Synthesis, structure, and reaction of 1-alkynyl(aryl)-lambda3-bromanes

Reported here for the first time are the synthesis, structure, and reaction of hypervalent 1-alkynyl(aryl)-lambda3-bromanes. BF3-catalyzed ligand exchange on bromine(III) of p-trifluoromethylphenyl(difluoro)-lambda3-bromane with 1-alkynyl(trimethyl)stannanes in dichloromethane at -78 degrees C afforded 1-alkynyl(aryl)-lambda3-bromanes in good yields. Trimethyl(trimethylsilylethynyl)stannane gave silylethynyl-lambda3-bromane selectively. 13C NMR chemical shifts of acetylenic carbon atoms of alkynylbromanes are compared with those of alkynyl-lambda3-iodanes and explained in terms of the spin-orbit-induced heavy atom effects. The structure of tert-butylethynylbromane was established by a single-crystal X-ray analysis of its crown ether complex. The 1-alkynyl(aryl)-lambda3-bromanes serve as highly electron-deficient Michael acceptors and undergo tandem Michael-carbene rearrangements by the reaction with sulfonate anions, yielding 1-alkynyl sulfonates.     

Interaction between poly[(R)-3-hydroxybutyrate] depolymerase and biodegradable polyesters evaluated by atomic force microscopy

Adsorption of PHB depolymerase from Ralstonia pickettii T1 to biodegradable polyesters such as poly[(R)-3-hydroxybutyrate] (PHB) and poly(l-lactic acid) (PLLA) was investigated by atomic force microscopy (AFM). The substrate-binding domain (SBD) with histidines within the N-terminus was prepared and immobilized on the AFM tip surface via a self-assembled monolayer with a nitrilotriacetic acid group. Using the functionalized AFM tips, the force-distance measurements for polyesters were carried out at room temperature in a buffer solution. In the case of AFM tips with immobilized SBD and their interaction with polyesters, multiple pull-off events were frequently recognized in the retraction curves. The single rupture force was estimated at approximately 100 pN for both PLLA and PHB. The multiple pull-off events were recognized even in the presence of a surfactant, which will prevent nonspecific interactions, but reduced when using polyethylene instead of polyesters as a substrate. The present results provide that the PHB depolymerase adsorbs specifically to the surfaces of polyesters and that the single unbinding event evaluated here is mainly associated with the interaction between one molecule of SBD and the polymer surface.     

Binding of anthraquinone dyes by polyion complexes consisting of a piperidinium cationic polymer and various polyanions in aqueous solution

The extent of binding of 1-amino-4-alkylaminoanthraquinone-2-sulfonates (alkyl?methyl, ethyl, propyl, and butyl), which have different chemical structures from methyl orange derivatives, by polyion complexes consisting of a piperidinium cationic polymer and various polyanions such as sodium poly acrylate, poly methacrylate, poly styrenesulfonate, carboxymethylcellulose, and dextran sulfate, was measured in an aqueous solution. The effect of alkyl group of the anthraquinone dye on the binding behavior was investigated. Also, the resultant binding characteristics were compared with those previously observed with methyl orange and its homologs. These polyion complexes exhibited very strong binding affinity toward the anthraquinone dye. The polyion complex of the polycation and sodium poly styrenesulfonate bound the dye noncooperatively and the binding process was athermal. The first binding constant accompanying the binding is of the order of 10⁵–10⁶. In contrast, the polyion complexes composed of the polycation and the other polyanions exhibited strong cooperative binding and the binding process was exothermic. The possible mode of binding is discussed.     

Three-dimensional high-performance liquid chromatography based on time-resolved laser fluorimetry

Microcolumn high-performance liquid chromatography is used for trace determinations of polynuclear aromatic hydrocarbons. The detector is a laser fluorimetric system with subnanosecond time resolution. The detection limit is 210 fg for perylene. In chromatography, the fluorescence decay curves are measured successively as the sample elutes by a microcomputer-controlled data-processing system. A three-dimensional chromatogram, in which retention times and delay times are displayed, is constructed after sample elution. A real sample extracted from airborne particulates is measured, and perylene, benzo(a)pyrene, and benzo(ghi)perylene are shown to be present.     

Finding market structure by sales count dynamics—Multivariate structural time series models with hierarchical structure for count data—

In this paper, we propose a multivariate time series model for sales count data. Based on the fact that setting an independent Poisson distribution to each brand’s sales produces the Poisson distribution for their total number, characterized as market sales, and then, conditional on market sales, the brand sales follow a multinomial distribution, we first extend this Poisson–multinomial modeling to a dynamic model in terms of a generalized linear model. We further extend the model to contain nesting hierarchical structures in order to apply it to find the market structure in the field of marketing. As an application using point of sales time series in a store, we compare several possible hypotheses on market structure and choose the most plausible structure by using several model selection criteria, including in-sample fit, out-of-sample forecasting errors, and information criterion.     

Thermally switchable polyrotaxane as a model of stimuli-responsive supramolecules for nano-scale devices

A polyrotaxane consisting of many β-cyclodextrins (β-CDs) and a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) capped with bulky end-groups was synthesized as a model of stimuli-responsive supramolecules for nanoscale devices. The polyrotaxane was reversibly soluble-insoluble in water in response to temperature. This was achieved through the assembled and dispersed states of β-CDs along the block copolymer. It is considered that intermolecular hydrogen bondings of β-CDs, as well as the PEG segment length of the copoloymer, are predominant factors for regulating such thermally switchable behavior of the polyrotaxane.     

Supramolecular network formation through inclusion complexation of an α‐cyclodextrin‐based molecular tube

The supramolecular network formation through inclusion complexation between α‐cyclodextrin‐based molecular tube (MT) and poly(ethylene oxide) monocetylether‐graft‐dextran (5C₁₆PEO‐g‐Dex40) was demonstrated. From isothermal titration calorimetric (ITC) measurement, it was confirmed that MT formed an inclusion complex with two C₁₆PEO side chains in 5C₁₆PEO‐g‐Dex40. From viscosity measurements, the specific viscosity of the solution containing MT and 5C₁₆PEO‐g‐Dex40 was much larger than that containing 5C₁₆PEO‐g‐Dex40. It is considered that MT participates in the supramolecular network formation of 5C₁₆PEO‐g‐Dex40 through inclusion complexation with two C₁₆PEOs grafted to independent Dex40s.