Engineered clay products for the paper industry

The need for kaolin pigments by the paper industry with controlled optical and physical properties have significantly changed the type of filler and coating clays available to the paper industry. Processing equipment now used in the production of kaolin products is much more sophisticated and controllable than in the past. Better understanding of the mineralogy and the physical and chemical properties of kaolins, in addition to improved processing techniques, has allowed the kaolin processors to produce engineered or tailored grades that meet particular needs of the user. Particle size and shape, brightness, gloss, opacity, and viscosity can be altered and controlled to meet specific requirements of the paper coater. Examples of several types of engineered products available for use by the paper industry are discussed.     

Highly selective synthesis of 2‐butoxy ethanol over Mg/Al/V mixed oxides catalysts derived from hydrotalcites

The catalytic activity of a series of mixed oxides obtained by the thermal decomposition of hydrotalcite‐like precursors was assessed for the alkoxylation of n-butanol with ethylene oxide. The calcination products of a decavanadate intercalated magnesium–aluminium layered double hydroxide were shown to possess extremely high activity for the alkoxylation reaction achieving up to 100% conversion in batch reaction. In all cases, the catalysts exhibit a much higher selectivity towards the monoglycol adduct than that obtained with the industrial catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

The use of an impure inorganic precursor for the synthesis of highly siliceous mesoporous materials under acidic conditions

Highly ordered mesoporous silica materials have been synthesized under acidic conditions using an industrial waste-product containing only 42 wt% silica as the precursor, using formic acid as pH-regulator. Non-ionic tri-block-co-polymers of the ABA type were used as the structure-directing agents, and high-quality SBA-15 and KIT-5 materials were obtained. The materials were characterized by small-angle X-ray diffraction, nitrogen physisorption, transmission electron microscopy, and elemental analysis. The methodology presented here is suggested to be widely applicable for the synthesis of siliceous materials using other impure inorganic silica precursors with different purity, as long as the precursors are soluble under acidic conditions.     

Variations in IC50 Values with Purity of Mushroom Tyrosinase

The effects of various inhibitors on crude, commercial and partially purified commercial mushroom tyrosinase were examined by comparing IC₅₀ values. Kojic acid, salicylhydroxamic acid, tropolone, methimazole, and ammonium tetrathiomolybdate had relatively similar IC₅₀ values for the crude, commercial and partially purified enzyme. 4-Hexylresorcinol seemed to have a somewhat higher IC₅₀ value using crude extracts, compared to commercial or purified tyrosinase. Some inhibitors (NaCl, esculetin, biphenol, phloridzin) showed variations in IC₅₀ values between the enzyme samples. In contrast, hydroquinone, lysozyme, Zn²⁺, and anisaldehyde showed little or no inhibition in concentration ranges reported to be effective inhibitors. Organic solvents (DMSO and ethanol) had IC₅₀ values that were similar for some of the tyrosinase samples. Depending of the source of tyrosinase and choice of inhibitor, variations in IC₅₀ values were observed.     

Using chemistry and microfluidics to understand the spatial dynamics of complex biological networks

Understanding the spatial dynamics of biochemical networks is both fundamentally important for understanding life at the systems level and also has practical implications for medicine, engineering, biology, and chemistry. Studies at the level of individual reactions provide essential information about the function, interactions, and localization of individual molecular species and reactions in a network. However, analyzing the spatial dynamics of complex biochemical networks at this level is difficult. Biochemical networks are nonequilibrium systems containing dozens to hundreds of reactions with nonlinear and time-dependent interactions, and these interactions are influenced by diffusion, flow, and the relative values of state-dependent kinetic parameters. To achieve an overall understanding of the spatial dynamics of a network and the global mechanisms that drive its function, networks must be analyzed as a whole, where all of the components and influential parameters of a network are simultaneously considered. Here, we describe chemical concepts and microfluidic tools developed for network-level investigations of the spatial dynamics of these networks. Modular approaches can be used to simplify these networks by separating them into modules, and simple experimental or computational models can be created by replacing each module with a single reaction. Microfluidics can be used to implement these models as well as to analyze and perturb the complex network itself with spatial control on the micrometer scale. We also describe the application of these network-level approaches to elucidate the mechanisms governing the spatial dynamics of two networkshemostasis (blood clotting) and early patterning of the Drosophila embryo. To investigate the dynamics of the complex network of hemostasis, we simplified the network by using a modular mechanism and created a chemical model based on this mechanism by using microfluidics. Then, we used the mechanism and the model to predict the dynamics of initiation and propagation of blood clotting and tested these predictions with human blood plasma by using microfluidics. We discovered that both initiation and propagation of clotting are regulated by a threshold response to the concentration of activators of clotting, and that clotting is sensitive to the spatial localization of stimuli. To understand the dynamics of patterning of the Drosophila embryo, we used microfluidics to perturb the environment around a developing embryo and observe the effects of this perturbation on the expression of Hunchback, a protein whose localization is essential to proper development. We found that the mechanism that is responsible for Hunchback positioning is asymmetric, time-dependent, and more complex than previously proposed by studies of individual reactions. Overall, these approaches provide strategies for simplifying, modeling, and probing complex networks without sacrificing the functionality of the network. Such network-level strategies may be most useful for understanding systems with nonlinear interactions where spatial dynamics is essential for function. In addition, microfluidics provides an opportunity to investigate the mechanisms responsible for robust functioning of complex networks. By creating nonideal, stressful, and perturbed environments, microfluidic experiments could reveal the function of pathways thought to be nonessential under ideal conditions.     

Processing of Polymer-Derived Ceramic Composite Coatings on Steel

Polymer-derived ceramic composites are being investigated as environmental barrier coatings to protect stainless steel from oxidation and carburization. Coatings have been produced using poly(hydridomethylsiloxane) as a preceramic polymer and titanium disilicide as an expansion agent. Processing parameters have been optimized and a relationship has been derived to predict the final coating thickness based on slurry viscosity and dip coating withdrawal speed. Microstructural analysis reveals a composite coating of oxidized filler particles in a silica matrix. A diffusion layer is visible at the coating–steel interface, indicating good bonding. The optimized coatings are ∼18 μm thick, and have some residual porosity and a density of 2.56 g/cm³.     

Antimicrobial and Anticancer Properties of Synthetic Peptides Derived from the Wasp Parachartergus fraternus

Agelaia-MPI and protonectin are antimicrobial peptides isolated from the wasp Parachartergus fraternus that show antimicrobial and neuroactive activities. Previously, two analogues of these peptides, neuroVAL and protonectin-F, were designed to reduce nonspecific toxicity and improve potency. Here, the three-dimensional structures of neuroVAL, protonectin and protonectin-F were determined by using circular dichroism and NMR spectroscopy. Antibacterial, antifungal, cytotoxic and hemolytic activities were tested for the parent peptides and analogues. All peptides showed moderate antimicrobial activity against Gram-positive bacteria, with agelaia-MPI being the most active. Protonectin and protonectin-F were found to be toxic to cancerous and noncancerous cell lines. Internalization experiments revealed that these peptides accumulate inside both cell types. By contrast, neuroVAL was nontoxic to all tested cells and was able to enter cells without accumulating. In summary, neuroVAL has potential as a nontoxic cell-penetrating peptide, while protonectin-F needs further modification to realize its potential as an antitumor peptide.     

Chemical Synthesis and Biological Applications of O-GlcNAcylated Peptides and Proteins

All human cells use O-GlcNAc protein modifications (O-linked N-acetylglucosamine) to rapidly adapt to changing nutrient and stress conditions through signaling, epigenetic, and proteostasis mechanisms. A key challenge for biologists in defining precise roles for specific O-GlcNAc sites is synthetic access to homogenous isoforms of O-GlcNAc proteins, a result of the non-genetically templated, transient, and heterogeneous nature of O-GlcNAc modifications. Toward a solution, this review details the state of the art of two strategies for O-GlcNAc protein modification: advances in “bottom-up” O-GlcNAc peptide synthesis and direct “top-down” installation of O-GlcNAc on full proteins. We also describe key applications of synthetic O-GlcNAc peptide and protein tools as therapeutics, biophysical structure–function studies, biomarkers, and as disease mechanistic probes to advance translational O-GlcNAc biology.     

Development of a difunctional oxirane and multifunctional acrylate interpenetrating polymer network composite system with antimicrobial properties

This research continued the development of a difunctional Oxirane and multifunctional Acrylate interpenetrating polymer network composite System (OASys) with antimicrobial properties. The effects of 4-Isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate (Borate), hexamethylene diamine (HMDA) and N,N-dimethyl p-toluidine (DMPT) on OASys (Epalloy 5001:dipentaerythritol hexaacrylate) composite hardness, contact angle, monomer-to-polymer degree of conversion (DoC), mechanical properties, polymerization shrinkage, shrinkage stress, and antimicrobial properties were determined. Bis-GMA:TEGDMA composites were used as the control. OASys composites with 9 wt% Borate and 0.5 wt% DMPT or 1.5 wt% HMDA had comparable hardness, DoC's and polymerization shrinkages to controls, but had lower contact angles and mechanical properties. Additionally, OASys composites with 1.5 wt% HMDA had significantly less polymerization stress than controls and demonstrated significant antibacterial activity against Streptococcus mutans and Lactobacillus casei out to 3 months. With lower shrinkage stress and long-term antimicrobial activity, OASys composites look promising for increasing the clinical lifetime of dental composites, but improvements in mechanical properties are needed.