Highly reproducible secondary electron imaging under electron irradiation using high-pass energy filtering in low-voltage scanning electron microscopy

The reproducibility of contrast in secondary electron (SE) imaging during continuous electron irradiation, which caused surface contamination, was investigated using SE high-pass energy filtering in low-voltage scanning electron microscopy (SEM). According to high-pass energy-filtered imaging, dopant contrast in an indium phosphide remained remarkably stable during continuous electron irradiation although the contrast in unfiltered SE images decreased rapidly as a contamination layer was formed. Charge neutralization and the SE energy distributions indicate that the contamination layer induces a positive charge. This results in a decrease of low-energy SE emissions and reduced dopant contrast in unfiltered SE images. The retention of contrast was also observed in high-pass energy-filtered images of a gold surface. These results suggest that this imaging method can be widely used when SE intensities decrease under continuous electron irradiation in unfiltered SE images. Thus, high-pass energy-filtered SE imaging will be of a great assistance for SEM users in the reproducibility of contrast such as a quantitative dopant mapping in semiconductors.     

Multinuclear Cu-catalysts based on SPINOL-PHOS in asymmetric conjugate addition of organozinc reagents

Multinuclear Cu/Zn complex-catalyzed efficient asymmetric conjugate addition of organozinc reagents to acyclic and cyclic enones has been developed in the presence of a wide variety of regioisomeric chiral diols bearing phosphorus moieties as ligands. The regioisomeric SPINOL-PHOS ligands based on a SPINOL architecture showed an unexpected inversion of stereoselectivity.     

Determination of histamine in seafood by hydrophilic interaction chromatography/tandem mass spectrometry

A simple method was developed to determine histamine, an important compound in chemical food poisoning, by extraction followed by hydrophilic interaction chromatography-tandem mass spectrometry using a hydrophilic column with sulfobetaine-type zwitterion groups. The quantitation range in seafood products was from 0.4 to 200 mg kg(-1) for 5 g food samples. Quantitative recoveries were obtained with four types of seafood product. These results agreed well with those from the more complex, conventional HPLC method, which requires sample derivatization with dansyl chloride.     

Amycolamicin: A Novel Broad‐Spectrum Antibiotic Inhibiting Bacterial Topoisomerase

The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X‐ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans‐decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad‐spectrum antibiotic against Gram‐positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors.     

Aqueous synthesis of single-crystalline ZnO prisms on graphite substrates

Morphological change from ZnO films to ZnO prisms is achieved by an electrochemical deposition method on a graphite substrate at the low temperature of 70 °C. The ZnO prisms, which are prism-shaped ZnO rods with a wide diameter, have hexagonal well-defined crystallographic facets. The ZnO prism is 1.4 μm in diameter and 1.3 μm in length. Transmission electron microscopy and electron diffraction patterns indicate that the ZnO prisms have a single-crystalline wurtzite structure with c-axis orientation. Additionally, cathodoluminescence shows that the annealed ZnO prisms in nitrogen gas emit a significant level of near-band-edge ultraviolet light.     

Asteropine A, a sialidase-inhibiting conotoxin-like peptide from the marine sponge Asteropus simplex

Marine sponges contain structurally intriguing and biologically active peptides of nonribosomal peptide synthase origin, often containing amino acids with novel structures. Here we report the discovery of asteropine A (APA), a cystine knot to be isolated from marine sponges. The solution structure of APA as determined by NMR belongs to the four-loop class of cystine knots similar to those of some conotoxins and spider toxins. However, the highly negatively charged surface of APA is uncommon among other cystine knots. APA competitively inhibits bacterial sialidases, but not a viral sialidase. APA was inactive against all other enzymes tested and did not have any apparent antitumor activity. Our data suggest that APA and other knotting peptides may be important leads for antibacterial and even antiviral drug development.     

Catalytic asymmetric mannich-type reactions activated by ZnF2 chiral diamine in aqueous media

Catalytic asymmetric Mannich-type reactions of an alpha-hydrazono ester with silicon enolates in aqueous media have been developed by using ZnF2 and chiral diamines as catalysts. In these reactions, both Zn2+ and a fluoride anion were necessary to achieve high yields and enantioselectivities, suggesting a double activation mechanism, in which Zn2+ activates the alpha-hydrazono ester and the fluoride anion simultaneously activates the silicon enolate. When chiral diamine ligands bearing methoxy-substituted aromatic rings were employed, the reactions in aqueous THF were markedly accelerated. Furthermore, the use of these diamines facilitated the asymmetric Mannich-type reactions in water without any organic cosolvents. It is noteworthy that either syn or anti adducts were stereospecifically obtained from (E)- or (Z)-silicon enolates, respectively. Interestingly, these reactions proceeded smoothly only in the presence of water. On the basis of several experimental results, it can be concluded that the reaction mechanism is likely to be a fluoride-catalyzed one, in which the ZnF2 chiral diamine complex is regenerated from the Me3SiF formed during the reaction.     

Order to disorder optical phase transition in random photonic crystals

Transition process of optical modal properties induced by the introduction of randomness into random photonic crystals is investigated by a computational method. We analyze an impulse response of two-dimensional triangular photonic crystals, in which the positions of the air holes are slightly deviated to random directions. It is shown that the appropriate degree of random departure from a perfect crystal state gives rise to multiple scattering of low group velocity band-edge modes and supports their strong Anderson localization. The achieved confinement efficiency of light exceeds the one obtained in the perfect photonic crystal state.     

Evolution of two-step structural phase transition in Fe1+dTe detected by low-temperature x-ray diffraction

The low-temperature crystal structure of Fe_1.13Te, which exhibits an anomalous two-step magnetic transition, was clarified by the systematic x-ray diffraction measurements. It was found that two-step structural phase transition, tetragonal–orthorhombic–monoclinic, occurred correspondingly to the two-step magnetic transition. The detailed analysis of the profile at 5 K indicated the coexistence of the minor orthorhombic area inside the major, monoclinic lattice, which could explain the lower-shift (suppression) of the antiferromagnetic transition temperature in Fe_1.13Te and suggest a possibility of superconductivity at the domain boundary.     

Polarity Directed Appraisal of Pharmacological Potential and HPLC-DAD Based Phytochemical Profiling of Polygonum glabrum Willd

The present study was designed to evaluate polarity-dependent extraction efficiency and pharmacological profiling of Polygonum glabrum Willd. Crude extracts of leaves, roots, stems, and seeds, prepared from solvents of varying polarities, were subjected to phytochemical, antioxidant, antibacterial, antifungal, antidiabetic, and cytotoxicity assays. Maximum extraction yield (20.0% w/w) was observed in the case of an acetone:methanol (AC:M) root extract. Distilled water:methanol (W:M) leaves extract showed maximum phenolic contents. Maximum flavonoid content and free radical scavenging potential were found in methanolic (M) seed extract. HPLC-DAD quantification displayed the manifestation of substantial quantities of quercetin, rutin, gallic acid, quercetin, catechin, and kaempferol in various extracts. The highest ascorbic acid equivalent total antioxidant capacity and reducing power potential was found in distilled water roots and W:M leaf extracts, respectively. Chloroform (C) seeds extract produced a maximum zone of inhibition against Salmonella typhimurium. Promising protein kinase inhibition and antifungal activity against Mucor sp. were demonstrated by C leaf extract. AC:M leaves extract exhibited significant cytotoxic capability against brine shrimp larvae and α-amylase inhibition. Present results suggest that the nature of pharmacological responses depends upon the polarity of extraction solvents and parts of the plant used. P. glabrum can be considered as a potential candidate for the isolation of bioactive compounds with profound therapeutic importance.