The synthesis and properties of a methylviologen analogue

A novel derivative of methylviologen, prepared by transannular reaction of [2.2] (3,5) pyridinophane, shows large bathochromic shift in the electronic spectrum and nearly equal redox potential compared with methylviologen.     

Optimally designed layer formation for wavelength-selective photodetectors based on grating-assisted coupling

Wavelength-selective photodetectors employing vertically grating-coupled optical filters are designed with a straightforward waveguide structure in order to improve wavelength selectivity. By arranging stacked layer formation for the absorption layer, we can greatly reduce the cross-talk absorption from unselected light down to -40 dB while keeping high selective absorption efficiency. Such photodetectors with a weighted coupling-assisted grating achieve an excellent bandpass filter-detector response which shows a steep transition between stopband and passband.     

The work function reduction of the Pt field emitter

We have carried out the field emission experiments to measure the temperature dependence of the work function of Pt field emitter and found that the work function steeply decreases more than 2 eV by annealing at relatively low temperature above about 500 K in ultra high vacuum. The maximum reduction of the work function was 2.59 eV. The reduced work function was restored the original value of Pt clean surface by applying high voltage of only 20% of Pt evaporation field. The experimental results are tentatively interpreted in terms of the formation of complex cyanides on the emitter shank during the electrochemical etching in KCN solution and the surface diffusion of potassium atoms formed by the thermal decomposition of the complex cyanides to the emitter cap.     

Chromatographic Removal of Host Cell DNA from Cellular Products Using Columns Packed with Cationic Copolymer Beads

This paper describes a method for selective removal of DNA from various cellular products using columns packed with cross-linked poly(ethyleneimine) (PEI) beads or cross-linked N,N-dimethylaminopropylacrylamide (DMAPAA) beads. Each bead type showed a high DNA-adsorbing activity under experimental conditions of pH 5.0–9.0 and ionic strength of μ = 0.05–0.4. When γ-globulin was present in solution with DNA under physiological conditions (pH 7.2, μ = 0.17), DNA-removing activity of PEI columns was unsatisfactory because both the DNA and the γ-globulin were adsorbed onto the column. In contrast, DMAPAA columns allowed removal of DNA from various protein solutions contaminated with DNA. DNA concentration in each treated protein solution was below 10 ng mL^?1, and high recovery of proteins was obtained.     

Selective removal of DNA from protein solution with copolymer particles derived from N,N-dimethylaminopropylacrylamide

To remove nucleic acids from cellular products as drugs, cross-linked N,N-dimethylaminopropylacrylamide (DMP) particles with cationic functional groups were prepared. The particle's hydrophobicity and its anion-exchange capacity were easily adjusted by changing the cross-linking agent and the DMP ratio in the cross-linking, respectively. When divinylbenzene (DVB) was used as a cross-linking agent and the DMP ratio (in the cross-linking) was adjusted to 90 mol%, the particles (DMP-DVB, 90:10) showed the highest adsorbing activity of DNA (salmon spermary). Its adsorption capacity was 54 mg/ml adsorbent. On the other hand, the adsorption of bovine serum albumin (BSA) to the DMP-DVB extremely increased with increase in the adsorbent's pore size (molecular mass exclusions; M(lim)) from 2 x 10(3) to 1 x 10(4), but decreased with increase in the buffer's ionic strength (mu) to 0.2 or stronger. As a result, when the DMP-DVB (80:20) with M(lim) 2 x 10(3) was used as adsorbent by a column method at pH, 7.2 and mu = 0.17, it only selectively removed DNA from a BSA solution, including 1000 microg/ml of BSA and 10 microg/ml of DNA. The adsorbent decreased the concentration of DNA in the BSA solution to < 10 ng/ml, and the recovery rate of BSA was more 98%.     

pH-dependent behavior of surface-immobilized artificial leucine zipper proteins

The coiled-coil protein motif occurs in over 200 proteins and has generated interest for a range of applications requiring surface immobilization of the constituent peptides. This paper describes an investigation of the environment-responsive behavior of a monolayer of surface-immobilized artificial proteins, which are known to assemble to form coiled-coil structures in bulk solution. An extended version of the quartz crystal microbalance (QCM-D) and surface plasmon resonance (SPR) are independently employed to characterize the adsorption of the proteins to a gold surface. The data suggest that the molecules arrange in a closely packed layer orientated perpendicular to the surface. QCM-D measurements are also employed to measure pH-induced changes in the resonant frequency (f) and the energy dissipation factor (D) of a gold-coated quartz crystal functionalized with the formed monolayer. Exposure of the protein monolayer to a pH 4.5 solution results in a shift of 43 Hz in f and a shift of -0.7 x 10(-6) in D as compared to pH 7.4. In contrast, increasing the pH to 11.2, results in f and D shifts of -17 Hz and 0.6 x 10(-6), respectively. The magnitude of the observed shifts suggests that the proteins form a rigid layer at low pH that can be hydrated to a fluid layer as the pH is increased. These observations correlate with spectroscopic changes that indicate a reduction in the helical content of the protein in bulk solutions of high pH.     

Catalytic degradation of polyolefins over hexagonal mesoporous silica: Effect of aluminum addition

Degradations of polypropylene (PP) and polyethylene (PE) over pure hexagonal mesoporous silica and aluminum-containing hexagonal mesoporous silica catalysts were studied in a fixed bed catalytic reactor at 380 and 430 °C, respectively. The thermal and catalytic degradations of both PP and PE in liquid-phase-contact and vapor-phase-contact modes over pure hexagonal mesoporous silica had no significant effect on the product yields. The liquid products were widely distributed in hydrocarbons with boiling point ranges of 36–405 °C. By adding a small amount of aluminum to the hexagonal mesoporous material, aluminium-containing hexagonal mesoporous silica exhibited good performance in cracking heavy molecular weight hydrocarbons into light hydrocarbons. High liquid yields and less coke deposits were obtained in liquid-phase-contact reaction with increasing aluminum content. The liquid products were mainly composed of C₅–C₁₀ hydrocarbons with boiling points of 36–174 °C, and propene, butene, and butane were main components in gaseous products. The effect of degradation temperature was not observed on product yields though degradation rate of polyolefin into liquid products was faster. Conversely, in vapor-phase-contact reaction, an increase in gaseous yield was observed when increasing the amount of aluminum and temperature of the cracking reactor, while the residue yield remained constant.     

A new electronic transition found for the aniline derivatives

From comparisons of the ultraviolet absorption spectra of aniline derivatives in the gas phase with those in solutions, it is here proposed that there is a transition from the ground state to a molecular Rydberg state between the first and second π-type transitions.