Preceramic polymer‐derived SiOC fibers by electrospinning

Silicon oxycarbide (SiOC) fibers with different chemical compositions were successfully fabricated by electrospinning a mixture of polyvinylpyrrolidone (PVP) and commercially available polymethylsilsesquioxane (MK) or polymethylphenylsilsesquioxane (H44) preceramic polymers, followed by cross‐linking and pyrolysis at 1000°C in Argon. The influence of the processing procedure (solvent selection, cross‐linking catalyst and additives) on the morphology of the produced fibers was investigated. For the MK/isopropanol system, the introduction of 20 vol% N,N‐dimethylformamide (DMF) enabled to decrease the diameter of the as‐spun fibers from 2.72 ± 0.12 μm to 1.65 ± 0.09 μm. For the H44/DMF systems, beads‐free fibers were obtained by adding 50 vol% choloroform. After pyrolysis, the resultant SiOC fibers derived from MK and H44 resins possessed uniform morphology, with an average diameter of 0.97 ± 0.07 μm and 1.07 ± 0.08 μm, respectively. Due to their different chemical compositions, the MK‐derived and H44‐derived SiOC ceramic fibers could find different potential applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39836.     

How Different Characterization Techniques Elucidate the Nature of the Gold Species in a Polycrystalline Au/TiO2 Catalyst

TiO₂‐supported gold species were prepared via the deposition‐precipitation route, with conservation of the initial speciation by freeze‐drying. The structural and electronic properties of the Au species were investigated by X‐ray absorption spectroscopy, electron microscopy, and IR spectroscopy of adsorbed CO in four states. Exclusively Au^III was deposited on the TiO₂ surface in patches ranging from isolated Au ions to three‐dimensional clusters. This paper illustrates in detail the unique contributions of all characterization techniques to this structural model.     

Functional mesoporous poly(ionic liquid)-based copolymer monoliths: From synthesis to catalysis and microporous carbon production

Ionic liquid-functionalized mesoporous polymeric networks with specific surface area up to 935 m²/g have been successfully synthesized one pot by solvothermal copolymerization of divinylbenzene and monomeric ionic liquids. The as-obtained polymers exhibit a monolithic structure featuring large pore volumes, an abundant mesoporosity and an adjustable content of ionic liquids. The effect of the reaction conditions on the pore structure has been studied in detail. These poly(ionic liquid)-based porous networks (PILPNs) have then been employed as precursors in two distinct applications, namely organocatalysis and production of microporous carbon monoliths. Selected organocatalyzed reactions, including carbonatation of propylene oxide by cycloaddition with carbon dioxide, benzoin condensation, and cyanosilylation of benzaldehyde have been readily triggered by PILPNs acting as crosslinked polymer-supported (pre)catalysts. The two latter reactions required the prior deprotonation of the imidazolium salt units with a strong base to successfully generate polymer-supported N-heterocyclic carbenes, referred to as poly(NHC)s. Facile recycling and reuse of polymer-supported (pre)catalysts was achieved by simple filtration owing to the heterogeneous reaction conditions. Furthermore, PILPNs could be easily converted into microporous carbon monoliths via CO₂ activation.     

Integrodifferential approach to solution of eddy currents in linear structures with motion

A nonstandard integrodifferential approach to computation of eddy currents in linear structures with motion is presented. Described is a general continuous 3D model of the problem, together with the possibilities of forming corresponding numerical schemes. The methodology is illustrated by two examples.     

Hierarchical virtual screening for the discovery of new molecular scaffolds in antibacterial hit identification

One of the initial steps of modern drug discovery is the identification of small organic molecules able to inhibit a target macromolecule of therapeutic interest. A small proportion of these hits are further developed into lead compounds, which in turn may ultimately lead to a marketed drug. A commonly used screening protocol used for this task is high-throughput screening (HTS). However, the performance of HTS against antibacterial targets has generally been unsatisfactory, with high costs and low rates of hit identification. Here, we present a novel computational methodology that is able to identify a high proportion of structurally diverse inhibitors by searching unusually large molecular databases in a time-, cost- and resource-efficient manner. This virtual screening methodology was tested prospectively on two versions of an antibacterial target (type II dehydroquinase from Mycobacterium tuberculosis and Streptomyces coelicolor), for which HTS has not provided satisfactory results and consequently practically all known inhibitors are derivatives of the same core scaffold. Overall, our protocols identified 100 new inhibitors, with calculated K_i ranging from 4 to 250 μM (confirmed hit rates are 60% and 62% against each version of the target). Most importantly, over 50 new active molecular scaffolds were discovered that underscore the benefits that a wide application of prospectively validated in silico screening tools is likely to bring to antibacterial hit identification.     

Multimorphing: A tool for shape synthesis and analysis

Morphing is a shape transformation where the shape of one object is deformed to the shape of the other object. It is used as an animation or a modeling technique. Classical morphing operates between two input objects but this concept can be extended to multiple input objects – the so called multimorphing. Shapes generated by the multimorphing form a space of shapes motivated by an affine space. Besides the analogy with an affine space we also introduce an inner product and a concept of an orthogonal projection. We also show how to explore space of shapes and how to systematically generate new shapes. The paper focuses on the boundary representation, although some ideas are more general and can be used for other representations, too.     

Bioinspired pressure actuated adhesive system

We developed a dry synthetic adhesive system inspired by gecko feet adhesion that can switch reversibly from adhesion to non-adhesion with applied pressure as external stimulus. Micropatterned polydimethylsiloxane (PDMS) surfaces with pillars of 30 μm length and 10 μm diameter were fabricated using photolithography and moulding. Adhesion properties were determined with a flat probe as a function of preload. For low and moderate applied compressive preloads, measured adhesion was 7.5 times greater than on flat controls whereas for high applied preloads adhesion dropped to very low values. In situ imaging shows that the increased preload caused the pillars to deform by bending and/or buckling and to lose their adhesive contact. The elasticity of PDMS aids the pillar recovery to the upright position upon removal of preload enabling repeatability of the switch.     

Radiosensitization of Human Leukemic HL-60 Cells by ATR Kinase Inhibitor (VE-821): Phosphoproteomic Analysis

DNA damaging agents such as ionizing radiation or chemotherapy are frequently used in oncology. DNA damage response (DDR)—triggered by radiation-induced double strand breaks—is orchestrated mainly by three Phosphatidylinositol 3-kinase-related kinases (PIKKs): Ataxia teleangiectasia mutated (ATM), DNA-dependent protein kinase (DNA-PK) and ATM and Rad3-related kinase (ATR). Their activation promotes cell-cycle arrest and facilitates DNA damage repair, resulting in radioresistance. Recently developed specific ATR inhibitor, VE-821 (3-amino-6-(4-(methylsulfonyl)phenyl)-N-phenylpyrazine-2-carboxamide), has been reported to have a significant radio- and chemo-sensitizing effect delimited to cancer cells (largely p53-deficient) without affecting normal cells. In this study, we employed SILAC-based quantitative phosphoproteomics to describe the mechanism of the radiosensitizing effect of VE-821 in human promyelocytic leukemic cells HL-60 (p53-negative). Hydrophilic interaction liquid chromatography (HILIC)-prefractionation with TiO₂-enrichment and nano-liquid chromatography—tandem mass spectrometry (LC-MS/MS) analysis revealed 9834 phosphorylation sites. Proteins with differentially up-/down-regulated phosphorylation were mostly localized in the nucleus and were involved in cellular processes such as DDR, all phases of the cell cycle, and cell division. Moreover, sequence motif analysis revealed significant changes in the activities of kinases involved in these processes. Taken together, our data indicates that ATR kinase has multiple roles in response to DNA damage throughout the cell cycle and that its inhibitor VE-821 is a potent radiosensitizing agent for p53-negative HL-60 cells.     

How the interactions with humic acids affect the mobility of ionic dyes in hydrogels – Results from diffusion cells

The complexation of charged compounds by humic acids represents the process of exceptional environmental importance. Nevertheless, traditional methods utilized in the complexation studies do not address the way, how these interactions affect the transport of ions in humic-rich environments. To overcome this dilemma, the diffusion cells technique is proposed as an innovative reactivity mapping technique. Using this method, the diffusion of methylene blue was studied in aqueous solutions and in agarose gels with and without the addition of humic acids. Experimental results clearly illustrate the immobilizing effects of humic acids on the transport of methylene blue in gels. The partitioning of methylene blue at the solution-gel interface and the specific interactions between methylene blue and humic acids is discussed on the basis of experimental data. Effective structural parameters of hydrogels (effective porosity, tortuosity factor) were calculated, as well as some standard diffusion and interaction parameters (diffusion and partition coefficients and apparent equilibrium constants).