were homogenised, extracted with ACN:H₂O (80:20) containing 0.1% HCOOH and injected in a UHPLC-QTOF instrument in both positive and negative ionisation modes. Principal component analysis (PCA) was performed to ensure the absence of outliers. Partial least squares – discriminant analysis (PLS-DA) was employed to create and validate the models for country (with five different compounds) and variety (with 20 features), showing more than 95% accuracy. Additional samples were injected and the model was evaluated with blind samples, with more than 95% of samples being correctly classified using both models. MS/MS experiments were carried out to tentatively elucidate the highlighted marker compounds (pyranosides, peptides or amino acids, among others). This study has shown the potential of high-resolution mass spectrometry to perform and validate classification models, also providing information concerning the identification of the unexpected biomarkers which showed the highest discriminant power.     

Screening of mycotoxin multicontamination in medicinal and aromatic herbs sampled in Spain

BACKGROUND: The aim of this study was to screen the multicontamination by mycotoxins in a wide variety of aromatic and/or medicinal herb samples collected in Spain. Mycotoxins studied were aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), T‐2 toxin (T‐2), citrinin and fumonisins (FBs). Mycotoxins were analysed by ELISA after a clean‐up step with multifunctional columns (AFs, ZEA, DON, FBs and T‐2) or polyamide column (citrinin). RESULTS: Of the 84 samples analysed 99% were contaminated with T‐2, 98% with ZEA, 96% with AFs, 63% with OTA, 62% with DON, 61% with citrinin and 13% with FBs. Nearly 87% of samples contained four or more mycotoxins simultaneously, being AFs, T‐2 and ZEA the mycotoxins co‐existing in almost every sample. 100% of the samples in our study were multicontaminated. CONCLUSION: This study shows that this kind of commodity could be an important source of mycotoxin contamination and, in general, this contamination is not limited to only one group of mycotoxins. Mycotoxin contamination on artichoke immature florets, boldus leaves, burdock leaves, dandelion plant, frangula bark, ginkgo leaves, lemon verbena leaves, olive leaves, red tea leaves, ribgrass leaves, St Mary's thistle seeds, spearmint leaves, star anise fruit, vervain and white tea leaves has been described for the first time. Finally, this is the first report on DON and T‐2 presence in herbs. No study of this kind has been previously developed in Spain. Copyright © 2009 Society of Chemical Industry     

New hydrogels based on maleilated collagen with potential applications in tissue engineering

New hydrogels based on maleic anhydride (MA) modified collagen were prepared with the aim of overcoming the high degradation rate displayed by collagen that is not otherwise chemically crosslinked. Semi-interpenetrated matrices were obtained by free radical polymerization of maleilated collagen (CM) and 2-hydroxyethyl methacrylate (HEMA) in the presence of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) as initiating system. The resulting matrices (CMH) had a sharp decrease in degradation, when compared to pure collagen. FTIR and H¹ NMR spectroscopies were used to confirm the incorporation of MA on the collagen peptide chains. The final composition of CMH was found to be strongly dependent by the concentration of maleilated collagen. The morphology of the hydrogels was studied by Scanning electron microscopy (SEM) and the macro-gel structure was confirmed. Water uptake of the synthetised hydrogels is influenced by both composition and the porosity of the matrices.     

Evaluation of the controlled release ability from the poly(2-hydroxyethyl methacrylate-co-3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane) polymer network synthesized in the presence of β-cyclodextrin

The study presents the possibility to use the 2-hydroxyethyl methacrylate--HEMA copolymer with a comonomer with spiroacetal moiety, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane)-U, as polymer network for loading the indomethacin--INN as drug model, and also, the controlled release evaluation of the prepared bioactive system. The macromolecular compounds were prepared by radical dispersion polymerization in the presence of a pair of surfactants. The use of cyclodextrin as surfactant allowed the building of the host-guest complexes by inclusion of hydrophobic molecules. Also, the cyclodextrin supplemented the hydrogen bonds and the hydrophobic interactions responsible for the stability of the achieved complexes. The copolymers composition and the INN inclusion onto the polymeric matrix were confirmed by FTIR analysis. The porous structure of the lyophilized P(HEMA-U) samples was illustrated by SEM images. The swelling studies evidenced the interdependence between P(HEMA-U) network properties and the spiroacetal moiety amount. Thus, the copolymers presented the increase of the equilibrium swelling degree with pH and temperature. Also, the polymeric matrices manifested dual sensitivity with pH and temperature. The in vitro release of the INN drug from the polymeric network as well as the in vivo experimental studies evidenced the benefit consequence of the spiroacetal compound presence. The clinical observation of the experimental groups does not show any behavioral modifications to suggest a possible toxic effect of these polymeric formulations with and without INN.     

Thermal stability of Ln2NiO4+δ (Ln: La, Pr, Nd) and their chemical compatibility with YSZ and CGO solid electrolytes

Thermal stability and chemical compatibility with electrolyte materials for Solid Oxide Fuel Cells (SOFC) have been studied on Ruddlesden-Popper nickelates Ln₂NiO_4+δ with Ln: La, Pr and Nd. Samples of each composition prepared by three different routes, were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Different microstructures were achieved by each preparation method. The thermal stability of these compounds was analyzed by annealing all the samples at 700 and 900 °C in air. Pr₂NiO_4+δ (PNO) decomposes after 24 h of annealing at 700 °C confirming its instability at these conditions. Evidences of chemical reaction between La₂NiO_4+δ (LNO) and both Ce_0.9Gd_0.1O_1.96 (CGO) and Zr_0.92Y_0.08O_1.96 (YSZ) were observed at 700 and 900 °C, respectively. No decomposition or chemical reaction with YSZ or CGO were found for Nd₂NiO_4+δ (NNO) below 900 °C. Nevertheless, reactivity with both electrolytes was found for this compound at 1000 °C. The kinetics of these reactions strongly depends on the microstructure of Ln₂NiO_4+δ.