Design of a new molecule that exhibits observable CD spectra under σ-σ* excitation: 2,6-Disilyl-2,6-disilaspiro[3.3]heptanes

Abstract

We previously designed and prepared the first molecules to exhibit observable CD spectra by n-σ* excitation, 2,6-dithiaspiro[3.3]heptane 2,6-dioxide. Spiro[3.3]heptane frameworks possess axial asymmetry due to puckering of 2 four-membered rings; the ring bonds are rich in p-character due to acute bond angles, which lowers the σ* energy levels. In contrast, the lone pairs are rich in s-character, which results in a good donor with conformational fixation. We expected that, instead of lone pairs as donating orbitals, the use of σ-electron-donating Si-Si bonds should result in UV absorption in the observable range (>180?nm), so that the Cotton effect could appear, at least partially, in that range. We designed 2,6-disilyl-2,6-disilaspiro[3.3]heptanes as models, and performed theoretical calculations to confirm our idea.     

Electrocatalytic Oxidation of Amines on a Mediator‐Modified Electrode by Electrochemical Copolymerization of Nitroxyl Radical Precursor Containing Pyrrole Side Chain and Bithiophene

This paper describes the electrocatalytic oxidation of amines on TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl)‐modified electrodes prepared by electrochemical copolymerization of TEMPO precursor containing pyrrole side chain and 2,2′‐bithiophene. The modified electrode exhibits electrocatalytic activity for the oxidation of primary and secondary amines. Cyclic voltammetric studies showed that the peak current of the cyclic voltammogram increased linearly with increasing concentration of amine in the sample solution.     

Luminescence properties of Tb-activated yttrium gallium garnet phosphors

Comparison of luminescence properties between electron-excited and uv-excited yttrium gallium garnet: Tb phosphors is reported. Although the thermoluminescence and phosphorescence in both cases are quite alike once traps are filled, an apparent difference in the behavior of trap filling has been observed. Small addition of V₂O₃ to these phosphors revealed a unique effect on luminescence properties either with the electron excitation or with the uv excitation.     

Biodegradation of chitin with enzymes and vital components

Chitin from squid pen was effectively degraded by the chitinase from Bacillus sp. PI-7S, while the degradation of chitin with lysozyme proceeded very slowly. Among the various vital components studied, the degradation of chitin from squid pen was performed not by canine serum, canine tela subcutanea, canine tela liver, and equine serum but by bovine serum and caprine serum. Noteworthy is the fact that chitin sponge subcutaneously implanted in dog reported not to have chitinase was degraded in ca. 14 days.     

Cascade reactions in crystals through cation-π-controlled reorientation on exposure to HCl gas

Exposure of 4-azachalcones to HCl gas produced the corresponding HCl salts with a head-to-tail stacked alignment, irradiation of which produced the corresponding syn-HT dimers with high regio- and stereoselectivities, thus showing the effectiveness of the cascade process in crystals.     

Electrical properties of lateral npn junctions using molecular beam epitaxy grown Si-doped GaAs on patterned substrates

We investigated electrical properties of laterally aligned npn junctions formed with one-step molecular beam epitaxial growth of Si-doped GaAs on patterned substrates. Detailed current-voltage (I-V) measurements of the lateral npn junctions showed asymmetric characteristics which suggest that the junction configuration is rather nn⁻pn with a highly compensated n⁻ region than a simple npn configuration. Temperature dependence of the I-V curves was also examined. Cross-sectional electron beam induced current and transmitted electron microscope measurements revealed the critical angle of the crystal plane at which conduction type of Si-doping converts to be exactly 25°, i.e. (311)A plane.     

Influence of cavity de-tuning in semiconductor microcavity LEDs

Data are presented showing the precise role of the cavity de-tuning on the emission properties of semiconductor microcavity light emitting diodes (MC-LEDs). Enhanced output power and narrow line width emission have been observed over a wide range of cavity de-tunings, with a power reduction of less than −1 dB observed for ±12 nm de-tuned devices. For a resonantly de-tuned MC-LED, the slope efficiency extracted from the power output versus current characteristics decreases monotonically with increasing temperature. However, for a MC-LED de-tuned +5.6 nm to long wavelength with respect to the room temperature quantum well (QW) peak, the extracted slope efficiencies vary by less than ±0.5 dB over a temperature range of greater than 65°C. Compared to a conventional LED, narrower beam divergence is observed for MC-LEDs de-tuned to short wavelength with respect to the bare QW peak. For positively de-tuned MC-LEDs the beam divergence broadens, and the far-field emission profiles exhibit a double-lobed pattern that is sensitive to pump level.     

THIOPYRONINE- AND 8-METHOXYPSORALEN-SENSITIZED PHOTODYNAMIC EFFECT ON CELL GROWTH, COLONY FORMING ABILITY and RNA SYNTHESIS IN Saccharomyces MUTANTS DEFICIENT IN DNA REPAIR

Abstract –We compared the photodynamic effects of thiopyronine (TP) and visible light, and 8-methoxypsoralen (8-MOP) and ultraviolet A (UV-A) light, on growth, colony forming ability and RNA synthesis in a repair-proficient Saccharomyces strain and three mutants deficient in DNA repair mechanisms (DNA repair assays). With 8-MOP and UV-A repair-deficient mutants were significantly more sensitive than the repair-proficient strain indicating that the system is sensitive for the detection of DNA damage. With TP and visible light, the photodynamic effects were comparable in the mutants and the control, indicating no DNA damage. These results support previous work showing that the main target of TP photosensitization in eukaryotes is not nuclear DNA.