A Comparative Study of the Analysis of Antioxidant Activities of Liquid Foods Employing Spectrophotometric, Fluorometric, and Chemiluminescent Methods

The antioxidant profile of liquid foods is complex and includes different lipid and water-soluble compounds. These should be considered when assessing total antioxidant capacity (TAC) of these beverages, since it may act synergistically rather than individually. This study describes and compares the use of spectrophotometric methods (Trolox equivalent antioxidant capacity, TEAC and 2,2-diphenyl-1-picrylhydrazyl, DPPH), fluorometric (oxygen radical antioxidant capacity, ORAC), and photochemiluminescence (PCL) for the measurement of the TAC of different liquid foods (fruit juice mixed with milk and vegetables beverage). An evaluation was also made for the influence of certain compounds (ascorbic acid, phenolic compounds, total carotenoids, and tocopherols) with antioxidant capacity that was present in the samples studied. The different methods studied allow the determination of the TAC of the analyzed foods in a precise and accurate way. The TAC values in the studied samples differ from the applied method. An overall antioxidant potency composite index was calculated by assigning each test's equal weight. When an index score was applied, ORAC method had the higher antioxidant capacity values in the analyzed liquid foods in comparison with the other methods. The correlations among the different methods used for the determination of the antioxidant capacity depend on food, that is, mainly due to compounds (lipid and water soluble) of the different food matrix. In addition, ascorbic acid was the main contributor to antioxidant capacity of fruit juice mixed with milk beverages measured with the different methods. However, in vegetables beverages, phenolic compounds were found to correlate more significantly with antioxidant capacity values.     

Stress and reconstruction on (0 0 1) transition-metal surfaces

We investigate the role of surface stress in the hex reconstruction of (0 0 1) transition-metal surfaces introducing the density-functional-theory stress density, a theoretical tool allowing the local analysis of the stress. By ab initio total energy, stress, and stress density calculations for Ir (0 0 1) we show that the reconstruction is due to the concurrence of tensile stress relief in the surface layer and the huge outward relaxation thereof. The latter causes a compressive stress relief in the region between the surface layer and the substrate, leading to an increased total surface stress.     

Applying Topological and Economical Principles in Catalyst Design: New Alumina–Cobalt Core–Shell Catalysts

Designing new and effective catalysts may be an art, but its consequences are very real and pragmatic. That said, chemists often build designs on ideal systems, whereas the manufacturing of chemicals requires catalysts that withstand varied feeds, harsh conditions and long exposure times. Moreover, economical considerations are often underestimated at the catalyst design stage. Here we discuss the inclusion of economical and topological considerations early on in the catalyst design process, giving as an example the synthesis and testing of a new type of alumina/cobalt Fischer–Tropsch catalysts.

     

Uncovering excellence in academic rankings: a closer look at the Shanghai ranking

In this paper, we examine whether the quality of academic research can be accurately captured by a single aggregated measure such as a ranking. With Shanghai University’s Academic Ranking of World Universities as the basis for our study, we use robust principal component analysis to uncover the underlying factors measured by this ranking. Based on a sample containing the top 150 ranked universities, we find evidence that, for the majority of these institutions, the Shanghai rankings reflect not one but in fact two different and uncorrelated aspects of academic research: overall research output and top-notch researchers. Consequently, the relative weight placed upon these two factors determines to a large extent the final ranking.     

NY‐ESO‐1 protein glycosylated by yeast induces enhanced immune responses

Vaccine strategies that target dendritic cells to elicit potent cellular immunity are the subject of intense research. Here we report that the genetically engineered yeast Saccharomyces cerevisiae, expressing the full‐length tumour‐associated antigen NY‐ESO‐1, is a versatile host for protein production. Exposing dendritic cells (DCs) to soluble NY‐ESO‐1 protein linked to the yeast a‐agglutinin 2 protein (Aga2p) protein resulted in protein uptake, processing and MHC class I cross‐presentation of NY‐ESO‐1‐derived peptides. The process of antigen uptake and cross‐presentation was dependent on the glycosylation pattern of NY‐ESO‐1‐Aga2p protein and the presence of accessible mannose receptors. In addition, NY‐ESO‐1‐Aga2p protein uptake by dendritic cells resulted in recognition by HLA‐DP4 NY‐ESO‐1‐specific CD4⁺ T cells, indicating MHC class II presentation. Finally, vaccination of mice with yeast‐derived NY‐ESO‐1‐Aga2p protein led to an enhanced humoral and cellular immune response, when compared to the bacterially expressed NY‐ESO‐1 protein. Together, these data demonstrate that yeast‐derived full‐length NY‐ESO‐1‐Aga2p protein is processed and presented efficiently by MHC class I and II complexes and warrants clinical trials to determine the potential value of S. cerevisiae as a host for cancer vaccine development. Copyright © 2010 John Wiley & Sons, Ltd.     

Screening of catalysts for H2S abatement from biogas to feed molten carbonate fuel cells

Different catalysts vanadium-based supported on mixed oxide (CeO₂, TiO₂, CuFe₂O₄) were prepared, characterized and tested for the partial selective oxidation of H₂S at low temperature.     

An evaluation of the application of a TiO2/ Cu(II)/solar simulated radiation system for selective oxidation of benzyl alcohol derivatives

BACKGROUND: The conversion of hydroxybenzyl alcohols, nitro‐benzyl alcohol and methoxybenzyl alcohols into the corresponding aldehydes is attempted in aqueous solution by Cu(II) (which reduces to Cu(0)), at room temperature, under acidic and deaerated conditions, using TiO₂ solar simulated light photocatalysis. RESULTS: Under the experimental conditions adopted, the yields of the corresponding hydroxyaldehydes, when Cu(II) was completely reduced to Cu(0), were 21.6% for 4‐hydroxybenzaldehyde, 11.5% for 3‐hydroxybenzaldehyde and 20.2% for 2‐hydroxybenzaldehyde. Higher conversions of 2‐methoxybenzyl alcohol and 4‐methoxybenzyl alcohol were recorded relative to unsubstituted benzyl alcohol. A selectivity of 5.2%, at 50% conversion of the substrate, was observed for the oxidation of 4‐nitrobenzyl alcohol to 4‐nitrobenzaldehyde. For high degrees of aromatic alcohols conversion, oxidation of the generated aldehydes to the corresponding benzoic acid derivatives is observed. CONCLUSION: The introduction of substituents into the aromatic alcohols structure changes the photocatalytic oxidation rate and product selectivities with respect to that previously observed for unsubstituted benzyl alcohol. In particular, the presence of both electron donating (hydroxy, methoxy groups) and electron withdrawing (nitrogroup) groups on the aromatic ring of the substrate causes a detrimental effect on the selectivity of the process with respect to the case of benzyl alcohol. © 2012 Society of Chemical Industry