Confinement in carbon nanospace-induced production of KI nanocrystals of high-pressure phase

An outstanding compression function for materials preparation exhibited by nanospaces of single-walled carbon nanohorns (SWCNHs) was studied using the B1-to-B2 solid phase transition of KI crystals at 1.9 GPa. High-resolution transmission electron microscopy and synchrotron X-ray diffraction examinations provided evidence that KI nanocrystals doped in the nanotube spaces of SWCNHs at pressures below 0.1 MPa had the super-high-pressure B2 phase structure, which is induced at pressures above 1.9 GPa in bulk KI crystals. This finding of the supercompression function of the carbon nanotubular spaces can lead to the development of a new compression-free route to precious materials whose syntheses require the application of high pressure.     

Shedding light on hidden reaction pathways in radical polymerization by a porous coordination network

A coordination network comprising 2-vinyltriphenylene was treated with AIBN at a high temperature, but the radical polymerization of the vinyl monomer was completely suppressed by spatial separation and otherwise hidden aerobic oxidation pathways are enhanced.     

Microscopic Studies of 2H-NbSe2 Probed by Positive Muon

Abstract

The microscopic state of the positively charged light particle in the transition metal dichalcogenide 2H-NbSe₂ was studied using the muon spin relaxation method (μ⁺SR) and muon level crossing resonance method (μ-LCR). Muons are expected to stay at interlayer position and behaves as a hydrogen like intercalant. We discuss the relation between conduction electron properties and the muon's behavior.     

Quantitative comparison of a corona-charged aerosol detector and an evaporative light-scattering detector for the analysis of a synthetic polymer by supercritical fluid chromatography

A corona-charged aerosol detector (CAD) was developed to improve the sensitivity, reproducibility and quantitativeness of detection as compared to evaporative light-scattering detector (ELSD) for liquid chromatography. Our laboratory used the corona CAD as a detector for supercritical fluid chromatography (SFC) and evaluated its performance compared to the ELSD by using a certified reference material of poly(ethylene glycol) (PEG) and a well-defined equimass mixture of uniform PEG oligomers. The corona CAD was able to detect a 10 times more dilute solution of uniform oligomers compared to the ELSD. Although the original data of molecular mass by ELSD was 4.6% smaller than the certified value of PEG 1000, molecular mass distribution obtained by corona CAD was virtually almost the same as the certified value without any calibrations.     

The promiscuity of beta-strand pairing allows for rational design of beta-sheet face inversion

Recent studies suggest the dominant role of main-chain H-bond formation in specifying beta-sheet topology. Its essentially sequence-independent nature implies a large degree of freedom in designing beta-sheet-based nanomaterials. Here we show rational design of beta-sheet face inversions by incremental deletions of beta-strands from the single-layer beta-sheet of Borrelia outer surface protein A. We show that a beta-sheet structure can be maintained when a large number of native contacts are removed and that one can design large-scale conformational transitions of a beta-sheet such as face inversion by exploiting the promiscuity of strand-strand interactions. High-resolution X-ray crystal structures confirmed the success of the design and supported the importance of main-chain H-bonds in determining beta-sheet topology. This work suggests a simple but effective strategy for designing and controlling nanomaterials based on beta-rich peptide self-assemblies.     

A new homostilbene and two new homoisoflavones from the bulbs of Scilla scilloides

A new homostilbene, named scillabene A (2), and two new homoisoflavones, named scillavones A (3) and B (4), were isolated from the bulbs of Scilla scilloides DRUCE (Liliaceae) along with 13 known compounds comprising a homostilbene, seven homoisoflavones, a xanthone, a lignan, and three nortriterpenes. The structures of 2-4 were characterized as 3,5,4'-trihydroxy-3'-methoxy-4-methyl-trans-stilbene, (3R)-5,7,2'-trihydroxy-3',4'-dimethoxyspiro{2H-1-benzopyran-7'-bicyclo[4,2,0]octa[1,3,5]-trien}-4-one and (3S)-3-(3,4-dihydroxybenzyl)-5-hydroxy-6,7-dimethoxychroman-4-one, respectively, on the basis of spectroscopic data and X-ray crystallographic analysis.     

Use of stable carbon isotope ratios to determine the source of cypermethrin in so-called natural plant extract formulations used for organic farming

Some natural plant extract formulations (NPEFs, also referred to as essential oils) used in organic farming have been shown to contain synthetic pesticides. We obtained samples of four NPEFs (Muso, Hekiro, Kensogen-Ten, and Nurse Green) that were contaminated with the synthetic pyrethroid cypermethrin, and we used gas chromatography coupled with combustion, cryofocusing, and isotope ratio mass spectrometry to determine the stable carbon isotope ratios (δ¹³C) for the cypermethrin in the four NPEF samples, as well as in ten cypermethrin reagents and two commercial pesticide formulations (Agrothrin emulsion and Agrothrin water-dispersible powder). Our goal was to identify the source of the cypermethrin in the NPEFs. Cryofocusing markedly sharpened the cypermethrin peak and thus improved the accuracy and precision of the determined δ¹³C values. The δ¹³C values (±?SD) of the 16 cypermethrin samples ranged from ?28.3?±?0.2 to ?24.5?±?0.2?‰. Surprisingly, the four NPEFs showed similar δ¹³C values (?26.8 to ?27.3?‰), suggesting that the cypermethrin in all the samples came from the same source (either the same chemical reaction or the same primary material). This possibility was supported by previously published results. In addition, the δ¹³C values of the two commercial pesticides were similar to the values for the NPEFs, suggesting that the commercial pesticides had been diluted and sold as NPEFs.     

Fluctuating Carbonaceous Networks with a Persistent Molecular Shape: A Saddle‐Shaped Geodesic Framework of 1,3,5‐Trisubstituted Benzene (Phenine)

A saddle‐shaped macromolecule has been synthesized. The molecule was designed as a geodesic saddle with 1,3,5‐trisubstituted benzene (named phenine) as the fundamental unit. The phenines were woven into a polygonal framework that was composed of 168 sp²‐hybridized carbon atoms. The saddle‐shaped structure with unique symmetry showed atypical conformational changes. The biaryl linkages in this molecule had a small energy barrier for rotation, and these structural fluctuations resulted in seven ¹H NMR resonances representing 84 aromatic hydrogen atoms. Nevertheless, the overall saddle shape of the molecule was persistent, and the “up” and “down” orientations of phenine moieties circulated to give average ¹H resonances. The structural characteristics of this molecule, including the anomalous entropy‐driven dimerization, may deepen our understanding of defect‐rich graphitic sheets.     

Synthesis of dl-coriolin

The total synthesis of dl-coriolin has been achieved in a stereoselective way. The key tricyclic intermediate was synthesized from dicyclopentadiene through a route which involved an S_N2 reaction at a neopentylic position.     

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.