Towards a Universal Method for the Stable and Clean Functionalization of Inert Perfluoropolymer Nanoparticles: Exploiting Photopolymerizable Amphiphilic Diacetylenes

Highly fluorinated materials are being widely investigated due to a number of peculiar properties, which are potentially useful for various applications, including use as lubricants, anti‐adhesive films, and substitutes for biological fluids for biomedical utilization. However, at present such potential is still poorly exploited. One of the major drawbacks that hampers the rapid development of nanoscale fluoro‐hybrid devices is the remarkable inertness of perfluoropolymeric materials that lack reactive functionalities, as they do not offer any functional groups that can be employed to covalently anchor organic molecules on their surface. In this paper, a convenient method for the stable biofunctionalization of strongly unreactive perfluoropolymer nanoparticles (PnPs) is reported. PnPs are easily coated with newly synthesized asymmetric diacetylenic monomer compounds (ADMs), thanks to PnP’s high propensity to interact with hydrophobic moieties. Once monomerically adsorbed onto PnPs, such suitably designed ADMs enable the formation of a robust polymeric shell around the perfluoroelastomer core via a clean UV‐promoted localized photopolymerization. Given the peculiar optical characteristics of PnPs, the coating of the particles can be monitored step by step using light scattering, which also allows estimation of the fraction of reacted monomers by competitive adsorption with smaller particles. The potential of this method for the biofunctionalization of PnPs is demonstrated with representative proteins and carbohydrates. Among them, the extension to avidin–biotin technology may broaden the scope and applicability of this strategy to potentially a large number of molecules of biomedical interest.     

RELATION BETWEEN THE DISSOLUTION REACTIVITY OF POWDER SUBSTANCES AND EFFICIENCY OF THEIR ELECTROPLATING

ABSTRACT

The importance of the passivation layer on Fe powder surfaces formed by oxides, hydroxides, and/or salts and water molecules is pointed out for both electrochemical oxidative dissolution of iron powder and electrodeposition of Ni layer on it. This layer behaves as ohmic contact resistance. The layer thickness affects the surface reactivity of the powder and is influenced by the way of preactivation the powder prior to the electrochemical process. A reliable voltammetric method reflecting the surface reactivity was found, theoretically treated, and experimentally verified by measuring the rate of electrochemical dissolution of Fe powder. The efficiency of Ni electrodeposition on this powder was determined in a series of independent electrolyses. The correlation between both later mentioned parameters was satisfying for small powder particle fractions as well as for activation procedures which include chemical step.     

Concentration of flavonoids and phenolic compounds in aqueous and ethanolic propolis extracts through nanofiltration

Propolis has a variable and complex chemical composition with high concentration of flavonoids and phenolic compounds present in the extract. The extract varies with the solvent used in extraction. Ethanol extracts more phenolic acid and polar compounds than water. Before their use in industry, extracts must be concentrated but the use of high temperatures can degrade some compounds. Membrane processes is an option that allows concentration at low temperatures. Nanofiltration was carried out with aqueous and ethanolic extracts and each extract results in two distinct fractions: permeate and retentate. The capacity of the membrane to retain the compounds was verified by spectrophotometric analysis: for aqueous solution, the membrane retained around 94% of the phenolic compounds and 99% of the flavonoids, while for the ethanolic solution these values were 53% and 90%, respectively. Ferulic acid retention index was 1.00 and 0.88 to aqueous and ethanolic solutions, respectively. Thus, the nanofiltration process showed high efficiency in the concentration of propolis extracts.     

Volatile compound production in Agave duranguensis juice fermentations using four native yeasts and NH4Cl supplementation

Nitrogen has a significant effect on the fermentation rate and the chemical composition of alcoholic beverages. Nitrogen deficiency during fermentation of Agave juice for mescal production can lead to slow fermentations and end-products with low aromatic compound variety. In this study, the effects of NH₄Cl supplementation on volatile compound formation in Agave duranguensis juice fermented at 28?°C with the native yeast strains Saccharomyces cerevisiae ITD00185, Hanseniaspora uvarum ITD00108, Torulaspora delbrueckii ITD00110 and Kluyveromyces marxianus ITD00211 were analysed. Nitrogen content in the Agave juice unsupplemented with NH₄Cl was low. In the control treatments, the four yeasts consumed nitrogen at approximately the same rate, almost completely finishing by 24?h. Nitrogen supplementation increased biomass production with S. cerevisie, H. uvarum and T. delbrueckii but not with K. marxianus. K. marxianus consumed the total assimilable nitrogen more slowly than the other strains in the supplemented fermentations. In addition, the volatile compound profile differed between the studied yeasts. Volatile compound production by S. cerevisiae, H. uvarum and K. marxianus was higher in the supplemented fermentations, compared to the unsupplemented ones. In T. delbrueckii, the initial volatile compound concentrations remained unchanged, or decreased for some compounds, with nitrogen supplementation. The initial acetic acid and vanillin concentrations decreased with all strains tested and nitrogen supplementation. Furthermore, the concentration of higher alcohols increased with S. cerevisiae and H. uvarum in the NH₄Cl-supplemented fermentations, but they decreased with T. delbrueckii and K. marxianus. In conclusion, the addition of an inorganic nitrogen source promotes microorganism metabolism, increases biomass formation and benefits the fermentation process.     

Antioxidant activity and polyphenol contents in Brazilian green propolis extracts prepared with the use of ethanol and water as solvents in different pH values

Propolis is a natural product with a variable and complex chemical composition associated with its high concentration on polyphenolic compounds. The effect of pH variation (2.0, 3.0, 4.3, 6.0 and 8.0) during aqueous and ethanolic propolis extraction was studied for up to 10 days. Total phenols and flavonoids contents were measured for the extracts by spectrophotometric assays. Antioxidant activity was measured by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and ferric thiocyanate (FTC) methods. The best time of extraction was up to 5 days for all samples. Basic aqueous extracts (pH 8.0) resulted in a higher concentration of compounds than the extract without pH modification, reaching an increase of 160% in flavonoids and 25% in phenols. Ethanolic extracts with pH variation resulted in an extract with 50% less polyphenols and 6% less flavonoids than extract without pH modification. The antioxidant activity was highest for ethanolic extract at pH 4.3 and aqueous extract at pH 8.0 – almost 90% and 45%, respectively, in DPPH method – and was related to the level of polyphenols by Pearson's correlations.     

Social and Heuristic Approaches to Credibility Evaluation Online

The tremendous amount of information available online has resulted in considerable research on information and source credibility. The vast majority of scholars, however, assume that individuals work in isolation to form credibility opinions and that people must assess information credibility in an effortful and time‐consuming manner. Focus group data from 109 participants were used to examine these assumptions. Results show that most users rely on others to make credibility assessments, often through the use of group‐based tools. Results also indicate that rather than systematically processing information, participants routinely invoked cognitive heuristics to evaluate the credibility of information and sources online. These findings are leveraged to suggest a number of avenues for further credibility theorizing, research, and practice.     

Molybdenum(VI) Amino Triphenolate Complexes as Catalysts for Sulfoxidation,Epoxidation and Haloperoxidation

Two molybdenum(VI) complexes bearing a C₃ symmetrical amino tris‐tert‐butylphenolate ligand have proved to be air‐ and water‐tolerant catalysts that efficiently catalyse, in high yields and selectivity, the oxidation of sulfides, olefins and halides. In particular high turnover frequencies and turnover numbers (TOF and TON) have been obtained for the cyclooctene epoxidation (catalyst loading down to 0.05%, TONs up to 88,000 and TOFs up to 7500 h⁻¹).     

Purification of Minute Virus of Mice using high performance tangential flow filtration

Membrane technology has proven to be a mainstay separation technology over the past two decades. Some major advantages of membrane technology are application without the addition of chemicals and a comparatively low energy use. With its current applications, membrane technology has been widely used in biotechnology processes. Cell harvesting and virus purification/removal are important processes in many downstream purifications of biopharmaceutical products. For this project, ultrafiltration (UF) for virus purification from cell culture broth was used. Recently, it has been demonstrated that UF is a powerful tool for purification of other viruses such as Aedes aegypti and virus-like particles. More precisely, high performance tangential flow filtration (HPTFF) will be used, which was first introduced by Robert van Reis in 1997. To date HPTFF has been used in other projects, as for protein concentration, purification, and buffer exchange as a single unit operation. The virus used in this study was the parvovirus Minute Virus of Mice (MVM); characterized by an average diameter of 22-26 nm and icosahedral symmetry. Experiments were conducted with 300, 100 and 50 kDa Sartorius membranes. Results obtained indicate that using the 50 or 100 kDa membrane, viral particles get excluded, whereas the 300 kDa membrane allows the passage of the virus particles into the permeate. In HPTFF mode the permeate flux decline of the 300 kDa ultrafiltration membrane is much greater than for the other membranes used. One possible explanation for this decay could have to do with the virus particles' access to the membrane pores (gradual pore narrowing). Additionally the permeate flux and level of protein rejection as well, are strongly affected by the cell culture medium.     

Macroporous bead modification with polyethylenimines of different molecular weights as polycationic ligands

Polyethylenimines (PEIs) with different molecular weights [number‐average molecular weights (M_n′s) = 60,000, 1200, and 423] were coupled onto macroporous beads. These rigid and spherical beads were prepared by the crosslinking of 2‐hydroxyethyl methacrylate and ethylene glycol dimethacrylate. The PEI attachment was carried out through epoxy groups yielded in a previous activation step with epichlorohydrin on matrix hydroxyl groups. Different initial concentrations of PEI were assayed. The supports so obtained were characterized by several techniques (Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mercury intrusion porosimetry). All of the PEI‐containing beads were used to analyze the influence that the molecular weight, the shape of the polycationic ligand (PEI), and the degree of coupling onto the matrices may have had on the efficiency of the retention of the bovine serum albumin protein used as a model biomolecule. In these assays, the PEI‐modified beads with M_n = 60,000 showed better results than those modified with PEIs with M_n's of 1200 and 423. The presence of sparse and long chains of PEI 60,000 onto the matrix, by reason of their highest accessibility toward the large protein, may have resulted in a better disposition of functional groups, whereas more short chains in the other PEIs (M_n's = 1200 and 423) used as ligands would not have. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010