Analysis of the topochemical effects of dielectric-barrier discharge on cellulosic fibers

This study investigates the fundamental topochemical effects of dielectric-barrier discharge treatment on bleached chemical pulp and unbleached mechanical pulp fiber surfaces. Fibers were treated with various levels of dielectric-barrier discharge treatment ranging from 0 to 9.27 kW/m²/min. Changes to the fiber surface topochemistry were investigated by atomic force microscopy (AFM). The AFM studies were complemented by inverse gas chromatography (IGC), contact angle evaluation, poly-electrolyte titration, viscosity testing and determination of water retention value (WRV). The static coefficient of friction and zero-span tensile index of sheets were also evaluated. Low dielectric-barrier discharge treatment levels resulted in increased surface energy and roughness. Fibers treated at high applied power levels showed surface energies and roughness levels near that of reference samples as well as evidence of degradation and decreased fiber swelling.     

The synthesis of pyridazino[4,5-d] pyridazines,pyrazino [2,3-d] pyridazines and a pyrimido [4,5-d] pyridazine

The synthetic chemistry of the relatively unknown pyridazino [4,5-d]pyridazine ring system has been extended. 1,4-Diaminopyridazino [4,5-d]pyridazine (VIII) has been prepared by two routes, the most interesting of these being the one-step conversion of 4,5-dicyanopyridazine into VIII with hydrazine. Upon nitration VIII gave only the mononitramine (X). Attempts to prepare 1,4-dichloropyridazino [4,5-d]pyridazine gave only 4-chloro-2H-pyridazino [4,5-d]pyridazin-1-one (XII). Pyrimido [4,5-d]pyridazine-1,3-dione (XIV) was prepared from pyridazine-4,5-dicarboxamide (IV). The hydrolysis of 5,8-dichloropyrazino [2,3-d]pyridazine (XV) gave 5-chloropyrazino [2,3-d]pyridazin-8-one (XVII) and likewise the ammonolysis of XV gave 5-amino-8-chloropyrazino [2,3-d]pyridazine (XX). As expected the hydrolysis of 5,8-dibromo-pyrazino [2,3-d]pyridazine (XXI) gave 5-bromopyrazino [2,3-d]pyridazin-8-one (XXII). Attempted catalytic dechlorination of 5-chloropyrazino [2,3-d]pyridazin-8-one (XVII) gave 1,2,3,4-tetrahydropyrazino [2,3-d]pyridazin-5-one (XIX).     

Protective effects of an antioxidant derived from serine and vitamin B6 on skin photoaging in hairless mice

The generation of reactive oxygen species (ROS) by ultraviolet radiation (UVR) accelerates skin aging, which is known as photoaging. Because cutaneous iron catalyzes ROS generation, sequestering iron by chelating agents is thought to be an effective approach toward preventing photoaging. Previously, N-(4-pyridoxylmethylene)-l-serine (PYSer) was designed as an antioxidant to suppress iron-catalyzed ROS generation by its iron-sequestering activity. In this study, PYSer showed protective effects against skin damage in hairless mice irradiated with ultraviolet B (UV-B). Topical application of PYSer to the skin significantly delayed and/or decreased the visible wrinkle formation induced by chronic UV-B irradiation. A histological study indicated that UV-B-induced epidermal hypertrophy and lymphocytic infiltration were suppressed by PYSer. Moreover, PYSer showed suppressive activity against the UV-B-induced increase in glycosaminoglycans (GAG). These results indicate that PYSer is a promising antioxidant for the prevention of chronic skin photoaging by its iron-sequestering activity.     

Peptide amphiphile nanofibers with conjugated polydiacetylene backbones in their core

The coupling of electronic and biological functionality through self-assembly is an interesting target in supramolecular chemistry. We report here on a set of diacetylene-derivatized peptide amphiphiles (PAs) that react to form conjugated polydiacetylene backbones following self-assembly into cylindrical nanofibers. The polymerization reaction yields highly conjugated backbones when the peptidic segment of the PAs has a linear, as opposed to a branched, architecture. Given the topotactic nature of the polymerization, these results suggest that a high degree of internal order exists in the supramolecular nanofibers formed by the linear PA. On the basis of microscopy, the formation of a polydiacetylene backbone to covalently connect the beta-sheets that help form the fibers does not disrupt the fiber shape. Interestingly, we observe the appearance of a polydiacetylene (PDA) circular dichroism band at 547 nm in linear PA nanofibers suggesting the conjugated backbone in the core of the nanostructures is twisted. We believe this CD signal is due to chiral induction by the beta-sheets, which are normally twisted in helical fashion. Heating and cooling shows simultaneous changes in beta-sheet and conjugated backbone structure, indicating they are both correlated. At the same time, poor polymerization in nanofibers formed by branched PAs indicates that less internal order exists in these nanostructures and, as expected, then a circular dichroism signal is not observed for the conjugated backbone. The general variety of materials investigated here has the obvious potential to couple electronic properties and in vitro bioactivity. Furthermore, the polymerization of monomers in peptide amphiphile assemblies by a rigid conjugated backbone also leads to mechanical robustness and insolubility, two properties that may be important for the patterning of these materials at the cellular scale.     

Proteomic analysis of conditioned media from glucose responsive and glucose non-responsive phenotypes reveals a panel of secreted proteins associated with beta cell dysfunction

Media conditioned by dysfunctioning pancreatic beta cells offer an excellent source of potential protein markers associated with this phenotype. Proteins identified from cell culture model systems are often found to be of importance clinically. Previous work by us and others have shown that low-passage MIN-6 cells (MIN-6(L)) respond to changes in glucose concentrations, producing an approximately 5.5-fold glucose-stimulated insulin secretion (GSIS) in response to 26.7 mmol/L, compared with 3.3 mmol/L, glucose. After continuous culture or high-passage (MIN-(H)), this GSIS was no longer present and thus represents an excellent model system for investigating beta cell dysfunction. Employing 2-D difference gel electrophoresis and mass spectrometry a panel of protein markers were identified in conditioned media (CM) from MIN-6(L) and MIN-6(H) beta cells. These proteins, including secretogranin II, secretogranin III and transthyretin, are associated with secretory granule biogenesis and were found to have substantially increased levels in the CM from the non-responsive high-passage MIN-6 beta cells. A panel of protein markers found to have increased abundance levels in CM from MIN-6(H) compared with MIN-6(L) beta cells may have the potential to be used clinically for assessing beta cell function and to monitor the effects of specific therapeutics.     

Rapid Identification of Halogen Bonds in Co‐Crystalline Powders via 127I Nuclear Quadrupole Resonance Spectroscopy

¹²⁷I nuclear quadrupole resonance (NQR) spectroscopy is established as a rapid and robust method to indicate the formation of iodine–nitrogen halogen bonds in co‐crystalline powders. Once the relevant spectral frequency range has been established, diagnostic ¹²⁷I NQR spectra can be acquired in seconds. The method is demonstrated for a series of co‐crystals of 1,4‐diiodobenzene. Changes in the ¹²⁷I quadrupolar coupling constant (C_Q) by up to 74.4 MHz correlate with the length of the C?I donor covalent bond and inversely with the I???N halogen‐bond length. The predictive power of this technique is validated on two previously unknown co‐crystalline powders prepared mechanochemically. Single‐crystal growth via co‐sublimation and structure determination by single‐crystal X‐ray diffraction cross‐validates the findings. Natural localized molecular‐orbital analyses provide insight into the origins of the quadrupolar coupling constants.     

Intramolecular Reaction of Transient Phosphenium and Arsenium Ions Giving Rise to Isolable 9‐Phospha‐ and 9‐Arsena‐Fluorenium Ions

Transient phosphenium and arsenium ions, generated by fluoride abstraction from bis(m‐terphenyl)fluoropnictogens, underwent intramolecular electrophilic attack prior to methyl group migration and gave rise to isolable 9‐phospha‐ and 9‐arsena‐fluorenium ions.     

Four cytotoxic N4‐substituted thiosemicarbazones derived from 2‐hydroxynaphthalene‐1‐carboxaldehyde

The X‐ray crystal structures are reported of four novel and potentially O,N,S‐tridentate donor ligands that demonstrate antitumour activity. These ligands are 1‐[(4‐methyl­thio­semicarbazono)methyl]‐2‐naphthol, C₁₃H₁₃N₃OS, (III), 1‐[(4‐ethylthio­semicarbazono)­methyl]‐2‐naphthol, C₁₄H₁₅N₃OS, (IV), 1‐[(4‐phenyl­thio­semicarbazono)­methyl]‐2‐naphthol, C₁₈H₁₅N₃OS, (V), and 1‐[(4,4‐di­methyl­thio­semicarbazono)­methyl]‐2‐naphthol di­methyl sulfoxide solvate, C₁₄H₁₅N₃OS·C₂H₆OS, (VI). These chelators are N4‐substituted thio­semicarbazones, each based on the same parent aldehyde, namely 2‐­zhydroxynaphthalene‐1‐carboxaldehyde isonicotinoylhydrazone. Conformational variations within this series are discussed in relation to the optimum conformation for metal‐ion binding.