Syntheses and optical properties of <Emphasis Type="Italic">α</Emphasis>- and <Emphasis Type="Italic">β</Emphasis>-cyano-poly(<Emphasis Type="Italic">p</Emphasis>-phenylene vinylene) derivatives

Two light emitting molecules with the cyano group at different positions on the vinylene i.e., 2,5-bis(2-thienyl-1-cyanovinyl)-1-(2_-ethylhexyloxy)-4-methoxybenzene (-TPT) and 2,5-bis(2-thienyl-2-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene (-TPT), and corresponding polymers, i.e., poly[2,5-bis(2-thienyl-1-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene] (denoted as P1) and poly[2,5-bis(2-ethienyl-2-cyanovinyl)-1-(2-ethylhexyloxy)-4-methoxybenzene] (denoted as P2) were synthesized. -TPT and -TPT, respectively, were blended into two host polymers, poly(methyl methacrylate (PMMA) and poly(9-vinylcarbazole) (PVK), to study the optical properties of the dopants in different host polymer matrices. Although -TPT and -TPT have the same backbone structure, their optical properties are much different. The PL emission maximum ( _max) of -TPT was found blue-shifted, compared with that of -TPT, while the PL intensity of -TPT was stronger than that of -TPT. Concentration effect in the optical properties was found, 1 wt% of -TPT in PVK had the maximum fluorescent emission.The PL maximum peak wavelengths for polymer films (P1 and P2) were found red-shifted; while their PL intensities were weaker when compared with those of blends.     

Dynamic-mechanical behavior of polyethylenes and ethene/<Emphasis Type="Italic">α</Emphasis>-olefin-copolymers: Part II. <Emphasis Type="Italic">α</Emphasis>- and <Emphasis Type="Italic">β</Emphasis>-relaxation

Several ethylene homopolymers and ethene/ α-olefin-copolymers with crystallinities ranging between 85 and 12% were characterized by dynamic-mechanical measurements. The occurring relaxations were correlated to the crystallinity of the polymeric materials and to morphology. The α-relaxation, being attributed to interlamellar shear, was found to be around 60 °C with activation energies of about 120 kJ/mol in samples with more than 42% crystallinity. The β-transition shows a much greater variety among the different samples characterized. Its relaxation temperatures vary between −40 and 10 °C with activation energies between 200 and 400 kJ/mol. The α- and β-relaxation of several quenched samples with crystallinities between 63 and 42% were found to overlap, thus producing bimodal maxima and different activation energies from the Arrhenius plots. A separation of these overlapping relaxations was only possible by measuring the relaxations over a frequency range of more than three orders of magnitude.     

A novel ∈-lysine acylase from <Emphasis Type="Italic">Streptomyces mobaraensis</Emphasis> for synthesis of <Emphasis Type="Italic">N∈</Emphasis>-acyl-<Emphasis Type="SmallCaps">l</Emphasis>-lysines

A novel ∈-lysine acylase (N ₆-acyl-l-lysine amidohydrolase; EC 3.5.1.17) was isolated from Streptomyces mobaraensis and purified to homogeneity by SDS-PAGE from the culture broth. The purified enzyme was monomeric, with a molecular mass of approximately 60 kDa. The enzyme was inactivated by the presence of 1,10-phenanthroline and activated in the presence of Co²⁺ and Zn²⁺. The enzyme showed a pH optimum of 8.0 and was stable at temperatures of up to 50°C for 1 h at pH 8.0. The enzyme specifically catalyzed the hydrolysis of the amide bond of various N∈-acyl-l-lysines. Furthermore, the enzyme efficiently catalyzed the synthesis of N∈-acyl-l-lysines with fatty and aromatic acyl groups in an aqueous buffer. In the syntheses of N∈-decanoyl-l-lysine, N∈-lauroyl-l-lysine, and N∈-myristoyl-l-lysine, the product precipitated and the yield was 90% or higher using 10 mM FA and 0.5 M l-lysine as the substrate.     

Enhanced <Emphasis Type="Italic">β</Emphasis>-carotene production by <Emphasis Type="Italic">Rhodotorula glutinis</Emphasis> using high hydrostatic pressure

High hydrostatic pressure (HHP) technology was used for improving the ability of β-carotene biosynthesis of Rhodotorula glutinis R68. After the treatments of five repeated cycles at 300 MPa for 15 min, the barotolerant mutant PR68 was obtained. After 72 h of culture, the biomass of mutant PR68 was 21.6 g/L, decreased by 8.5% compared to the parent strain R68, but its β-carotene production reached 19.4 mg/L, increased by 52.8% compared to the parent strain R68. The result of restriction fragment length polymorphism analysis suggested that mutant strain PR68 was likely to change in nucleic acid level, and thus enhanced β-carotene production in this strain was a result of gene mutation induced by HHP treatment. HHP technology seems a promising approach for improving industrial microbes.     

Dynamic-mechanical behavior of polyethylenes and ethene-/<Emphasis Type="Italic">α</Emphasis>-olefin-copolymers: Part III. <Emphasis Type="Italic">γ</Emphasis>-relaxation

The temperature- and frequency-dependent dynamic-mechanical properties in the temperature regime of the γ-transition were determined for a number of polyethylenes and ethylene/α-olefin-copolymers differing in their crystallinity and crystal morphology. The temperature dependence of the γ-transition was found to obey the Arrhenius law for thermally activated processes. The γ-transition temperature determined at a frequency of 1 Hz and the corresponding activation energy were analyzed as a function of the crystallinity. As an overall trend, both quantities are found to decrease with decreasing crystallinity, which is explained by the increase in free volume due to the incorporation of short-chain branches or the thermal pretreatment (e.g., quenching). Taking into account that the crystal morphology of polyethylenes can be classified into four different groups, a more detailed picture appears. Within one type of morphology both quantities, namely the transition temperature and the activation energy, increase with decreasing crystallinity independent of the α-olefin used as the comonomer. These findings can be explained by partial orientations of the molecule segments in the interlamellar amorphous space in the case of HDPE or by the increased steric hindrance of the crankshaft motion by the short-chain branches. From the findings of this series of studies, it was concluded that the glass transition in polyethylene and polyethylene/α-olefin-copolymers is the β- and not the γ-transition.     

Effect of <Emphasis Type="Italic">β</Emphasis>-Cyclodextrin on <Emphasis Type="Italic">trans</Emphasis> Fats,CLA, PUFA and Phospholipids of Milk Fat

The aim of this study was to evaluate the effect of β-cyclodextrin (β-CD) on trans C18:1 fatty acid isomers, conjugated linoleic acid (CLA), polyunsaturated fatty acids (PUFA) and phospholipids in pasteurized milk. The individual trans C18:1 isomers were not significantly affected by the β-CD. trans-11 C18:1 (vaccenic acid) was found to be the major isomer (1.31 ± 0.12%) followed by trans-15 C18:1 (0.35 ± 0.06%). Individual trans linoleic acids did not show differences from the effect of β-CD, representing the high amount of the isomer trans-11 cis-15 C18:2 (0.433 ± 0.087%). The main CLA isomer cis-9 trans-11 C18:2 (rumenic acid) did not show differences between the control milk (0.672 ± 0.080%) and β-CD milk (0.663 ± 0.074%). PUFA and omega-3 and -6 fatty acids were not also significant by the effect of β-CD. Total phospholipids were not significantly affected by effect of the β-CD (0.023 ± 0.001% vs. 0.022 ± 0.001%). β-CD is a effective oligosaccharide for cholesterol removal from pasteurized milk and does not significantly affect the lipid components of the milk fat.     

Variation of Insect Attracting Odor in Endophytic <Emphasis Type="Italic">Epichloë</Emphasis> Fungi: Phylogenetic Constrains <Emphasis Type="Italic">Versus</Emphasis> Host Influence

Odor is a key trait for pollinator attraction in flowering plants, and many studies have investigated odor evolution in the light of pollinator selection by emphasizing the importance of the plant phylogenetic history. By contrast, little is known on the evolution of odors in fungus–insect interactions. In this study, profiles of three volatile compounds that are emitted by grass-inhabiting Epichloë fungi (Clavicipitaceae, Ascomycota) and that have a confirmed or likely role in the attraction of gamete-transferring Botanophila flies were investigated. We collected headspace samples from stromata of six European Epichloë species (including various host races) that originated from different locations in Switzerland, France, Poland, and UK for conducting gas chromatography analyses. Odor profiles exhibited considerable variation, but profiles of most species overlapped and did not discriminate at the species level. The exception was Epichloë festucae, which had a profile dominated by methyl (Z)-3-methyldodec-2-enoate. Based on an Epichloë phylogeny, there was some hierarchical structuring regarding levels of chokol K, another confirmed Botanophila attractant. However, patterns of odor profiles appeared to be largely dependant on particular Epichloë–host associations. The observed variation may be the result of complex selective pressures imposed by Botanophila gametic vectors, local environment, and mycoparasites.     

Dual stimuli-responsive supramolecular polymeric nanoparticles based on poly(<Emphasis Type="Italic">α</Emphasis>-cyclodextrin) and acetal-modified <Emphasis Type="Italic">β</Emphasis>-cyclodextrin-azobenzene

To aim at pH environment in tumor tissue and light-controlled drug release, UV and pH dual-responsive supramolecular polymeric nanoparticles mediated by host-guest interactions of poly(α-cyclodextrin) and acetal-modified β-cyclodextrin-azobenzene were developed in this work. The host molecule was poly(α-cyclodextrin) and the guest molecule was composed of acetal-modified β-cyclodextrin with one azobenzene linked. The inclusion of α-cyclodextrin and azobenzene leaded to amphiphilic supramolecular polymer, which further self-assembled to form supramolecular polymeric nanoparticles in aqueous medium. UV and pH responsiveness of supramolecular polymeric nanoparticles attributed to azobenzene and acetal, respectively. Supramolecular polymeric nanoparticles based on poly(α-cyclodextrin) and acetal-modified β-cyclodextrin-azobenzene with the average diameter of sub-100 nm were controllable to release the drugs regulated by pH and UV.     

Cellulose–<Emphasis Type="Italic">co</Emphasis>-polyacrylonitrile blends: Properties of combined solutions in <Emphasis Type="Italic">N</Emphasis>-metylmorpholine-<Emphasis Type="Italic">N</Emphasis>-oxide and the formation and thermolysis of composite fibers

Combined solutions of cellulose and an acrylonitrile-based copolymer in N-methylmorpholine-N-oxide have been prepared for the first time, new composite fibers have been formed, and the properties of the solutions and fibers under standard conditions and during thermal treatment have been studied. On the basis of studying the phase state and morphological peculiarities of combined cellulose solutions with polyacrylonitrile additives, it has been shown that the completed solutions make emulsions in the entire range of investigated concentrations. The rheological behavior of combined solutions changes with temperature. With the use of IR spectroscopy methods, it has been found that the addition of polyacrylonitrile to cellulose results in the association of nitrile groups with hydroxyl groups of cellulose, which favors the cyclization of CN groups during heating and the appearance of polyconjugated bonds in polyacrylonitrile chains. Thermal transformations of cellulose and polyacrylonitrile in the course of mixed-fiber carbonization have been studied via DSC and TGA. It has been shown that polyacrylonitrile inhibits the dehydration processes in cellulose and reduces the intensity of the peak due to the first stage of the structural rearrangement, i.e., acts as a “catalyst” of pyrolysis.     

Nystatin Interferes with the Effects of <Emphasis Type="Italic">N</Emphasis>-Methyl-<Emphasis Type="Italic">N</Emphasis>′-nitro-<Emphasis Type="Italic">N</Emphasis>-nitrosoguanidine on Sphingolipid Metabolism in Human FL Cells

Previously we have shown that an alkylating agent N-methyl-N'-nitro-N- nitrosoguanidine (MNNG) can induce receptor clustering and the activation of a downstream signal molecule NF-kappaB, and that the receptor clustering is associated with changes in sphingolipids metabolism. On the other hand, the polyene antibiotic nystatin can block MNNG-induced receptor clustering. In this study, using a lipidomic approach, we further evaluated whether nystatin influenced the effects of MNNG on sphingolipids metabolism. It was found that nystatin itself induced changes in the sphingolipids profile in human amnion FL cells to a certain extent, including an increase or decrease of some sphingolipid species. Interestingly, nystatin can block, at least partially, the changes of sphingolipids-induced by MNNG. In addition, nystatin can also partially inhibit the activation of NF-kappaB induced by MNNG. Neither MNNG nor nystatin affects the mRNA levels of serine palmitoyltransferase, acid sphingomyelinase (ASM), and sphingomyelin synthase, key enzymes in the sphingolipids biosynthesis pathway. However, MNNG can activate ASM and neutral sphingomyelinase, while nystatin preincubation inhibits the activation. Taken together, these data suggested that nystatin interferes with the effects of MNNG, and might elicit its function through altered sphingolipids metabolism.     

Hepatic Lipase Gene −514<Emphasis Type="Italic">C</Emphasis>/<Emphasis Type="Italic">T</Emphasis> Polymorphism in the Guangxi Hei Yi Zhuang and Han Populations

Hei Yi Zhuang is an isolated subgroup of the Zhuang minority in China. This study was designed to compare the difference in the hepatic lipase gene (LIPC) -514C/T polymorphism and its association with lipid profiles between the Guangxi Hei Yi Zhuang and Han populations. Genotyping of the LIPC -514C/T was performed in 873 subjects of Hei Yi Zhuang and 867 participants of Han Chinese. The frequency of -514T allele was 43.47% in Hei Yi Zhuang, and 36.10% in Han (P < 0.001). The frequencies of CC, CT and TT genotypes were 30.01, 53.04 and 16.95% in Hei Yi Zhuang, and 40.95, 45.91 and 13.14% in Han (P < 0.001); respectively. Serum high-density lipoprotein cholesterol (HDL-C) and apolipoprotein B levels in both ethnic groups were higher in LIPC -514T carriers than in C carriers. In addition, serum triglyceride levels in Han were higher in TT genotype individuals than in CC genotype subjects (P < 0.05). Serum HDL-C levels were positively correlated with age, alcohol consumption and LIPC -514C/T genotypes, and negatively associated with hypertension and cigarette smoking in Hei Yi Zhuang (P < 0.05-0.01), whereas HDL-C levels were positively correlated with age, alcohol consumption and LIPC -514C/T genotypes, and negatively associated with body mass index and cigarette smoking in Han (P < 0.05-0.001). The differences in serum HDL-C levels between the two ethnic groups might partially attribute to the differences in the LIPC -514C/T polymorphism.     

Vaccenic acid (<Emphasis Type="Italic">t</Emphasis>11–18∶1) is converted to <Emphasis Type="Italic">c</Emphasis>9,<Emphasis Type="Italic">t</Emphasis>11-CLA in MCF-7 and SW480 cancer cells

The aims of this study were to determine whether vaccenic acid (VA; t11–18∶1) is converted to c9,t11-CLA in human mammary (MCF-7) and colon (SW480) cancer cell lines and whether VA influences cell viability and other CLA-bioresponsive markers. When cells were incubated in the presence of VA at concentrations of 5 to 20 μg/mL, both VA and c9,t11-CLA increased in cellular lipids in a dose-dependent manner. After 4 d of incubation of SW480 and MCF-7 cells with VA (20 μg/mL), c9,t11-CLA increased from undetectable levels to 8.57 and 12.14 g/100 g FAME in cellular lipids, respectively. VA supplementation for 4 d at 5, 10, and 15 μg/mL had no effect on cell growth, whereas 20 μg/mL significantly (P<0.05) reduced cell growth in both cell lines. VA (20 μg/mL) treatment induced DNA fragmentation and significantly (P<0.05) depeleted cytosolic GSH levels in the SW480 cell line after 4 d of incubation, suggesting that apoptosis was the mode of cell death induced by VA. Both VA and c9,t11-CLA reduced (P<0.05) total ras expression in SW480 cells. ¹⁴C-Arachidonic acid uptake into the MG fraction was significantly increased (P<0.05) in both cell lines while uptake into the phospholipid fraction decreased in response to VA. VA treatment significantly (P<0.05) increased 8-epi-prostaglandin F_2α in both cell lines. The data indicate that growth suppression and cellular responses of both cells lines are likely mediated by VA desaturation to c9,t11-CLA via Δ⁹-desaturase.     

Properties of perovskite-like phases <Emphasis Type="Italic">Ln</Emphasis>BaCuFeO<Subscript>5 + δ</Subscript> (<Emphasis Type="Italic">Ln</Emphasis> = La,Pr)

The influence of the oxygen content on the crystal chemical parameters of the LnBaCuFeO_{5 + δ} (Ln = La, Pr) ferrocuprates is investigated using X-ray powder diffraction and IR spectroscopy. The electrical conductivity of these phases is studied. The chemical expansion coefficients α_δ and the activation energies E _a for electrical conduction are calculated. It is demonstrated that, for the LnBaCuFeO_{5 + δ} (Ln = La, Pr) phases, the chemical expansion coefficients ad depend on both the ionic radius of Ln ³⁺ cations and the oxygen nonstoichiometry of the ferrocuprate, whereas the activation energies E _a for electrical conduction are predominantly determined by the oxygen content in the samples.     

Solid Solution (AlN)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>(SiC)<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> ≈ 0.7) by SHS under High Pressure of Nitrogen Gas

Solid solution (AlN) _x (SiC)_1–x (x = 0.7) was prepared from Al–SiC mixtures by SHS under high pressure of nitrogen gas (50, 70 MPa) and characterized by XRD and SEM. Combustion product was found to have a wurtzite 2H structure with lattice parameters a = 3.10889 ± 0.00022 Å and c = 5.00741 ± 0.00080 Å.     

Direct-hydrothermal synthesis of LiFe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> cathode materials

Carbon free LiFe_1−x Mn _x PO₄ (x = 0, 0.05, 0.1, 0.2, 0.4) cathode materials were prepared by a direct-hydrothermal process at 170 °C for 10 h. The structural and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), charge–discharge experiments, cyclic voltammetry (CV) and alternating current (AC) impedance spectroscopy. The electrochemical performance of LiFePO₄ prepared in this manner showed to be positively affected by Mn²⁺-substitution. Among the Mn²⁺-substitution samples, the LiFe_0.9Mn_0.1PO₄ exhibited an initial discharge capacity of 141.4 mA h g⁻¹ at 0.1 C, and the capacity fading is only 2.7% after 50 cycles.     

Spatial localization of holes in La<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>CuO<Subscript>4</Subscript>

The parameters of the tensor of the electric field gradient (EFG) in cation sites of the La_{2 ? x} Sr _x CuO₄ lattice have been determined by the method of emission Mössbauer spectroscopy on ⁵⁷Co(^57m Fe), ⁶⁷Cu(⁶⁷Zn), ⁶⁷Ga(⁶⁷Zn), and ¹⁵⁵Eu(¹⁵⁵Gd) isotopes. There is no quantitative agreement between the calculated (the pointcharge model) and experimental values of the main component of the tensor EFG V _zz , which is explained by the absence of the reliable data on the Sternheimer coefficients for Fe³⁺, Zn²⁺, and Gd³⁺ ions. Based on the comparison of the calculated and experimental dependences of V _zz on x it was shown that the holes appearing during the substitution of La³⁺ for Sr²⁺ are localized preferably on the oxygen atoms that are in the same plane as the copper atoms, which is in agreement with the model discussed in the literature and assumes that the mechanism responsible for the high-temperature superconductivity of solid solutions La_{2 ? x} Sr _x CuO₄ is the interaction between the conductivity electrons and two-atomic two-electron centers with negative correlation energy.     

Fed-batch optimization of recombinant <Emphasis Type="Italic">α</Emphasis>-amylase production by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> using a modified Markov chain Monte Carlo technique

A modified Markov Chain Monte Carlo (MCMC) searching procedure was developed to search for an optimal set of decision variables and optimal feed rate trajectories for recombinant α-amylase expression by Bacillus subtilis ATCC 6051a. The bacterium also synthesizes proteases as undesirable products in fed-batch culture that need to be minimized. To maximize α-amylase productivity, a 14th-order fed-batch model was optimized by integrating Pontryagin’s maximum principle with the Luedeking-Piret equation. The number of iterations and simulations of the proposed searching procedure were statistically examined for accuracy and acceptability of the results. It can be concluded that the proposed searching procedure increased the parameter selection opportunity near the tail ends of redefined triangular distribution. By applying a modified MCMC searching procedure with 1,500 iterations, the predicted α-amylase productivity was improved by 18% in comparison with near-optimum experimental results. This productivity was 3.5% higher than predicted by conventional MCMC optimization.     

Distribution of nonequilibrium carriers in the region of a <Emphasis Type="Italic">p</Emphasis>–<Emphasis Type="Italic">n</Emphasis> junction under various photogeneration conditions

A model is described, which makes it possible to calculate the distribution of nonequilibrium carriers and an electric field near the p–n junction, which arose as a result of the internal photoeffect. Using laser illumination, the possibilities to control the properties of nanolayered structures sensitive to the concentration of free carriers are analyzed. The mutual location of the region of the intense absorption of radiation and the p–n junction itself is varied and the linear and square mechanisms of carrier recombination are analyzed.     

Rh<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Pd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Nanoparticle Composition Dependence in CO Oxidation by NO

Abstract  

Bimetallic 15 nm Pd-core Rh-shell Rh_1−x Pd _x nanoparticle catalysts have been synthesized and studied in CO oxidation by NO. The catalysts exhibited composition-dependent activity enhancement (synergy) in CO oxidation in high NO pressures. The observed synergetic effect is attributed to the favorable adsorption of CO on Pd in NO-rich conditions. The Pd-rich bimetallic catalysts deactivated after many hours of oxidation of CO by NO. After catalyst deactivation, product formation was proportional to the Rh molar fraction within the bimetallic nanoparticles. The deactivated catalysts were regenerated by heating the sample in UHV. This regeneration suggests that the deactivation was caused by the adsorption of nitrogen atoms on Pd sites.