Production, purification, and characterization of micrococcin GO5, a bacteriocin produced by Micrococcus sp. GO5 isolated from kimchi

Strain GO5, a bacteriocin-producing bacterium, was isolated from green onion kimchi and identified as Micrococcus sp. The bacteriocin, micrococcin GO5, displayed a broad spectrum of inhibitory activity against a variety of pathogenic and nonpathogenic microorganisms, as tested by the spot-on-lawn method; its activity spectrum was almost identical to that of nisin. Micrococcin GO5 was inactivated by trypsin (whereas nisin was not) and was completely stable at 100 degrees C for 30 min and in the pH range of 2.0 to 7.0. Micrococcin GO5 exhibited a typical mode of bactericidal activity against Micrococcus flavus ATCC 10240. It was purified to homogeneity through ammonium sulfate precipitation, ultrafiltration, and CM-Sepharose column chromatography. The molecular mass of micrococcin GO5 was estimated to be about 5.0 kDa by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in situ activity assay with the indicator organism. The amino acid sequence of micrococcin GO5 lacks lanthionine and beta-methyllanthionine and is rich in hydrophobic amino acids and glycine, providing the basis for the high heat stability of this bacteriocin. The N-terminal amino acid sequence of micrococcin GO5 is Lys-Lys-Ser-Phe-Cys-Gln-Lys, and no homology to bacteriocins reported previously was observed in the amino acid composition or N-terminal amino acid sequence. Based on the physicochemical properties, small molecular size, and inhibition of Listeria monocytogenes, micrococcin GO5 has been placed with the class II bacteriocins, but its broad spectrum of activity differs from that of other bacteriocins in this class.     

Enhanced antitumor efficacy of gemcitabine-loaded temperature-sensitive liposome by hyperthermia in tumor-bearing mice

Introduction: Gemcitabine-loaded TSL (Gem-TSL) was used in combination with hyperthermia (HT) to treat the colon adenocarcinoma-bearing BALB/c mice for improved anticancer effect following intravenous administration.

Methods: A new temperature-sensitive liposome (TSL), composed of DPPC:DMPC:DSPC (4:1:1 molar ratio) releasing the encapsulated gemcitabine (Gem) at 41?°C, was developed and evaluated for enhanced antitumor efficacy both in vitro and in vivo.

Results: Drug release from the TSL was sharply increased at 41?°C and in vitro cytotoxicity of Gem-TSL in colon adenocarcinoma cells (CT-26) was 10 times higher than the free drug (IC50?=?0.3?μM versus 3?μM). Apoptosis seemed to be the main mechanism of cell death as the treatment of the cells with Gem-TSL increased the caspse-3/7 activity by 1.5-fold and also caused the fragmentation of chromatin DNA. Gem-TSL suppressed the tumor growth in CT-26-bearing BALB/c mice more stronger than the free gemcitabine after intravenous administration. Moreover, this in vivo antitumor efficacy of Gem-TSL was further increased when HT was added.

Discussion: This study suggests that this new TSL-Gem formulation could serve as a new chemotherapy modality together with HT.     

ZnO nanosphere fabrication using the functionalized polystyrene nanoparticles for dye-sensitized solar cells

The nano-hollow spherical ZnO (NHS ZnO) photoelectrodes were prepared using functionalized polystyrene nanoparticles with flexible dimensional control of the particle diameter for dye-sensitized solar cells applications. NHS ZnO was formed by ZnO nanoparticles that accumulated on the surface of functionalized polystyrene with a high ionic strength. This method represents a one-step preparation method for an inorganic shell via polymerization between ZnO complexes. Even though NHS ZnO has a submicron size, it composed of nanoparticles that connect with each other, thereby implying good electron transfer properties, and has a high surface area. The submicron-sized diameter NHS ZnO has an enhanced light scattering capacity, which promotes the photons with more opportunities to be absorbed by the N719 dye molecules. Therefore, the ZnO films prepared from 600 nm to 1000 nm NHS ZnO possessed higher IPCE values over a wide range (from 400 nm to 750 nm) compared to films of the 300 nm ZnO due to the enhanced light scattering capacities of the film. In photocurrent-voltage measurements, the short-circuit current density of 300 nm and 600 nm NHS ZnO increases from 3.33 mA/cm² to 6.53 mA/cm² while the cell efficiency increases from 1.04% to 3.02% due to the light scattering efficiency. Electrochemical impedance spectroscopy showed that electrons in NHS ZnO with a larger particle size have a longer electron lifetime than NHS ZnO with a smaller particle size, as the latter hinders the electron transport in the NHS ZnO nanostructured films.     

Assessing the digestibility of genetically modified soybean: Physiologically based in vitro digestion and fermentation model

Gastrointestinal digestibility of new proteins inserted in food supply is one of significant parameters for assessing safety of genetically modified (GM) foods on the assumption that digestive stability is undesirable. Digestive stability of GM soybean was evaluated under the physiologically based in vitro digestion model. Electrophoresis was used to follow the in vitro sequential digestions/fermentation procedure and Western blotting was employed to confirm the new protein in GM soybean.CP4EPSPS newly expressed in GM soybean was completely digested in 15 s in the gastric fluid in this model. In the assay of fermentation of new protein, CP4EPSPS was also complete degraded and no fermentation products were found during 24 h of colon fermentation. Results from this study suggested that CP4EPSPS in GM soybean does not have a potential allergenicity due to its complete digestion within a very short time in gastric fluid. No formation of colonic protein fermentation products confirms that new protein is not capable of initiating colon cancer.     

A multi-level capacitor-less memory cell fabricated on a nano-scale strained silicon-on-insulator

A multi-level capacitor-less memory cell was fabricated with a fully depleted n-metal-oxide-semiconductor field-effect transistor on a nano-scale strained silicon channel on insulator (FD sSOI n-MOSFET). The 0.73% biaxial tensile strain in the silicon channel of the FD sSOI n-MOSFET enhanced the effective electron mobility to ～ 1.7 times that with an unstrained silicon channel. This thereby enables both front- and back-gate cell operations, demonstrating eight-level volatile memory-cell operation with a 1 ms retention time and 12 μA memory margin. This is a step toward achieving a terabit volatile memory cell.     

Selective patterning of ZnO nanorods on silicon substrates using nanoimprint lithography

In this research, nanoimprint lithography (NIL) was used for patterning crystalline zinc oxide (ZnO) nanorods on the silicon substrate. To fabricate nano-patterned ZnO nanorods, patterning of an n-octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on SiO₂ substrate was prepared by the polymer mask using NI. The ZnO seed layer was selectively coated only on the hydrophilic SiO₂ surface, not on the hydrophobic OTS SAMs surface. The substrate patterned with the ZnO seed layer was treated with the oxygen plasma to oxidize the silicon surface. It was found that the nucleation and initial growth of the crystalline ZnO were proceeded only on the ZnO seed layer, not on the silicon oxide surface. ZnO photoluminescence spectra showed that ZnO nanorods grown from the seed layer treated with plasma showed lower intensity than those untreated with plasma at 378 nm, but higher intensity at 605 nm. It is indicated that the seed layer treated with plasma produced ZnO nanorods that had a more oxygen vacancy than those grown from seed layer untreated with plasma. Since the oxygen vacancies on ZnO nanorods serve as strong binding sites for absorption of various organic and inorganic molecules. Consequently, a nano-patterning of the crystalline ZnO nanorods grown from the seed layer treated with plasma may give the versatile applications for the electronics devices.     

Inhibitory effect of Zizania latifolia chloroform fraction on allergy-related mediator production in RBL-2H3 cells

Food Science and Biotechnology - Zizania latifolia exhibits anti-inflammatory and anti-allergic effects; however, the mechanisms behind these effects are unknown. Here the ethanol extract of Z....     

Molecular cloning of the genes for GDP-mannose 4, 6-dehydratase and GDP-l-fucose synthetase from Bacteroides thetaiotaomicron

Genes encoding GDP-mannose 4, 6-dehydratase (GMD) and GDP-l-fucose synthetase (GFS) were cloned from Bacteroides thetaiotaomicron and overexpressed in recombinant Escherichia coli by constructing isopropyl-β-d-thiogalactopyranoside (IPTG)-inducible expression vectors. GMD and GFS genes from B. thetaiotaomicron were 60 and 45%, respectively, identical to those from E. coli K12 over their entire lengths. An optimum expression condition of 30oC and 0.1 mM IPTG was chosen for maximum soluble expression of B. thetaiotaomicron GMD and GFS in recombinant E. coli BL21(DE3). Functional expression of B. thetaiotaomicron GMD and GFS in recombinant E. coli strains was confirmed by measuring intracellular GDP-l-fucose content.     

The influence of ceramic surface treatments on the microtensile bond strength of resin cements to Y-TZP ceramic

The effects of surface conditioning methods on the microtensile bond strength of Y-TZP ceramic were studied based on airborne particle abrasion and resin cements.Eight square-shaped(φ12 mm×5 mm high) Y-TZP ceramic were studied blocks(LAVATM,3M ESPE,USA) and flat occlusal dentin blocks were fabricated,pre-treated(airborne abrasion with 125μm Al2O3 particles,tribochemical silica coating with 110 μm Al2O3 particles modified by silica oxide),and bonded to each other using resin cements(Panavia F 2.0,RelyX Unicem).Thereafter the trilayer specimens were cut into microbar specimens with a bonding area of approximately 1.0±0.1 mm2 and then microtensile bond strength tests were performed.The Y-TZP ceramic following airborne particle abrasion with 125μm Al2O3 and silicoating,the surface roughness of Y-TZP and its surface silica content were confirmed to increase.Overall,the Y-TZP ceramic surface treatment with a tribochemical silica coating showed the highest microtensile bond strength of the phosphate monomer-based resin cement to Y-TZP ceramic(mean MPa=18.11±0.27(Panavia F 2.0),17.45±0.39(Rely X Unicem).In cases in which a silica coating was applied,there was no significant difference in the bonding strength depending on resin cements(P0.05).