Self-Assembled Bimetallic Aluminum-Salen Catalyst for the Cyclic Carbonates Synthesis

Bimetallic bis-urea functionalized salen-aluminum catalysts have been developed for cyclic carbonate synthesis from epoxides and CO₂. The urea moiety provides a bimetallic scaffold through hydrogen bonding, which expedites the cyclic carbonate formation reaction under mild reaction conditions. The turnover frequency (TOF) of the bis-urea salen Al catalyst is three times higher than that of a μ-oxo-bridged catalyst, and 13 times higher than that of a monomeric salen aluminum catalyst. The bimetallic reaction pathway is suggested based on urea additive studies and kinetic studies. Additionally, the X-ray crystal structure of a bis-urea salen Ni complex supports the self-assembly of the bis-urea salen metal complex through hydrogen bonding.     

Growth Inhibition and Induction of Stress Protein,GroEL, of <Emphasis Type="Italic">Bacillus cereus</Emphasis> Exposed to Antibacterial Peptide Isolated from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> SC-8

This study was conducted to investigate the antibacterial effect of BSAP-254 on Bacillus cereus with the induced stress proteins. The BSAP-254 is an antimicrobial peptide isolated from soybean-fermenting bacteria, Bacillus subtilis SC-8. It had a narrow spectrum of activity against B. cereus group. The growth inhibitory effect of BSAP-254 (50 μg/mL) reduced the population of B. cereus from >10⁸ to 10⁴ colony-forming units per milliliter within 30 min. In B. cereus exposed to BSAP-254, 14 intracellular proteins were differentially expressed as determined by 2-DE coupled with MS. Of the differentially expressed proteins identified, the stress protein GroEL, which is heat shock protein, was induced in B. cereus exposed to antibacterial peptide.     

Two-dimensionally self-arranged protein nanoarrays on diblock copolymer templates

Novel methods for creating protein arrays with two-dimensional control can significantly enhance basic biological research as well as various bioarray applications. We demonstrate that the structural variety and chemical heterogeneity of self-assembled, hexagonal polystyrene-b-poly(vinylpyridine) micelles can be successfully exploited as templates for easy and rapid fabrication of functional protein arrays over a large scale. Spontaneous formation of such polymeric template-guided protein molecules yields high-density protein arrays that exhibit repeat spacings in a nanoscopic dimension. The ensuing self-assembled protein molecules in the array maintain their natural conformation and activity over a very long time period. By tuning the size of the underlying block copolymer templates, our amphiphilic diblock copolymer-based approach to create high-density protein patterns also permits spatial control over two-dimensional repeat spacings of protein nanoarrays. These unique advantages of polystyrene-b-poly(vinylpyridine) templates make the spontaneously constructed protein nanoarrays highly suitable as functional protein sensor substrates. Therefore, our novel two-dimensional protein assembly method can be greatly beneficial for high-throughput proteomic assays and multiplexed high-density protein sensing applications.     

Mass production of methane from food wastes with concomitant wastewater treatment

We developed a process for production of methane at a pilot scale. This process consists of three stages. The first stage is a semianaerobic hydrolysis/acidogenic step in which organic wastes are converted to various sugars, amino acids, and volatile fatty acids (VFAs). Operation temperature and pH were 45°C, and 5.0–5.5, respectively. Hydraulic retention time (HRT) was 2 d. To remove the putrid odor and to enhance the hydrolysis of organic wastes, a mixture of bacteria isolated from landfill soil was inoculated into the reactor. Total chemical oxygen demand (tCOD) and biological oxygen demand (BOD) were 36,000 mg/L and 40,000 mg/L, respectively. The second stage was an anaerobic acidogenic process, which can produce large amount of VFAs including acetate, propionate, butyrate, valerate, and caproate. Operation temperature and pH were 35°C, and 5.0–5.5, respectively. HRT was 2 d. The third stage was a strictly anaerobic methane fermentation step producing methane and carbon dioxide from VFAs. The working volume of upflow anaerobic sludge blanket (UASB) type reactor was 1200 L, and operation temperature and pH were 41°C, and 7.7–7.9, respectively. HRT was 12 d. Seventy two percent of methane at maximum was generated and the yield was 0.45–0.50 m³/kg VS of food wastes. Through the process, 88% of tCOD and 95% of BOD were removed. The wastewater was treated with the biological aerobic and anaerobic filters immobilized with heterotrophic and autotrophic nitrifying and denitrifying bacteria. Ninety percent of total nitrogen (T-N) was removed by this treatment. The residual T-N and total phosphorous (T-P) were removed by the algal periphyton treatment system. The final concentrations of nitrogen and phosphorous in the drain water were 53 and 7 mg/L, respectively.     

New high-energy luminescence bands from Co2+ in ZnSe

Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co²⁺_Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed.     

Efficient synthesis of enantiomerically pure 2-acylaziridines: Facile syntheses of N-Boc-safingol, N-Boc-D-erythro-sphinganine, and N-Boc-spisulosine from a common intermediate

Various enantiomerically pure 2-acylaziridines were prepared efficiently from the corresponding aziridine-2-carboxylate via Weinreb's amide and the subsequent treatment of organometallic compounds. The carbonyl group of those 2-acylaziridines was stereoselectively reduced by NaBH4in the presence of ZnCl2 to give erythro-1,2-amino alcohols with high diastereoselectivities and chemical yields. Using this methodology, we prepared (1R,2S)-N-Boc-norephedrine 5, N-Boc-safingol 8, N-Boc-D-erythro-sphinganine 9, and N-Boc-spisulosine 10 in high yields.     

Nanoscale protein patterning using self-assembled diblock copolymers

Novel methods for immobilizing proteins on surfaces have the potential to impact basic biological research as well as various biochip applications. Here, we demonstrate a unique method to pattern proteins with a nanometer periodicity on silicon oxide substrates using microphase-separated diblock copolymer thin films. We developed a straightforward and effective protein immobilization technique using the microphase-separated domains of polystyrene-block-poly(methyl methacrylate) to localize various model protein molecules such as bovine immunoglobulin G, fluorescein isothiocyanate conjugated anti-bovine immunoglobulin G, and protein G. The self-organizing nature of the diblock copolymer was exploited to produce periodically alternating, nanometer-spaced polymeric domains exposing the two chemical compositions of the diblock to surface. We demonstrate that the model proteins selectively self-organize themselves on the microdomain regions of specific polymer components due to their preferential interactions with one of the two polymer segments. This diblock copolymer-based, self-assembly approach represents a step forward for facile, nanometer-spaced protein immobilization with high areal density and could provide a pathway to high-throughput proteomic arrays and biosensors.