"Cation pool" method based on C-C bond dissociation. Effective generation of monocations and dications

The "cation pools" of alkoxyarylcarbenium ions were effectively generated by the oxidative C-C bond dissociation using low temperature electrolysis. The present method is especially effective for the generation and accumulation of dications, which react with carbon nucleophiles.     

Giant reduction in dynamic modulus of kappa-carrageenan magnetic gels

Effects of magnetization on the complex modulus of kappa-carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer, kappa-carrageenan, and a ferrimagnetic particle, barium ferrite. The complex modulus was measured before and after magnetization of the gel by dynamic viscoelastic measurements with a compressional strain. The gels showed a giant reduction in the storage modulus of approximately 10(7) Pa and also in the loss modulus of approximately 10(6) Pa due to magnetization. The reduction increased with increasing volume fraction of ferrite, and it was nearly independent of the frequency. It was also found that the change in the modulus was nearly independent of the magnetization direction and irradiation time of the magnetic fields to the gel. The magnetic gels demonstrating the giant reduction in the dynamic modulus showed a large nonlinear viscoelastic response. It was observed that the magnetic gel was deformed slightly due to magnetization. The observed giant complex modulus reduction could be attributed to the nonlinear viscoelasticity and deformation caused by magnetization. Magnetism, nonlinear viscoelasticity, and effects of magnetization on the morphological and shape changes were discussed.     

Fluorometric determination of sugars using fluorescein-labeled concanavalin A–glycogen conjugates

The fluorescence of fluoresceinisothiocyanate-labeled concanavalin A (FITC-Con A) was quenched by forming an FITC-Con A–glycogen conjugate and dequenched upon addition of sugars to the conjugate solution due to disaggregation of the conjugate. However, fluorescence quenching was barely observed upon formation of FITC-Con A–dextran conjugate. The sugar-induced fluorescence response of the FITC-Con A–glycogen conjugate depended significantly on the type of sugar: methylated α-D-glucose and α-D-mannose both induced high and rapid responses, while the responses to D-mannose and D-glucose were moderate. In contrast, no response was observed in the presence of D-galactose due to a lack of affinity to Con A. Thus, it is apparent that D-glucose and other sugars can be detected via the fluorescence of the FITC-Con A–glycogen conjugate.      

Electrochemical SNPs detection using an abasic site-containing DNA on a gold electrode

An abasic site-containing DNA combined with lumiflavin allows amperometric determination of single nucleotide polymorphism through hydrogen bond-mediated nucleobase recognition in water by using abasic sites as a molecular recognition field.     

Recent insights into iron homeostasis and their application in graminaceous crops

Higher plants utilize various mechanisms to maintain iron homeostasis. To acquire sparingly soluble iron from the rhizosphere, graminaceous plants synthesize natural iron (III) chelators known as mugineic acid family phytosiderophores (MAs). Recent research has uncovered various genes involved in iron uptake and translocation, as well as factors regulating the expression of these genes, especially in rice. Manipulation of these molecular components is used to produce transgenic crops with enhanced tolerance to iron deficiency, or with a high seed iron content. Since iron homeostasis is closely linked to that of other mineral elements, an understanding of this phenomenon will serve as the basis for the production of crops with low concentrations of toxic metals and transgenic plants for phytoremediation.     

TiCl4 induced anti-Markovnikov rearrangement

Stereoisomeric bicyclic tert-alcohols afforded identical ring-expansion products via cationic anti-Markovnikov rearrangement from perpendicular tert-cations into identical six-membered ring secondary cations by the treatment with TiCl4. These results provide evidence that the reaction takes place by the cationic stepwise mechanism. [reaction: see text]     

High pressure organic chemistry; XV. Non-catalyzed cleavage reaction of ethers with acyl halides

Abstract

A variety of cyclic and acyclic ethers are efficiently reacted with acyl chlorides or acyl bromides to afford the ether-cleaved compounds of ω-chloro-or ω-bromoesters under high pressure conditions. The reactivity of ethers is found to be roughly depend on the basicity of the ether oxygen atom.     

Non‐Thermoresponsive Decanano‐sized Domains in Thermoresponsive Hydrogel Microspheres Revealed by Temperature‐Controlled High‐Speed Atomic Force Microscopy

Despite the tremendous efforts devoted to the structural analysis of hydrogel microspheres (microgels), many details of their structures remain unclear. Reported in this study is that thermoresponsive poly(N‐isopropyl acrylamide) (pNIPAm)‐based microgels exhibit not only the widely accepted core–shell structures, but also inhomogeneous decanano‐sized non‐thermoresponsive spherical domains within their dense cores, which was revealed by temperature‐controlled high‐speed atomic force microscopy (TC‐HS‐AFM). Based on a series of experiments, it is concluded that the non‐thermoresponsive domains are characteristic for pNIPAm microgels synthesized by precipitation polymerization, and plausible structures for microgels prepared by other polymerization techniques are proposed.