Studies on the terpenoids and related alicyclic compounds—XXII: Stereochemical study on the angular hydroxylation of polycyclic ketones using benzeneseleninic anhydride

Introduction of an OH group to the tertiary carbon of simple ketones (1, 2 and 6), furanoeremophilane-type ketones (12–19), and tricyclic ketones (20–22) by the use of benzeneseleninic anhydride is described. 10β-Hydroxy compounds were obtained in the case of 12–14 and 20–22. 10α-Hydroxy compounds were obtained in the case of 15 and 16. In the hydroxylation reaction of polycyclic ketones using benzeneseleninic anhydride, the results suggest that the thermodynamically more stable product was usually produced as the major product.     

Flow-injection determination of L-histidine with an immobilized histidine oxidase from Brevibacillus borstelensis KAIT-B-022 and chemiluminescence detection.

A chemiluminometric flow injection analytical system for the quantitation of L-histidine is described. Histidine oxidase (EC 1.4.3.-) from Brevibacillus borstelensis KAIT-B-022 was immobilized on tresylated poly(vinyl alcohol) beads and packed into a stainless-steel column. The hydrogen peroxide produced was detected chemiluminometrically by a flowthrough sensor containing immobilized peroxidase (EC 1.1 1.1.7). The maximum sample throughput was 10 h(-1). The calibration graph was linear from 0.05 to 5 mM; the detection limit (signal to noise ratio = 3) was 0.01 mM. The activity of immobilized histidine oxidase reduced to 65% of the initial value after 350 injections. The system was applied to the determination of L-histidine in fish meat, such as salmon, tunny, bonito, and mackerel.     

Aggregation mechanism of polyglutamine diseases revealed using quantum chemical calculations, fragment molecular orbital calculations, molecular dynamics simulations, and binding free energy calculations

Polyglutamine (polyQ) diseases, including Huntington’s disease (HD), are caused by expansion of polyQ-encoding repeats within otherwise unrelated gene products. The aggregation mechanism of polyQ diseases, the inhibition mechanism of Congo red, and the alleviation mechanism of trehalose were proposed here based on quantum chemical calculations and molecular dynamics simulations. The calculations and simulations revealed the following. The effective molecular bonding is between glutamine (Gln) and Gln (Gln + Gln), between Gln and Congo red (Gln + Congo red), and between Gln and trehalose (Gln + trehalose). The bonding strength is −13.1 kcal/mol for Gln + Gln, −24.4 kcal/mol for Gln + Congo red, and −12.0 kcal/mol for Gln + trehalose. In the polyQ region, both the number of intermolecular Gln + Gln formations and the total calories generated by the Gln + Gln formation are proportional to the number of repetitions of Gln. We propose an aggregation mechanism whose heat generated by the intermolecular Gln + Gln formation causes the pathogeny of polyQ disease. In our aggregation mechanism, this generated heat collapses the host protein and promotes fibrillogenesis. Without contradiction, our mechanism can explain all the experimental results reported to date. Our mechanism can also explain the inhibition mechanism by Congo red as an inhibitor of polyglutamine-induced protein aggregation and the alleviation mechanism by trehalose as an alleviator of that aggregation. The inhibition mechanism by Congo red is explained by the strong interaction with Gln and by the characteristic structure of Congo red.     

A novel clathrate host allowing structural adjustment during the inclusion of 1,2-diaminoethanes

Dimethyl 5-hydroxy-2-oxo-4,5-diphenylcyclopent-3-ene-1,3-dicarboxylate (1a) forms relatively stable inclusion complexes with compounds having 1,2-diaminoethane moiety.     

Atomic correlation between adjacent graphene layers in double-wall carbon nanotubes

Atomic correlation between adjacent graphene layers was elucidated for double-wall carbon nanotubes (DWNTs) through a chiral index assignment of two nested nanotubes by high-resolution transmission electron microscopy. Our analysis provides a rather constant diameter difference close to 0.75 nm but no chiral angle correlation between the constituent nanotubes in the concentric DWNTs. The local atomic correlation as a commensurate graphene stacking was repeatedly found in eccentric DWNTs and circumscribed nanotubes, which should lead to elastic deformation and bundling of nanotubes.     

Straightforward synthesis of fucoxanthin short-chain derivatives via modified-Julia olefination

Fucoxanthin is an essential pigment for the light-harvesting of aquatic algae. It exhibits high energy transfer efficiencies to Chl a (>80%) as well as peridinin (>95%). In order to verify the generality and specificity of the noticeable observation on the ICT excited energy state character, which was found in the study of peridinin, we achieved the straightforward synthesis of a series of fucoxanthin short-chain derivatives via the modified-Julia olefination with the aldehyde half segment possessing a β,γ-epoxyketone function. The established method was successfully applied to the synthesis of the epoxy olefin derivative as an allene modified fucoxanthin analogue.     

Fluorescence Response and Self-Assembly of a Tweezer-Type Synthetic Receptor Triggered by Complexation with Heme and Its Catabolites

There is increasing interest in the development and applications of synthetic receptors that recognize target biomolecules in aqueous media. We have developed a new tweezer-type synthetic receptor that gives a significant fluorescence response upon complexation with heme in aqueous solution at pH 7.4. The synthetic receptor consists of a tweezer-type heme recognition site and sulfo-Cy5 as a hydrophilic fluorophore. The receptor–heme complex exhibits a supramolecular amphiphilic character that facilitates the formation of self-assembled aggregates, and both the tweezer moiety and the sulfo-Cy5 moiety are important for this property. The synthetic receptor also exhibits significant fluorescence responses to biliverdin and bilirubin, but shows very weak fluorescence responses to flavin mononucleotide, folic acid, and nicotinamide adenine dinucleotide, which contain smaller π-scaffolds.     

Strain- and temperature-induced polymorphism of poly(dimethylsiloxane)

Phase behavior of silica-filled poly(dimethylsiloxane) (PDMS) network was investigated by wide-angle X-ray diffraction (WAXD) under various strain ratio between room temperature and ?100 °C, and anomalous polymorphic behavior was discovered. At room temperature, when sufficient strain was applied, PDMS network was found to transform into the mesomorphic phase from which only a pair of sharp equatorial reflections and faint meridional scattering were obtained in the WAXD pattern. At low temperature, PDMS network crystallized into one of three different crystal forms according to strain ratio. These crystal forms were denoted as α, transient, and β forms in the descending order of corresponding strain ratio. The mesomorphic phase at room temperature transformed into the crystalline α form by reducing temperature. There was an anomalous feature about the transition of the crystalline forms that the position of reflections in the WAXD pattern changed continuously and reversibly with strain between the α and the β forms through the transient form, while keeping the diffraction angles almost unchanged.