Photoelectrochemical Enhancement of Cu2O by a Cu2Te Hole Transmission Interlayer.

Cuprous oxide (Cu2O) films are electrodeposited on fluorinated tin oxide (FTO) substrates with controlled crystallographic orientation and optimized film thickness. The Cu2O films exhibit a (100)-to-(111) texture change and a pyramid-to-cuboidal crystallite morphology transformation by increasing the electrodeposition current density. The cuboidal crystallites enclosed by (100) sidewalls and (111) truncated surfaces demonstrate better photoelectrochemical property than the pyramid crystallites. By introducing a copper(I) telluride (Cu2Te) layer in between Cu2O and FTO, the photocurrent density increases 70% for the (111)-textured Cu2O film in a 1 M Na2SO4 solution under AM1.5 G illumination. The enhancement is mainly attributed to the improved separation of photocarriers in the illuminated Cu2O film by pumping hole carriers to the Cu2Te layer. In contrast to typical electron pathway management, this study provides an alternative route to improve the photoelectrochemical performance of Cu2O-based photocathodes through hole pathway modification.

Gomphocarpus mosaic virus, a distinctive member of the genus Potyvirus.

Plants of the species Gomphocarpus physocarpus, commonly known as balloon plant or swan plant, exhibiting virus-like symptoms of mosaic, mottle and crinkling were observed and collected in the southwestern part of Taiwan in 2015. Electron microscopic examination showed the presence of virus-like flexuous-rod particles. Potyvirus pinwheel-shape and laminated inclusion bodies were observed in the preparations of ultrathin sections of diseased leaves. The complete genome sequence of the potyvirus of balloon plant was determined. It is 9998 nucleotides in length, excluding the 3'-terminal poly(A) tail. It contains two open reading frames encoding a polyprotein of 3196 amino acids and a PIPO protein of 89 amino acids. The polyprotein gene shares 52.8-68.4% nucleotide sequence identity and 40.2-75.8% amino acid sequence identity with other potyviruses tested. Molecular analysis indicates that the virus is most closely related to but distinct from keunjorong mosaic virus (KjMV). The virus causing mosaic, mottle and crinkling on Gomphocarpus plants (gomphocarpus mosaic virus, GoMV) likely belongs to a new species of the genus Potyvirus.

8.13 µm in length and CMOS compatible polarization beam splitter based on an asymmetrical directional coupler.

A compact silicon polarization beam splitter (PBS) is proposed based on an asymmetrical directional coupler consisting of a wide waveguide and a dielectric loaded narrow waveguide. Given that TE and TM polarizations are the dominant mode in the wide and narrow waveguides, respectively, a perfect phase-matching condition in the TM mode but a huge phase mismatching in the TE mode can be achieved. Therefore, the TE mode is almost uncoupled regardless of device length but the TM mode can only completely couple to the cross port at an appropriate coupling length. An ultrashort (∼8.13 µm long) PBS is designed based on a silicon-on-insulator nanowire with a loading refractive index of 2.0 and a gap width of 200 nm. Numerical simulations show that the proposed PBS has a broad bandwidth (∼100 nm) with large extinction ratio (>10 dB) and low insertion loss (<0.61 dB). The fabrication-error tolerance of the PBS is also discussed.

Ultra-compact, high-Q silicon microdisk reflectors.

We demonstrate wavelength-selective reflectors based on silicon microdisk resonators integrated with compact Y-branch splitters, using a CMOS-photonics technology. A high quality factor (Q) of ~ 88,000 was measured in the reflection spectrum for a 2.5-µm-radius device with a small footprint of 6 × 17 µm(2) and a wide free-spectral range (FSR) of over 41 nm. As the radius is reduced to 1.5 µm, corresponding to a device footprint of 4 × 15 µm(2), the spectrum shows an ultra-wide FSR of over 71 nm with the compromise of having a reduced Q of ~ 4000. The coupling between a microdisk and a waveguide is numerically investigated. We further propose a multichannel sensing system using cascaded microdisk reflectors.

Diterpene cyclases and the nature of the isoprene fold.

The structures and mechanism of action of many terpene cyclases are known, but no structures of diterpene cyclases have yet been reported. Here, we propose structural models based on bioinformatics, site-directed mutagenesis, domain swapping, enzyme inhibition, and spectroscopy that help explain the nature of diterpene cyclase structure, function, and evolution. Bacterial diterpene cyclases contain approximately 20 alpha-helices and the same conserved "QW" and DxDD motifs as in triterpene cyclases, indicating the presence of a betagamma barrel structure. Plant diterpene cyclases have a similar catalytic motif and betagamma-domain structure together with a third, alpha-domain, forming an alphabetagamma structure, and in H(+)-initiated cyclases, there is an EDxxD-like Mg(2+)/diphosphate binding motif located in the gamma-domain. The results support a new view of terpene cyclase structure and function and suggest evolution from ancient (betagamma) bacterial triterpene cyclases to (betagamma) bacterial and thence to (alphabetagamma) plant diterpene cyclases.

Lipophilic bisphosphonates as dual farnesyl/geranylgeranyl diphosphate synthase inhibitors: an X-ray and NMR investigation.

Considerable effort has focused on the development of selective protein farnesyl transferase (FTase) and protein geranylgeranyl transferase (GGTase) inhibitors as cancer chemotherapeutics. Here, we report a new strategy for anticancer therapeutic agents involving inhibition of farnesyl diphosphate synthase (FPPS) and geranylgeranyl diphosphate synthase (GGPPS), the two enzymes upstream of FTase and GGTase, by lipophilic bisphosphonates. Due to dual site targeting and decreased polarity, the compounds have activities far greater than do current bisphosphonate drugs in inhibiting tumor cell growth and invasiveness, both in vitro and in vivo. We explore how these compounds inhibit cell growth and how cell activity can be predicted based on enzyme inhibition data, and using X-ray diffraction, solid state NMR, and isothermal titration calorimetry, we show how these compounds bind to FPPS and/or GGPPS.

Bisphosphonate inhibition of a Plasmodium farnesyl diphosphate synthase and a general method for predicting cell-based activity from enzyme data.

We screened 26 bisphosphonates against a farnesyl diphosphate synthase from Plasmodium vivax, finding a poor correlation between enzyme and cell growth inhibition (R(2) = 0.06). To better predict cell activity data, we then used a combinatorial descriptor search in which pIC(50)(cell) = a pIC(50)(enzyme) + bB + cC + d, where B and C are descriptors (such as SlogP), and a-d are coefficients. R(2) increased from 0.01 to 0.74 (for a leave-two-out test set of 26 predictions). The method was then further validated using data for nine other systems, including bacterial, viral, and mammalian cell systems. On average, experimental/predicted cell pIC(50) correlations increased from R(2) = 0.28 (for an enzyme-only test set) to 0.70 (for enzyme plus two descriptor test set predictions), while predictions based on scrambled cell activity had no predictive value (R(2) = 0.13). These results are of interest since they represent a general way to predict cell from enzyme inhibition data, with in three cases, R(2) values increasing from approximately 0.02 to 0.72.