Structure of ultrahigh-molecular-weight polyethylene in the solid state as studied by variable-temperature 13C CP/MAS NMR spectroscopy

In order to obtain some insight into the structure of an ultrahigh-molecular-weight polyethylene sample, ¹³C CP/MAS NMR experiments have been carried out at temperatures from 23 to ?108°C. The peak for the crystalline component moves upfield with a decrease in temperature, which is contrary to what was reported previously for a melt-crystallized polyethylene sample. On the basis of x-ray diffraction results and quantum-chemical calculations, it is suggested that the methylene carbons are in the distorted orthorhombic form at low temperatures.     

Asymmetric total synthesis of rhinacanthin A

Starting from a reduced lapachol compound, the total synthesis of rhinacanthin A in both racemic and enantioenriched forms is achieved in eight steps without forming any undesired β-lapachone derivatives. For the synthesis of enantioenriched rhinacanthin A, the introduction of the asymmetric center was carried out by using the catalytic asymmetric epoxidation of an unfunctional trisubstituted olefin using Shi’s epoxidation diketal catalyst. The acidic treatment of a derived enantioenriched epoxynaphthol and the following CAN oxidation afforded the target molecule with high enantiomeric purity.     

Synthesis of polyhedral particles by dispersion polymerization in supercritical carbon dioxide

The novel synthesis of polyhedral particles was attained by the dispersion polymerization of styrene in supercritical carbon dioxide using a polydimethylsiloxane-based macroazoinitiator as a precursor of the surfactant. The macroazoinitiator, VPS-1001, composed of poly(dimethylsiloxane) and 6-8 molecules of the azo groups served as a precursor of the surfactant for the dispersion polymerization by azobisisobutylonitrile as an initiator to produce 0.8-4 μm polyhedral particles. The size of the particles decreased as a result of increasing the VPS-1001 concentration. Too high a concentration of VPS-1001 caused coagulation of the particles. A decrease in the temperature increased the particle size and size distribution, while a decrease in the pressure produced particles with nonspecific shapes. An increase in the stirring rotation speed tended to increase the size and size distribution. However, too high a speed of rotation also caused coagulation of the particles.     

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Pipette tip biosensors for bacterial double-stranded DNA using bioluminescence induced by zinc finger luciferase

The authors describe a pipette type of biosensor for detecting target genes and using a zinc finger protein fused to luciferase (ZF luciferase). The ZF protein binds to a specific DNA sequence, and the target double-stranded (ds) DNA can be detected by monitoring the enzymatic activity of ZF luciferase. A small avidin-immobilized reaction plate is placed on a plastic pipette tip (referred to as Biologi tip). The dsDNA detection procedures are carried out by using a programmable dispensing robot equipped with a photodetector. These procedures include (a) the aspiration of an analyte to capture the biotinylated target dsDNA (a product of a polymerase chain reaction) on the small reaction plate inside the pipette tip, (b) the introduction of ZF luciferase and luciferin into the pipette tip, and (c) migration of the pipette tip to the detection port to measure bioluminescence on the small reaction plate. The emission originating from luciferase activity is observed on the reaction plate containing immobilized biotin-tagged target dsDNA, whereas plates containing non-target or biotinylated single-stranded DNA only do not yield a signal. The intensity of emission increases proportionally to the concentration of dsDNA, and the detection limit of the target dsDNA is as low as 62 pM. An actual genomic DNA sample from Escherichia coli O157 was successfully detected by this automatic analyzer using the Biologi tip equipped with a reaction plate. This indicates that this system has a large potential for practical applications, including in particular point-of-care analyses in hygiene control, food safety testing, and clinical diagnosis.

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Graphical abstract A pipette-type biosensor was developed to detect target genes using a luciferase-fused zinc finger protein, where a small NeutrAvidin-immobilized reaction plate was placed on the tip, and the biotinylated target double-stranded DNA was detected by monitoring the bound luciferase activity.

     

Morphological change of crystalline polymer films by annealing: substrate‐ and heating/cooling‐rate‐dependent surface roughness

We study the morphological change of crystalline polymer films by annealing using atomic force microscope, X‐ray diffraction, and Fourier transform infrared spectroscopy techniques. As typical samples, we employ high‐density and low‐density polyethylene films prepared by the cast method. After annealing at 135 °C for 4 h, the surface roughness of polyethylene films by the atomic force microscope significantly increases, and the crystallite size by the X‐ray diffraction also shows some increase, while the Fourier transform infrared spectroscopy spectrum hardly exhibits any change. This can be well explained as a result of the growth of crystal structure by recrystallization during annealing. More interestingly, we find that the choice of the substrate and also the heating/cooling rates for annealing significantly influences the surface roughness of the films. Copyright © 2017 John Wiley & Sons, Ltd.