Leishmanicidal active withanolides from a pakistani medicinal plant, Withania coagulans

In the course of screening for leishmanicidal constituents from Asian and South American medicinal plants, a Pakistani medicinal plant, Withania coagulans, showed activity. We therefore studied the active components of the methanol extract of aerial parts of W. coagulans. From the ethyl acetate soluble fraction of the extract, four new withanolides (1-4) were isolated along with seven known withanolides (5-11). The new compounds were elucidated to be (14R,15R,17S,20S,22R)-14,15,17,20-tetrahydroxy-1-oxowitha-2,5,24-trienolide (1), (14R,15R,17S,20S,22R)-14,15,17,20-tetrahydroxy-1-oxowitha-3,5,24-trienolide (2), (14S,17R,20S,22R)-14,17,20-trihydroxy-1-oxowitha-2,5,24-trienolide (3), and (14S,17R,20S,22R)-14,17,20-trihydroxy-1-oxowitha-3,5,24-trienolide (4), from 1H-NMR, 13C-NMR, 2D-NMR and high resolution (HR)-MS data. Some of these compounds having the partial structure 1-oxo-2,5-diene showed strong leishmanicidal activity against Leishmania major.     

Challenge to detect 1,4-zwitterions spectroscopically in a ketene-alkene reaction

The first example of direct spectroscopic detection of transient species, 1,4-zwitterions, generated in a ketene-alkene reaction is reported. Also, a striking result of the intervention of an unprecedented "1,4-zwitterion neutral dimer" is presented in a new mechanistic pathway; the ketene-alkene reaction gives the product cyclobutanone from the initial cycloadduct alpha-methyleneoxetane.     

Hybridization Assay by Time-Resolved Capillary Gel Electrophoresis with a Lanthanide Chelate

Capillary electrophoresis of crude biological samples with time-resolved fluorescence (TRF) detection enables elimination of interference from organic fluorophores and from light scattering. Because the fluorescence lifetime of biological substances and impurities overlaps the fluorescence lifetime of conventional labeling dyes, TRF detection with conventional organic labeling dyes suffers from background fluorescence. In this work, we synthesized a luminescent lanthanide chelating reagent to covalently bind the 5′-end of DNA through its dichroic functional group while retaining the unique luminescent properties of the lanthanide chelate, i.e. large Stokes shift, sharp emission, and a long luminescence lifetime in the microsecond to millisecond range. The luminescence of lanthanide chelates is inherently quenched by dissociation of the central metals in typical biological buffers containing a strong chelator, for example EDTA or phosphate; the synthesized Eu³⁺ chelate reagent, however, was stable even in EDTA solutions. In addition to stability in biological buffer solution, the synthesized Eu³⁺ chelate reagent enabled direct labeling of single-stranded oligonucleotides, and was used for DNA hybridization assay by time-resolved capillary gel electrophoresis. DNA hybridization assay in fetal bovine serum was also demonstrated.     

Temperature- and field-dependent energy transfer in CdSe nanocrystal aggregates studied by magneto-photoluminescence spectroscopy

The influence of temperature and applied magnetic fields on photoluminescence (PL) emission and electronic energy transfer (ET) of both isolated and aggregated CdSe nanocrystals was investigated. Following 400-nm excitation, temperature-dependent, intensity-integrated and energy-resolved PL measurements were used to quantify the emission wavelength and amplitude of isolated CdSe nanocrystals. The results indicated an approximately three-fold increase in PL intensity upon decreasing the temperature from 300 K to 6 K; this was attributed to a reduction of charge carrier access to nanocrystal surface trap states and suppression of thermal loss channels. Temperature-dependent PL measurements of aggregated CdSe nanocrystals, which included both energy-donating and -accepting particles, were analyzed using a modified version of F?rster theory. Temperature-dependent ET efficiency increased from 0.55 to 0.75 upon decreasing the sample temperature from 225 K to 6 K, and the ET data contained the same trend observed for the PL of isolated nanoclusters. The application of magnetic fields to increase nanocrystal ET efficiency was studied using magneto-photoluminescence measurements recorded at a sample temperature of 1.6 K. We demonstrated that the exciton fine structure population of the donor was varied using applied magnetic fields, which in turn dictated the PL yield and the resultant ET efficiency of the CdSe nanocrystal aggregate system. The experimental data indicated an ET efficiency enhancement of approximately 7%, which was limited by the random orientation of the spherical nanocrystals in the thin film.     

Novel antiviral fucoidan from sporophyll of Undaria pinnatifida (Mekabu)

Structural characterization and antiviral activities of fucoidan from sporophyll of Undaria pinnatifida (Mekabu) was examined. The fucoidan was composed of fucose and galactose with an approximately ratio of 1.0:1.1. Degree of substitution of sulfate was 0.72 and its apparent molecular weight was 9,000. Methylation analyses showed that fucoidan had various sugar linkages, and revealed that the fucoidan might have complicated structure. This fucoidan showed potent antiviral activities against herpes simplex virus type 1 (HSV-1), HSV-2, and human cytomegalovirus.     

Micro-channel fabrication by femtosecond laser to arrange neuronal cells on multi-electrode arrays

The surface of a single-crystal germanium wafer was transformed to crystals of germanium fluorides and oxides upon exposure to a vapor of HF and HNO₃ chemical mixture. Structure analysis indicates that the transformation results in a germanate polycrystalline layer consisting of germanium oxide and ammonium fluogermanate with preferential crystal growth orientation in 〈101〉 direction. Local vibrational mode analysis confirms the presence of N–H and Ge–F vibrational modes in addition to Ge–O stretching modes. Energy dispersive studies reveal the presence of hexagonal α-phase GeO₂ crystal clusters and ammonium fluogermanates around these clusters in addition to a surface oxide layer. Electronic band structure as probed by ellipsometry has been associated with the germanium oxide crystals and disorder-induced band tailing effects at the interface of the germanate layer and the bulk Ge wafer. The acid vapor exposure causes Ge surface to emit yellow photoluminescence at room temperature.     

A new ring-opening access to aeroplysinin-1, a secondary metabolite of Verongia aerophoba

An improved synthetic methodology of spiroisoxazolines by employing anodic oxidation of the corresponding phenol derivative has been established. An alternative efficient synthesis of aeroplysinin-1 1 has been achieved by employing the ring-opening reaction of spiroisoxazolines 10b, 10c as a key step.     

Large two-photon absorption (TPA) cross-section of directly linked fused diporphyrins

The excited state dynamics and two-photon absorption properties of four novel triply linked porphyrin dimers in toluene have been investigated. The fused porphyrin dimers exhibit extremely increased two-photon absorption cross-section values (12,000-15,000 GM) compared with porphyrin monomers owing to much enhanced pi-electron delocalization throughout the porphyrin dimer ring.     

Direct determination of a topmost atomic layer of (100) surfaces on (La0.3Sr0.7)(Al0.65Ta0.35)O3 single crystals annealed in air by high-resolution scanning transmission electron microscopy

Herein, we investigated the surface of an (La_0.3Sr_0.7)(Al_0.65Ta_0.35)O₃ (LSAT) single crystal via scanning transmission electron microscopy (STEM) after annealing in air. We found amorphous mounds and atomically flat surfaces formed on the surface of the (100) LSAT single crystal subsequent to heat treatment. These surface mounds mainly constituted SrO, including ~50 at.% Al. The atomically flat surface showed a B-site termination determined by the direct surface observation at the atomic scale through HAADF-STEM. The atomic arrangements on the surface were accommodated by surface-mound formation and La evaporation. Consequently, the ordered structure disappeared because of the increase in the Ta content at the terminated B-site layer.