Electrodeposition of porous Co layers and their conversion to electrocatalysts for methanol oxidation by spontaneous deposition of Pd

Electrocatalysts for methanol oxidation were prepared through a two stage deposition process: porous cobalt layers were deposited, by cathodic reduction of Co²⁺ ions, and then modified by spontaneous deposition of Pd. A basic sulphate solution and a mildly acid chloride solution were compared as media for the electrodeposition of Co. Deposits with the highest surface roughness were obtained in the chloride solution, at large current densities. Pd was deposited onto the Co porous layers by immersing them in acid deaerated PdCl₂ solutions, at open circuit. The Pd loading and the Pd surface area were estimated by UV–visible spectroscopy and by cyclic voltammetry, respectively. The Pd-modified Co electrodes were tested as anodes for methanol oxidation and compared to the similarly prepared Pd-modified Ni electrodes. The former exhibited better stability of performance and higher methanol oxidation peak currents per unit Pd mass, ca. 200 A g⁻¹.     

Production of active recombinant eIF5A: reconstitution in E.coli of eukaryotic hypusine modification of eIF5A by its coexpression with modifying enzymes

Eukaryotic translation initiation factor 5A (eIF5A) is the only cellular protein that contains the polyamine-modified lysine, hypusine [N(ε)-(4-amino-2-hydroxybutyl)lysine]. Hypusine occurs only in eukaryotes and certain archaea, but not in eubacteria. It is formed post-translationally by two consecutive enzymatic reactions catalyzed by deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase (DOHH). Hypusine modification is essential for the activity of eIF5A and for eukaryotic cell proliferation. eIF5A binds to the ribosome and stimulates translation in a hypusine-dependent manner, but its mode of action in translation is not well understood. Since quantities of highly pure hypusine-modified eIF5A is desired for structural studies as well as for determination of its binding sites on the ribosome, we have used a polycistronic vector, pST39, to express eIF5A alone, or to co-express human eIF5A-1 with DHS or with both DHS and DOHH in Escherichia coli cells, to engineer recombinant proteins, unmodified eIF5A, deoxyhypusine- or hypusine-modified eIF5A. We have accomplished production of three different forms of recombinant eIF5A in high quantity and purity. The recombinant hypusine-modified eIF5A was as active in methionyl-puromycin synthesis as the native, eIF5A (hypusine form) purified from mammalian tissue. The recombinant eIF5A proteins will be useful tools in future structure/function and the mechanism studies in translation.     

Post Consumer Pet Depolymerization by Acid Hydrolysis

The reaction of post-consumer poly(ethylene terephthalate) with aqueous solutions of sulfuric acid 7.5 M was investigated in terms of temperature, time and particle size. The reaction extent reached 80% in four days at 100°C and 90% in 5 hours at 135°C. TPA obtained was purified and considered in the same level of quality of the commercial one after tests of elemental analysis, particle size and color. It was concluded that the hydrolysis occurred preferentially at the chain ends and superficially, having as controller mechanism the acid diffusion into the polymer structure. The shrinking-core model can explain the reaction kinetics.     

Laminar,transitional and turbulent friction factors for gas flows in smooth and rough microtubes

Theoretical and experimental works on microscale transport phenomena have been carried out in the past decade in the attempt to analyze possible new effects and to assess the influence of downscaling on the classical correlations which are used in macro-scale heat and fluid flow, following the need to supply engineers with reliable tools to be used in the design of micro-scale devices. These results were sometimes in mutual contrast, as is the case for the determination of the friction factor, which has been found to be lower, higher or comparable to that for macroscopic channels, depending on the researchers. In this work the compressible flow of nitrogen inside circular microchannels from 26 μm to 508 μm in diameter and with different surface roughness is investigated for the whole range of flow conditions: laminar, transitional and turbulent. Over 5000 experimental data have been collected and analysed. The data confirmed that in the laminar regime the agreement with the conventional theory is very good in terms of friction factors both for rough and smooth microtubes. For the smaller microchannels (<100 μm) when Re is greater than 1300 the friction factor tends to deviate from the Poiseuille law because the flow acceleration due to compressibility effects gains in importance. The transitional regime was found to start no earlier than at values of the Reynolds number around 1800. Both smooth and sudden changes in the flow regime have been found, as reported for conventional tubes. Fully developed turbulent flow was attained with both smooth and rough tubes, and the results for smooth tubes seem to confirm Blasius' relation, while for rough tubes the Colebrook–White correlation is found to be only partially in agreement with the experimental friction factors. In the turbulent regime the dependence of the friction factor on the Reynolds number is less pronounced for microtubes than the prediction of the Colebrook–White correlation and the friction factor depends only on the microtube “relative roughness”.     

Metabolites from the biodegradation of di-ester plasticizers by Rhodococcus rhodochrous

The plasticizers di-2-ethylhexyl phthalate (DEHP) and di-2-ethylhexyl adipate (DEHA) are ubiquitous in the environment and undergo partial biodegradation in the presence of soil micro-organisms. The validity of a proposed pathway for the degradation of these plasticizers by Rhodococcus rhodochrous has been confirmed by the identification of 2-ethylhexanal in gas phase emissions. Complete analyses of the aqueous and gas phases were able to account for more than 98% of the 2-ethylhexanol component of the DEHA added at the beginning of a growth study. Of this, 25% was either 2-ethylhexanol or 2-ethylhexanal that had been stripped into the gas phase and, at most, only 2% of the 2-ethylhexanol component could have been removed by mineralization. It is concluded that plasticizers are of significant environmental concern due to the resistance of the metabolites to biodegradation and their known health impacts. Two of the metabolites are of added concern due to their volatility and their potential impact on indoor air quality.     

Preparation,characterization, and antimicrobial activity of ferrocene-containing polymeric materials

Ferrocenyl(benzyl) imidazole (FcIm) and two related methyl-imidazolium salts (FcMIm⁺I^– and FcMIm⁺PF₆^–) were synthesized for their incorporation into plasticized PVC by solvent casting technique. The obtained materials were investigated for their thermal stability and, compared to pure polymer, films containing ionic ferrocene derivatives in 0.5% w/w loading were found slightly more stable. The pure ferrocene compounds showed antibacterial activity against Staphylococcus epidermis, but not against Escherichia coli, with a maximum for FcMIm⁺PF₆^– salt. After incorporation into PVC polymer, antibacterial activity against S. epidermis was observed (by disk diffusion test) only for PVC/FcMIm⁺PF₆^– (5% w/w) film, from which a release of 14.6% of the ferrocenilimidazolium cation in aqueous medium was measured after 24 hr.