Reducibility of Ce 1-x Zr x O 2: Origin of Enhanced Oxygen Storage Capacity

We combine first-principles calculations with EXAFS studies to investigate the origin of high oxygen storage capacity in ceria-zirconia solid solution, prepared by solution combustion method. We find that nanocrystalline Ce_0.5Zr_0.5O₂ can be reduced to Ce_0.5Zr_0.5O_1.57 by H₂ upto 850 °C with an OSC of 65 cc/gm which is extremely high. Calculated local atomic-scale structure reveals the presence of long and short bonds resulting in four-fold coordination of the cations, confirmed by the EXAFS studies. Bond valence analysis of the microscopic structure and energetics is used to evaluate the strength of binding of different oxide ions and vacancies. We find the presence of strongly and weakly bound oxygens, of which the latter are responsible for the higher oxygen storage capacity in the mixed oxides than in the pure CeO₂.     

Environmentally friendly natural polyhydroxylic compounds in electroless copper plating baths: application of xylitol, <Emphasis Type="SmallCaps">D</Emphasis>-mannitol and <Emphasis Type="SmallCaps">D</Emphasis>-sorbitol as copper(II) ligands

The possibility of using xylitol, D-mannitol and D-sorbitol as Cu(II) ligands in electroless copper baths was demonstrated. The ligands mentioned showed good chelating properties for Cu(II) ions in alkaline media (pH > 11.5), i.e. under conditions of the use of traditional formaldehyde-containing solutions. Electroless copper plating solutions containing the chelators xylitol, D-mannitol and D-sorbitol are stable and, under the optimal conditions selected, copper coatings up to 3 m thick can be obtained in 1 h at ambient temperatures.     

Sex Pheromone of the Scarab Beetle <Emphasis Type="Italic">Phyllophaga</Emphasis> (<Emphasis Type="Italic">Phytalus) georgiana</Emphasis> (Horn)

The sex pheromone of Phyllophaga (Phytalus) georgiana was characterized as valine methyl ester, tentatively the l-enantiomer. This is the first sex pheromone identified from the Phyllophaga subgenus Phytalus. The pheromone was extracted from female glands, the active component isolated by coupled gas chromatography–electroantennogram detection analysis, characterized by mass spectrometry, and shown to be active in field tests. The seasonal flight pattern was determined for P. georgiana as well as for three other species, P. anxia (both northern and southern genitalic forms), P. gracilis, and P. postrema. The latter three species were captured in traps baited with l-isoleucine methyl ester. Sridhar Polavarapu, deceased May 7, 2004. We dedicate this publication to our friend and colleague.     

Another new family of “extended” glucidoamphiphiles. Synthesis and surfactant properties for different sugar head groups and spacer arm lengths

Following a new four-step route, we prepared a family of “extended” glucidoamphiphiles from D-glucose, D-galactose, and xylitol in which the n-dodecyl chain is attached to the glucidic moiety by the linkage Z=O-Et-O-Et-O-(α-PP-O-) _n′ where-O-(α-PP-O-) _n is a poly-(α-propyloxy) commercial oligomeric mixture (with average length n=6, 10, and 14). This amphiphilic behavior study showed that (i) the glucose derivative exhibits water solubility and hydrophilic-lipophilic balance values that are close to those found for the glucose compound with Z=-O-(α-PP-O-) _n (without the Et-O-Et group), (ii) all these compounds are more strongly hydrophilic than the corresponding glucidic derivatives with Z=O, (iii) the increase of the poly-(α-propyloxy) chain length from ñ=6 to ñ=14 tends to reduce the hydrophilicity slightly.     

Direct <Emphasis Type="SmallCaps">d</Emphasis>-Glucose Oxidation over Noble Metal Nanoparticles Introduced on Polymer and Inorganic Supports

In the present work, nanocatalysts prepared on inorganic supports (zeolites) were investigated in d-glucose oxidation and compared to systems supported on polymer (hypercrosslinked polystyrene (HPS)) previously described. Catalytic activities and selectivities were measured under various reaction conditions. The selectivity of d-glucose oxidation and activity of both Pd-containing zeolites and HPS-Ru were similar (99.7% and TOF 0.013–0.014 mol/(mol Me s)). Physicochemical analysis X-ray photoelectron spectroscopy, liquid nitrogen physisorption, diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO for metal sites evaluation, CD₃CN for acid sites evaluation showed that Pd species were in oxidic form, while Ru species were in oxidic and reduced form. The catalytic activity decreased when acidic sites were present in Pd-containing zeolites.     

An Interesting Complex: [Cd(l -trp) (d-trp)] n

A novel coordination polymer [Cd(l-trp) (d-trp)] _n (where l-trp and d-trp are l-tryptophan and d-tryptophan or (S)-2-amino-3-(3-indolyl)propionic acid and (R)-2-amino-3-(3-indolyl)propionic acid) was prepared by a solvent-thermal method and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The compound(monoclinic space group P2(1)/c with a = 19.759(2) Å, b = 5.2496(10) Å, c = 9.7594(16) Å, β = 97.2760(10)°, Z = 2) shows a two-dimensional plane structure. The crystallized coordination polymer has a centrosymmetric space group. Each Cd²⁺ ion coordinates with a pair of racemes, and the complex is a mesomer. Although l-trp was used, both l-trp and d-trp appear in the complex.     

Experimental Evidence for Three Pheromone Races of the Scarab Beetle <Emphasis Type="Italic">Phyllophaga anxia</Emphasis> (LeConte)

This study offers experimental evidence for the existence of three pheromone races of the northern genitalic form of Phyllophaga anxia: one race in which females produce and males respond mainly to l-valine methyl ester, a second producing and responding to l-isoleucine methyl ester, and a third producing and responding to an intermediate range of blends of the two compounds. At Franklinville, NY, pheromone gland contents of females were analyzed using coupled gas chromatography–electroantennogram detection. Two types of females were found, one that produced greater than 99% l-valine methyl ester and another that produced greater than 99% l-isoleucine methyl ester. Capture–mark–release–recapture field tests with males at Franklinville established that most males were recaptured in traps baited with the same blends with which they were originally captured. The populations characterized at Franklinville, NY, have also been found at numerous locations from eastern Canada and the northeast and north central USA, sometimes in allopatry and sometimes in sympatry. At a site in Carver, MA, P. anxia males responded to blends of the methyl esters of l-valine and l-isoleucine, and Carver females produced blends similar to those to which the males responded. Populations responding to blends have been identified only from southeastern Massachusetts and Rhode Island. At a field site near Waterloo, NY, the addition of small proportions of l-isoleucine methyl ester to lures containing l-valine methyl ester did not affect trap captures, but higher proportions of l-isoleucine methyl ester were inhibitory, decreasing trap captures.     

Synthesis and surfactant properties of a new “extended” glucidoamphiphile made from D-glucose

We prepared a new nonionic surfactant, 8, in which the n-dodecyl chain is attached at the C-3 carbon of the D-glucose-based glucopyranose moiety by the linkage Z=?O-(α-PP-O) _n with ?O-(α-PP-O) _n being a commercial poly-(α-propyloxy) oligomeric mixture (with average ñ=6). This amphiphilic behavior study showed that, when compared to the reference compound 3-O-dodecyl-D-glucopyranose (Z=O), compound 8 exhibits (i) a water solubility that is 100-fold higher, (ii) a hydrophilic-lipophilic balance value increase from 8.5 to 12.6 units, and (iii) a slighly lower critical micelle concentration.     

Allelochemicals fromPolygonum sachalinense Fr. Schm. (Polygonaceae)

The root exudates fromPolygonum sachalinense in a recirculating system significantly inhibited lettuce seedling growth. The rhizomes and roots ofP. sachalinense were extracted with 80% acetone. Bioassay of the neutral-acidic fraction on the TLC agar plate showed the inhibitory activity corresponded to the two yellow pigment bands. Two orange needles were isolated and identified as anthraquinone compounds: emodin and physcion. Both compounds exhibited inhibitory activities against the seedling growth of several testing plant species. Glucosides were isolated fromP. sachalinense and were identified as emodin-1-O-β-D-glucoside and physcion-1-O-β-D-glucoside, respectively. On plant growth bioassay, these glucosides showed no phytotoxic activity against lettuce seedlings. The concentrations of emodin, physcion, and their glucosides from rhizome with roots, aerial parts, fallen leaves, and soil were determined. The rhizome with roots and fallen leaves contained emodin and physcion at relatively high concentrations. Emodin also occurs in the soil of this plant community with effective concentrations in the fall. The results indicate that these anthraquinones are responsible for the observed interference and are potent allelopathic substances.     

A homogeneous redox catalytic process for the paired synthesis of l-cysteine and l-cysteic acid from l-cystine

Redox catalytic process involved in the paired electrosynthesis of l-cysteine and l-cysteic acid from l-cystine is investigated by cyclic voltammetric technique and also confirmed by preparative electrolysis. The cyclic voltammetric behaviour shows that in the catholyte, in situ deposited tin (Sn) surface acts as a redox catalyst for the electro-reduction of l-cystine to l-cysteine whereas in the anolyte, the electro-generated bromine acts as a homogeneous redox mediator to enhance the electro-oxidation of l-cystine. l-Cysteine hydrochloride monohydrate (l-cysteine) and l-cysteic acid are prepared from l-cystine by preparative electrolysis with high purity and high yield using graphite cathode and DSA anode. At optimum concentration of l-cystine with 1:1 concentration ratio (catholyte:anolyte), the material yield obtained for l-cysteine is above 80% and that for l-cysteic acid is close to 60% in the paired electrosynthesis process in the batch operation. Scope for further experiments in conversion efficiency is also discussed.     

Continuous production of acyl <Emphasis Type="SmallCaps">l</Emphasis>-ascorbates using a packed-bed reactor with immobilized lipase

Saturated acyl (6-O-caproyl, lauroyl, and myristoyl) and unsaturated acyl (6-O-oleoyl, linoleoyl, and arachidonoyl) l-ascorbates were continuously synthesized at 50°C using a system where a column packed with ascorbic acid powder and a packed-bed reactor with an immobilized lipase from Candida antarctica were connected in series. A productivity of 1.6–1.9 kg/L reactor·d was achieved for at least 11 d. The surface tension of the caproyl or lauroyl l-ascorbate in aqueous solution was measured at various temperatures and pH to estimate the critical micelle concentration (CMC) of the acyl l-ascorbate. The CMC values were independent of temperature but dependent on the pH. The value of the caproyl ascorbate increased with an increase in pH.     

Synthesis, characterization and degradation of poly(dl-lactide)-block-polyvinylpyrrolidone-block-poly(dl-lactide) copolymers

A new kind of A-B-A block copolymers with good biocompatibility and adjustable degradability was synthesized by ring-opening polymerization, in which DL-lactide polymerized and grew from the two ends of polyvinylpyrrolidone (PVP). The well-defined triblock structures of copolymers were characterized by GPC, ¹H NMR, FTIR and DSC. There were two pronounced glass transition temperatures which showed apparent microphase separations between hydrophilic PVP segment and hydrophobic poly(dl-lactide) (PDLLA) segments. The hydrolytic degradation of PDLLA and copolymers in phosphate buffer solution (PBS, pH = 7.4) showed that the degradation rate of copolymers apparently became faster in comparison with that of PDLLA homopolymer, and increased with increasing PVP content. The measurements through ¹H NMR and FTIR showed that the degraded fragments contained PDLLA oligomers, lactates and soluble chains composed of PVP blocks attached with short PDLLA ones.     

Preparation and properties of new surfactants containingd-glucosamine as the building block

Three types of new surfactants were prepared by usingN-acetyl-d-glucosamine as a starting material. The first type of surfactant, sodium methyl 4,6-O-alkylidene-2-(carboxyl-atomethylamino)-2-deoxy-d-glucopyranoside, was prepared successively by the following treatments: methyl glucosidation ofN-acetyl-d-glucosamine, transacetalization with an appropriate aldehyde dimethyl acetal, deacetylation, and finally reaction of the resulting methyl-4,6-O-alkylidene-2-amino-2-deoxy-d-glucopyranoside (2-amino precursor) with bromoacetic acid. The reaction of this 2-amino precursor with methyl iodide yielded the second type of surfactant, methyl 4,6-O-alkylidene-2-deoxy-2-(trimethylammonio)-d-glucopyranoside iodide, in excellent yield. The last type of compound, sodium methyl 2-acetamide-4,6-O-alkylidene-3-O-[1-(carboxylato)-ethyl]-2-deoxy-d-glucopyranoside, was synthesized by the reaction of methyl 2-acetamide-4,6-O-alkylidene-2-deoxy-d-glucopyranoside with 2-chloropropionic acid. Concerning the two carboxylate types of surfactants, the compounds containing a C₉ or C₁₁ hydrophobic chain in the alkylidene part showed higher water solubility than the corresponding compounds containing a C₇ hydrophobic chain. Both the micelle-forming property and the ability to lower the surface tension of these carboxylate types of compounds increased with an increase in the length of the hydrophobic chain in the alkylidene part. These compounds can be applied to new acid-decomposable types of cleavable surfactants because they contain an acetal group. The acetal bond of the ammonium type of compound was cleaved more slowly than that of the corresponding carboxylate types of surfactants in 2% aqueous HCI solution. The biodegradabilities of these compounds were also determined.     

Lipase-catalyzed synthesis of unsaturated acyl l-ascorbates and their ability to suppress the autoxidation of polyunsaturated fatty acids

l-Ascorbic acid and various polyunsaturated fatty acids (PUFA) were condensed at 55°C by the immobilized lipase Chirazyme l-2 in dry acetone to produce the unsaturated acyl ascorbates. The PUFA moieties of the products were much more resistant to autoxidation at 65°C and nearly 0% relative humidity than the corresponding unmodified PUFA. The effects of the molar ratio of ascorbic acid or linoleoyl ascorbate to linoleic acid on the autoxidation of linoleic acid were examined. The autoxidation of linoleic acid was effectively suppressed at molar ratios greater than or equal to 0.2 when either ascorbic acid or linoleoyl ascorbate was mixed with linoleic acid. The addition of lauroyl ascorbate, synthesized through the enzyme-catalyzed condensation of ascorbic acid and lauric acid in acetone, to docosahexaenoic acid also significantly suppressed the autoxidation of docosahexaenoic acid at molar ratios of ≥0.2.     

Mechanism of Selective Phytotoxicity of l-3,4-Dihydroxyphenylalanine (l-Dopa) in Barnyardglass and Lettuce

l-3,4-Dihydroxyphenylalanine (l-dopa) is one of the few allelochemicals in which the phytotoxic action mechanism has been studied. Excess exogenous l-dopa suppresses root elongation in some plant species, and the inhibitory action is species-selective. The main factor of phytotoxicity of l-dopa is considered to be oxidative damage by reactive oxygen species (ROS) and/or free radical species (FRS). This study was performed to elucidate the mechanism of species-selective phytotoxicity. The involvement of ROS/FRS and polyphenol oxidase (PPO) in species-selective phytotoxicity was examined with barnyardgrass (Echinochloa crus-galli L.) and lettuce (Lactuca sativa L.), tolerant and susceptible species, respectively. Lipid peroxidation and melanin accumulation correlated with growth inhibition by L-dopa. Antioxidants, ascorbic acid and α-tocopherol, decreased lipid peroxidation and melanin accumulation and rescued lettuce root from growth inhibition. The oxidation of L-dopa by PPO was much greater in lettuce than in barnyardgrass. From these results, the phytotoxicity of L-dopa is considered due to the oxidative damage caused by ROS/FRS generated from the melanin synthesis pathway. PPO activity might be involved in the mechanism of species-selective phytotoxicity between barnyardgrass and lettuce.     

Ammonia utilization by the bruchid beetle,Caryedes brasiliensis [Bruchidae]

The seed predator,Caryedes brasiliensis [Bruchidae] generates appreciable ammonia in its dietary use and detoxification ofl-canavanine and its catabolic product,l-canaline.l-Canavanine is a toxic allelochemical ofDioclea megacarpa seeds, the food of the developing larvae. Bruchid beetle larvae rely upon glutamic acid dehydrogenase and glutamine synthetase to use ammonia for glutamic acid synthesis from 2-oxoglutaric acid and conversion of the former to glutamine. These reactions provide the larvae with a means for metabolically eliminating ammonia. Proline serves as a carbon skeleton source for glutamic acid formation.     

Self-Assembly of Metalloporphyrin-L-Cysteine Modified Gold Electrode

A novel composite film containing metalloporphyrins was fabricated by in situ electrochemical scanning on an L-cysteine self-assembled monolayer modified gold electrode. SEM and ATR-FTIR were used to characterize the structure of the film. The electrochemical properties were investigated through techniques such as a.c. impedance, cyclic voltammetry and chronocoulometry. The porphyrin-L-cysteine film showed no peak in the first cycle, while each of the composite films derived from three different metalloporphyrin-L-cysteines presented a pair of reversible redox peaks in 1.0 mol L^–1 H₂SO₄. These peaks correspond to the rapid redox process of the metal. The supporting electrolyte and its pH value influenced the stability and sensitivity of the composite film. Cupric-porphyrin-L-cysteine film showed good catalytic activity for the reduction of H₂O₂. The catalytic current was linear to H₂O₂ concentration in the range 1.0 × 10^–6 to 3.0 × 10^–5 mol L^–1, with a correlation coefficient of 0.9995. The detection limit was 1.0 × 10^–7 mol L^–1 at a signal to noise ratio of 3. The relative standard deviation was calculated as 2.4% for solutions containing 1.0 × 10^–5 mol L^–1 H₂O₂(n= 11).     

Asymmetric Aldol Reaction Catalyzed by New Recyclable Polystyrene-supported l-proline in the Presence of Water

Two l-proline-based linear polystyrene anchored catalysts (1a–b) have been efficiently synthesized. By using only 5 mol% of catalysts, the corresponding products of the aldol reaction were obtained in good yields (up to 91%) with excellent anti diastereoselectivity (up to 93:7) and enantioselectivity (up to 98% ee) in DMF in the presence of water. The yields of these reactions in the ketone/water mixture were lower than those in wet DMF (up to 84%). However, the stereoselectivity was comparable (up to 92:8 anti/syn ratio and 96% ee, respectively). In addition, catalysts 1a–b could be recovered by a simple precipitation and filtration process. They can also be re-used for at least five times without obvious loss of catalytic efficiency.     

Involvement of reactive oxygen species generated from melanin synthesis pathway in phytotoxicty of <Emphasis Type="SmallCaps">L</Emphasis>-Dopa

l-DOPA is an active allelochemical that inhibits plant growth. To determine whether the phytotoxicity is due to the reactive oxygen species generated during its oxidation to melanin, oxidative damage, melanin accumulation, and the effect of antioxidants on its phytotoxicity were examined in l-DOPA-tolerant (barnyard grass) and -susceptible (lettuce) plants, and in suspension-cultured carrot cells. l-DOPA suppressed root elongation in lettuce compared to barnyard grass. Levels of melanin and thiobarbituric acid reactive substances (TBARS) increased remarkably in l-DOPA-treated lettuce roots, but not in barnyard grass. l-DOPA also suppressed carrot cell growth to 60% of the control at 1 mM. Melanin content in 1 mM l-DOPA-treated carrot cells increased continuously; however, ascorbic acid and -tocopherol suppressed accumulation. When melanin formation was inhibited by ascorbic acid and -tocopherol, growth of l-DOPA-treated cells was restored. TBARS levels were higher in 1 mM l-DOPA-treated carrot cells than in untreated control cells 2 d after treatment, but not at 4 or 6 d. Ascorbic acid and -tocopherol suppressed the production of lipid peroxide during the initial 2 d. These results suggest that the phytotoxicity of l-DOPA is due to oxidative stress caused by reactive oxygen species from the melanin synthesis pathway.     

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.