Fenton’s reagent-mediated degradation of residual Kraft black liquor

In this work, the effect of Fento’s reagent on the degradation of residual Kraft black liquor was investigated. The effect of Fenton’s reagent on the black liquor degradation was dependent on the concentration of H₂O₂. At low concentrations (5 and 15 mM) of H₂O₂, Fenton’s reagent caused the degradation of phenolic groups (6.8 and 44.8%, respectively), the reduction of reaction medium pH (18.2%), and the polymerization of black liquor lignin. At a high concentration (60 mM) of H₂O₂, Fenton’s reagent induced an extensive degradation of lignin (95–100%) and discoloration of the black liquor. In the presence of traces of iron, the addition of H₂O₂ alone induced mainly lignin fragmentation. In conclusion, Fenton’s reagent and H₂O₂ alone can degrade residual Kraft black liquor under acidic conditions at room temperature.     

Interfacial properties and thermal stability of modified poly(m‐phenylene isophthalamide) thin films

Poly(m‐phenylene isophthalamide) (PMIA) is a resistant to high temperatures and chemically stable engineering material. The application as coatings and membranes, however, is limited by its poor interaction with other materials. In this report, we describe the molecular modification of PMIA through reaction with dimsyl sodium and 2‐iodine‐1‐ethanol. The substitution of 58% of amide hydrogen by ethanol (etOH) groups produces a material (MPMIA) able to develop regularly structured films on silicon substrate. The morphology of the films is dependent on the ionic strength of the precursory solution. MPMIA starts a degradation process by losing the etOH group. MPMIA has a better affinity with poly(p‐cresolformaldehyde) than with a pristine one, increasing the range of composition in which thermal stability and miscibility are observed. Thin films of these blends have different morphologies that vary from nanometric porous to two‐phase microstructured grains, according to the composition. Copyright © 2012 John Wiley & Sons, Ltd.     

Halogenation of the N-Terminus Tyrosine 10 Promotes Supramolecular Stabilization of the Amyloid-β Sequence 7–12

Here, we demonstrate that introduction of halogen atoms at the tyrosine 10 phenol ring of the DSGYEV sequence derived from the flexible amyloid-β N-terminus, promotes its self-assembly in the solid state. In particular, we report the crystal structures of two halogen-modified sequences, which we found to be stabilized in the solid state by halogen-mediated interactions. The structural study is corroborated by Non-Covalent Interaction (NCI) analysis. Our results prove that selective halogenation of an amino acid enhances the supramolecular organization of otherwise unstructured biologically-relevant sequences. This method may develop as a general strategy for stabilizing highly polymorphic peptide regions.     

Convergent synthesis of mosloflavone, negletein and baicalein from crysin

An expeditious synthesis of three polyoxygenated flavones: mosloflavone, negletein and baicalein, starting from crysin, an easily available flavone, by a bromination/methoxylation procedure is reported. The convergent synthesis exploits a base induced Wesley-Moser type rearrangement.     

One-step recursive method for solving systems of differential equations

In this work an iteration one-step method to integrate systems of nonlinear ordinary differential equations with initial values is presented