Egg white lysozyme purification with a chitin–silica-based affinity chromatographic matrix

A composite biosorbent retaining non-covalently bound chitin in between layers of a silicon oxide matrix was assessed for lysozyme purification from undiluted egg white. The matrix can be shaped with big size and high density, thus allowing its efficient separation from the egg white after the adsorption step. The lysozyme-depleted egg white can follow its usual commercialisation route. A surface area of 142 m²/g and a total pore volume of 0.295 cm³/g were calculated from the nitrogen sorption isotherms. Its water content was 78.3%. The matrix structure is the result of the polysaccharide addition to the polymerisation mixture, which is known to influence the condensation process, leading to a material with characteristic properties. A maximum capacity of 117.1 ± 9 mg lysozyme/g and a dissociation constant of 0.73 ± 0.15 mg/mL were calculated from the Langmuir isotherm. A lysozyme purification batch process from undiluted egg white was developed, where 87% of the lysozyme was removed from the egg white and the matrix was easily recovered by a simple filtration through a strainer. The overall yield of the process was 64% with a purification factor of 20.     

Changes in solution color during phenol oxidation by Fenton reagent

Fenton reaction is a highly effective treatment for degrading phenolic compounds in an aqueous solution. However, during phenol oxidation, the oxidized water takes on a dark brown color associated with increased toxicity. Then, although phenol can be completely removed, if the oxidation process is not carried out properly, the final wastewater will be brown in color and have higher toxicity, two parameters in which legislation imposes restrictions. This paper analyzes the development of the dark color observed in the solution under oxidation treatment and formulates a reaction mechanism to explain the color generation. The experiments were carried out following the batch-wise procedure, but with the solution pH being kept constant throughout the reaction at its optimum value for phenol removal, i.e., pH 3.0. It is checked experimentally that color is formed at the beginning of the reaction in less than five minutes, and follows the kinetic-path of a reaction intermediate. During the first steps of the reaction phenol is degraded to dihydroxylated rings (catechol, resorcinol, and hydroquinone). These aromatic intermediates generate higher colored compounds such as ortho- and parabenzoquinone. On the other hand the dihydroxylated rings can react with their own quinones to generate charge-transfer complexes (quinhydrone), compounds which take on a dark color at low concentrations. Moreover, when iron reacts with hydrogen peroxide, ferric ions are generated that can be coordinated to benzene rings to produce colored metal complexes. The observed color of the solution is not a fortuitous result depending on trace components of low significance, but depends directly on the main reaction intermediates, so it is concluded that observed color depends on the level of oxidation reached. The maximum color observable during oxidation treatment (A(o)) depends only on initial phenol concentration and not on oxidant or catalyst doses.     

Manganese-induced growth of GaAs nanowires

GaAs nanowires have been grown on SiO2 and GaAs by molecular beam epitaxy using manganese as growth catalyst. Transmission electron microscopy shows that the wires have a wurtzite-type lattice and that alpha-Mn particles are found at the free end of the wires. X-ray absorption fine structure measurements reveal the presence of a significant fraction of Mn-As bonds, suggesting Mn diffusion and incorporation during wire growth. Transport measurements indicate that the wires are p-type, as expected from doping of GaAs with Mn.     

Broadband ZnO single-nanowire light-emitting diode

We present a novel technique for reliable electrical injection into single semiconductor nanowires for light-emitting diodes and lasers. The method makes use of a high-resolution negative electron-beam resist and direct electron-beam patterning for the precise fabrication of a metallic top contact along the length of the nanowire, while a planar substrate is used as a bottom contact. It can be applied to any nanowire structure with an arbitrary cross section. We demonstrate this technique by constructing the first zinc oxide single-nanowire light-emitting diode. The device exhibits broad sub-bandgap emission at room temperature.     

Ordered assembly of alpha-quinquethiophene on a copper oxide nanotemplate

The organic semiconductor alpha-quinquethiophene (T5) is used as the active layer in organic field-effect transistors. We have investigated the adsorption of T5 on the (110) surface of copper and on the CuO nanotemplate formed by the high-temperature exposure of Cu(110) to molecular oxygen. The results were obtained with high-resolution scanning tunneling microscopy (STM) under ultra-high-vacuum (UHV) conditions. The adsorption of T5 on copper is an important model system because it mimics the active-layer-electrode interface in organic devices. The molecules were observed to adsorb onto both the pristine Cu(110) surface and the CuO nanotemplate, showing a greater affinity for the pristine copper surface. Surprisingly, however, the T5 molecules assembled with a much higher degree of long-range order on the oxygen-passivated portion of the surface.     

In Vitro and In Silico Characterization of an Antimalarial Compound with Antitumor Activity Targeting Human DNA Topoisomerase IB

Human DNA topoisomerase IB controls the topological state of supercoiled DNA through a complex catalytic cycle that consists of cleavage and religation reactions, allowing the progression of fundamental DNA metabolism. The catalytic steps of human DNA topoisomerase IB were analyzed in the presence of a drug, obtained by the open-access drug bank Medicines for Malaria Venture. The experiments indicate that the compound strongly and irreversibly inhibits the cleavage step of the enzyme reaction and reduces the cell viability of three different cancer cell lines. Molecular docking and molecular dynamics simulations suggest that the drug binds to the human DNA topoisomerase IB-DNA complex sitting inside the catalytic site of the enzyme, providing a molecular explanation for the cleavage-inhibition effect. For all these reasons, the aforementioned drug could be a possible lead compound for the development of an efficient anti-tumor molecule targeting human DNA topoisomerase IB.     

Characterization and improvement of rheological properties of sodium caseinate glycated with galactose, lactose and dextran

The aim of this work was to investigate the effect of non-enzymatic glycosylation with galactose, lactose, and 10 kDa dextran on the rheological properties of sodium caseinate. To promote the formation of covalent complexes, the reaction was done in solid state (a_w = 0.67), pH 7.0 (0.1 M sodium phosphate buffer), and temperature set at 50 and 60 °C. The progress of Maillard reaction was indirectly traced by measuring the formation of the Amadori compound, through furosine (2-furoylmethyl-lysine) analysis, and brown polymers, and the resulting glycoconjugates were characterized by LC/ESI-MS and SEC. Results showed a higher reactivity of galactose than lactose and dextran to form the glycoconjugates, due to its smaller molecular weight. Glycation with galactose and lactose increased the viscosity of caseinate and also altered its flow characteristics from Newtonian to shear-thinning. Oscillatory testing showed a higher elastic modulus (G′) in glycoconjugates when compared to non-glycated caseinate, especially with galactose, where a gel-like behaviour was observed after long incubation times. Glycation with dextran did not produce substantial improvements in the rheological properties of caseinate, probably due to the limited extent of the reaction. Our results show that by controlling the rate and extent of the Maillard reaction is a technologically feasible operation to improve the viscosity and gelling properties of sodium caseinate-based ingredients.     

Influence of feasibility constrains on the bidding strategy selection in a day-ahead electricity market session

Large part of liberalized electricity markets, including the Italian one, features an auction mechanism, called day-ahead energy market, which matches producers’ and buyers’ simple bids, consisting of energy quantity and price pairs. The match is achieved by a merit-order economic dispatch procedure independently applied for each of the hours of the following day. Power plants operation should, however, take into account several technical constraints, such as maximum and minimum production bounds, ramp constraints and minimum up and downs times, as well as no-load and startup costs. The presence of these constraints forces to adjust the scheduling provided by the market in order to obtain a feasible scheduling. The paper presents an analysis of the possibility and the limits of taking into account the power plants technical constraints in the bidding strategy selection procedure of generating companies (Gencos). The analysis is carried out by using a computer procedure based both on a simple static game-theory approach and on a cost-minimization unit-commitment algorithm. For illustrative purposes, we present the results obtained for a system with three Gencos, each owning several power plants, trying to model the bidding behaviour of every generator in the system. This approach, although complex from the computational point of view, allows an analysis of both price and quantity bidding strategies and appears to be applicable to markets having different rules and features.     

Anatase-supported vanadium oxide catalysts for o-xylene oxidation: From consolidated certainties to unexpected effects

In this paper some aspects of the reaction of o-xylene oxidation, catalysed by anatase-supported vanadium oxide, are re-examined and compared with the scientific and patent literature. Specifically, the effect of vanadia loading on turnover frequency and on the distribution of products has been investigated, using catalysts having sub-monolayer and above-monolayer vanadium oxide deposited on a high-purity anatase support. It was found that even catalysts having less-than-monolayer vanadia loading, containing isolated or oligomeric VO₄ species, may give good selectivity to phthalic anhydride, provided the support does not catalyze the formation of heavy compounds. Moreover, the effect of water on the reactivity and chemical–physical characteristics of catalysts was studied by means of in situ Raman spectroscopy. Steam promoted dynamic reversible phenomena occurring at the catalyst surface, by facilitating the dispersion of bulk vanadium oxide and therefore increasing the catalyst activity.