Synthesis and Properties of Alkyl <Emphasis Type="Italic">β</Emphasis>-<Emphasis Type="SmallCaps">d</Emphasis>-Galactopyranoside

A series of alkyl β-d-galactopyranosides were prepared by the trichloroacetimidate method with d-galactose and alcohols with different chain lengths as raw materials. Their solubility, surface tension, emulsification, foaming, wettability, thermotropic liquid crystalline properties, and thermal stability were investigated. Alkyl β-d-galactopyranosides are soluble in water and ethanol, and the solubility decreases with increasing alkyl chain length. Decyl β-d-galactopyranoside was insoluble in water, but soluble in ethanol. Dissolution of alkyl β-d-galactopyranoside in water is an endothermic process with dissolution enthalpies greater than zero. Nonyl β-d-galactopyranoside had an excellent emulsifying property, better foaming ability and the best foam stability. The CMC values of alkyl β-d-galactopyranosides decrease with increasing of alkyl chain length. Alkyl β-d-galactopyranosides are thermally stable up to 270 °C. Alkyl β-d-galactopyranosides show the distinctive optical texture of a thermotropic liquid crystal smectic A type phase. Decyl β-d-galactopyranoside showed the strongest wettability.     

Synthesis and self-assembly of pH-responsive amphiphilic poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone)-<Emphasis Type="Italic">block</Emphasis>-poly(acrylic acid) copolymer

The pH-responsive amphiphilic poly(ε-caprolactone)-block-poly(acrylic acid) (PCL-b-PAA) copolymer was prepared by selective hydrolysis of one novel poly(ε-caprolactone)-block-poly(methoxymethyl acrylate) (PCL-b-PMOMA) block copolymer, which was synthesized by combining ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) and atom transfer radical polymerization (ATRP) of methoxymethyl acrylate (MOMA). Selective hydrolysis of the hemiketal ester groups on the PMOMA block gave 100% deprotection without the cleavage of the PCL block. The self-assembly behavior of PCL-b-PAA was investigated by fluorescence spectroscopy, DLS and TEM. The spherical micelles were formed with the hydrophobic PCL block as the core and the hydrophilic PAA as the shell by a co-solvent evaporation method. Moreover, the size and size distribution of the micelles varied with pH value and ionic strength in aqueous solution. The cytotoxicity of the PCL-b-PAA was lower, which was confirmed by MTT assay.     

Synthesis of novel polymer brushes of poly(acrylonitrile-<Emphasis Type="Italic">g</Emphasis>-<Emphasis Type="Italic">N,N</Emphasis>ʹ-dimethylaminoethyl methacrylate) by nitrile modification

Functional polymer brushes of poly(acrylonitrile-g-N,N?-dimethylaminoethyl methacrylate) were efficiently synthesized by a novel approach of combining Cu(0)-mediated controlled/“living” radical polymerization and nitrile click chemistry. The poly(acrylonitrile-g-N,N?-dimethylaminoethyl methacrylate) as a promising material exhibited excellent hydrophile–lipohile balance in the process of self-assembly and could autonomously develop the orderly structure micelle in N,N?-dimethylformamide/water mixture solvent for the potential application of a new drug delivery carrier. In the process of self-assembly, polyacrylonitrile acted as a backbone of the functional polymer brushes due to its hydrophobic feature and poly(N,N?-dimethylaminoethyl methacrylate) as the branch of functional polymer brushes due to its hydrophilic characteristic, which both were prepared by Cu(0)-mediated controlled/“living” radical polymerization with ethyl-bromoisobutyrate as initiator. Poly(N,N?-dimethylaminoethyl methacrylate) containing azide end group was synthesized by substitution reaction of poly(N,N?-dimethylaminoethyl methacrylate) containing bromine end groups with sodium azide in N,N?-dimethylformamide. The click reaction between the nitrile of polyacrylonitrile and the azide group of poly(N,N?-dimethylaminoethyl methacrylate) was carried out under ammonium chloride as catalyst in N,N?-dimethylformamide. The polymer was further confirmed by GPC, FTIR, ¹H NMR and TGA. Meanwhile, the micelles with different morphologies were observed by TEM, and the particle diameter distribution of self-assembled micelle from the PAN-g-PDMAEMA brushes was determined by DLS.     

Control of assembly size of poly (methacrylic acid)-<Emphasis Type=Italic>grafted</Emphasis> fullerenes in aqueous solution

We synthesized poly(methacrylic acid)-grafted fullerenes (PMA-C₆₀) with different PMA molecular weights and investigated the assembly size formed by PMA-C₆₀ in aqueous solution. The molecular weight of PMA strongly affects the assembly size: PMA-C₆₀ with a larger molecular weight forms micelles with 20 nm diameters while PMA-C₆₀ with a smaller molecular weight forms monodisperse assemblies with 200 nm hydrodynamic diameters. We succeeded in converting the large monodisperse assembly into micelles by adding either ionic species or ethanol. This result provides insight into controlling the assembly size of fullerene-containing assemblies.     

Recycling of legume residues for nitrogen economy and higher productivity in maize (<Emphasis Type="Italic">Zea mays</Emphasis>)–wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) cropping system

Contribution of legumes towards N economy in cereal-based cropping systems is well-known but there has been a gradual decline in the cultivation of grain legumes, threatening sustainability of maize (Zea mays)–wheat (Triticum aestivum) cropping system in north-western India. A study was made to evaluate and quantify the effect of different grain legumes on productivity, profitability, N economy and soil fertility in maize–wheat cropping system at New Delhi during 2002–2004. Five legumes, viz. blackgram (Vigna mungo), greengram (Vigna radiata), cowpea (Vigna unguiculata), groundnut (Arachis hypogaea) and soybean (Glycine max) were either intercropped with maize or grown in sole cropping, and their residues were incorporated before the following crop of wheat, which was grown with varying rates of N, viz. 0, 40, 80 and 120 kg N ha⁻¹. Maize-equivalent productivity was significantly more with intercropped greengram (16.1–29.9%), cowpea (24.8%) and groundnut (11.1–16.6%) than in sole maize. Land equivalent ratio and other competitive functions were favourably influenced with intercropped maize + greengram and maize + cowpea. Addition of N through legume residues varied from 11.5–38.5 kg ha⁻¹ in intercropped system and 17.5–83.5 kg ha⁻¹ in sole cropping, which improved productivity of following wheat to a variable extent. Nitrogen economy in wheat was 21 kg ha⁻¹ due to residue incorporation of intercropped greengram, cowpea and groundnut; and 49–56 kg N ha⁻¹ of sole cropped greengram and groundnut. Residual soil fertility in terms of organic C and KMnO₄-N showed an improvement under maize-based intercropping systems followed by wheat, and the beneficial effect was more pronounced with sole cropping of legumes due to greater addition of residues. Apparent N balance as well as actual change in KMnO₄-N at the end of study was positive in most intercropped legumes as well as sole cropping systems, with greater improvement noticed under groundnut, soybean and greengram. Net returns were marginal with maize-based intercropping or sole cropping of legumes, but improved considerably with wheat, particularly when greengram, cowpea and groundnut were grown in the previous season. The studies suggested that inclusion of grain legumes, particularly greengram, cowpea and groundnut was beneficial for improving productivity, profitability, N economy and soil fertility in maize–wheat cropping system.     

Regiospecific Analyses of Triacylglycerols of Hoki (<Emphasis Type="Italic">Macruronus novaezelandiae</Emphasis>) and Greenshell™ Mussel (<Emphasis Type="Italic">Perna canaliculus</Emphasis>)

The lipid profiles of the two most important New Zealand marine oil sources were investigated, with particular attention to the regioisomeric compositions of triacylglycerides (TAG), using ¹³C-nuclear magnetic resonance analysis. Oils from hoki (Macruronus novaezelandiae) and Greenshell™ mussel (Perna canaliculus) (GSM) were analyzed for their lipid content, lipid class and fatty acid profile. The regiospecific distribution of long chain (C ≥ 20) polyunsaturated fatty acids (LC-PUFA) between the sn-1,3 and sn-2 glycerol positions was calculated from ¹³C responses in the carbonyl region in the triacylglycerol fraction. Rendered hoki oil (RHO) produced from the viscera and filleting discards, had a similar lipid profile to that of hoki liver oil (HLO) confirming that the liver is the major source of oil in RHO. The regioisomeric distribution of fatty acids showed differences between the two oil sources. Docosahexaenoic acid (DHA) had a regioisomeric distributional preference to the sn-2 position in TAG from all the oils (59.2% HLO, 54.3% RHO and 63.4% GSM). Eicosapentaenoic acid (EPA) had a more even distribution along the triacylglycerol backbone in hoki TAG (29.1% HLO, 33.6% RHO) while there was a slight sn-2 positional preference in the GSM TAG (37.6%). This regioisomeric information is vital to distinguish LC-PUFA-rich marine oils from other marine sources for authentication purposes.     

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.     

Oxygen nonstoichiometry of layered oxides <Emphasis Type=Italic>Ln</Emphasis>BaCuFeO<Subscript>5 + δ</Subscript> (<Emphasis Type=Italic>Ln</Emphasis> = La,Pr)

The oxygen exchange between powders of the layered oxides LnBaCuFeO_{5 + δ} (Ln = La, Pr) and the environment and the oxygen nonstoichiometry index δ of these oxides have been investigated using solidelectrolyte coulometry in the temperature range 20–800°C and at oxygen partial pressures in the range 3–346 Pa. It has been found that the evolution (absorption) of oxygen by the powdered samples proceeds in two stages and that the transition between the stages corresponds to a particular value of the degree of filling of the layers with oxygen (δ ≈ 0.25 for Ln = La and δ ≈ 0.125 for Ln = Pr). The conclusion has been drawn from analyzing the results obtained that, in the layers -LnO_δ-of the crystal structure of the LnBaCuFeO_{5 + δ} phases, oxygen undergoes a sequential ordering and that, in these layers, oxygen can exist in two forms: ordered and disordered. The latter form represents weakly bound oxygen which can be easily exchanged between the samples and the environment.     

Living Anionic Polymerization of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>–Dimethylacrylamide and Copolymerization with Methyl Methacrylate in the presence of Bulky Aluminum Phenoxide

Summary Anionic polymerization of N,N–dimethylacrylamide (DMAAm) was examined in toluene with tert–butyllithium (t–BuLi)/bis(2,6–di–tert–butylphenoxy)ethylaluminum [EtA1(ODBP)₂]. In the presence of excess amounts of the aluminum compound over t–BuLi, the polymerization proceeded in a living manner. Sequential block copolymerization of DMAAm and methyl methacrylate (MMA) with the same initiator underwent smoothly in both directions, that is, polymerization of MMA by poly(DMAAm) living anions and vice versa. Moreover, the copolymerization of an equimolar mixture of DMAAm and MMA proceeded in a monomer–selective manner to give a block–like copolymer; DMAAm was polymerized first followed by MMA polymerization through selective activation of DMAAm by the coordination of EtA1(ODBP)₂.     

pH- and thermo-sensitive semi-IPN hydrogels composed of chitosan, <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide,and poly(ethylene glycol)-<Emphasis Type="Italic">co</Emphasis>-poly(ε-caprolactone) macromer for drug delivery

In this study, semi-IPN chitosan/poly(N-isopropylacrylamide) (PNIPAAm) hydrogels have been prepared via in situ UV-photo-crosslinking of N-isopropylacrylamide monomer using poly(ethylene glycol)-co-poly(ε-caprolactone) (PEG-co-PCL) macromer as a crosslinker in the presence of chitosan. Swelling properties of the resultant hydrogels were studied by investigating pH- and temperature dependence of equilibrium swelling ratio and oscillatory swelling–deswelling kinetics. It was found that semi-IPN hydrogels responded to both temperature and pH changes, and such stimuli-responsiveness was rapidly reversible. The rheological measurements demonstrated that the incorporation of chitosan greatly improved the mechanical strength of the hydrogels prepared. The release profiles of bovine serum albumin (BSA) from the hydrogels were also evaluated. The results showed that the release rate of BSA was higher in pH 2.0 buffer solution than in pH 7.4 buffer solution at 37 °C. Such double-sensitive hydrogels have the potential to use as smart carriers for drug delivery systems.     

Improvement of passivity of Fe–<Emphasis Type=Italic>x</Emphasis>Cr Alloys (<Emphasis Type=Italic>x</Emphasis> < 10%) by cycling through the reactivation potential

Classically, 13% Cr is required for stable passivity of a Fe–Cr alloy in acidic and neutral solutions not containing inhibitors. Some authors (Mansfeld, Fujimoto) have published potential cycling procedures that generate thick Cr-rich films. In this work, a similar technique, but with a far smaller potential cycle, was used to enrich a surface layer in chromium, thereby increasing corrosion-resistance in otherwise non-passivating steels. This was achieved by potential stepping across the iron reactivation potential, firstly forming passive iron(III) oxide, then reducing it to soluble iron(II) ions, while ensuring the passivity of chromium. The use of potential stepping was found to result in a more robust film than that formed through a single continuous passivation step.     

On the Chemical Origin of the Gap Bowing in (GaAs)<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript>Ge<Subscript>2<Emphasis Type=Italic>x</Emphasis></Subscript> Alloys: A Combined DFT–QS<Emphasis Type=Italic>GW</Emphasis> Study

Motivated by the research and analysis of new materials for photovoltaics and by the possibility of tailoring their optical properties for improved solar energy conversion, we have focused our attention on the (GaAs)_{1− x} Ge_2x series of alloys. We have investigated the structural properties of some (GaAs)_{1− x} Ge_2x compounds within the local-density approximation to density-functional theory, and their optical properties within the Quasiparticle Self-consistent GW approximation. The QSGW results confirm the experimental evidence of asymmetric bandgap bowing. It is explained in terms of violations of the octet rule, as well as in terms of the order–disorder phase transition.     

(±)-Catechin,A Root Exudate of the Invasive <Emphasis Type="Italic">Centaurea Stoebe</Emphasis> Lam. (Spotted Knapweed) Exhibits Bacteriostatic Activity Against Multiple Soil Bacterial Populations

Understanding the effects of allelopathic plant chemicals on soil microorganisms is critical to understanding their ecological roles and importance in exotic plant invasion. Centaurea stoebe Lam. (spotted knapweed), an aggressive invasive weed in North America, secretes a racemic mixture of (±)-catechin as a root exudate. This enantiomeric, polyphenolic compound has been reported to have allelopathic effects on surrounding flora and microflora. To better understand how catechin affects microbial communities in the root zone of spotted knapweed, we assessed its impact on the total culturable bacterial component and numerous individual bacterial populations from Romanian (native range) and Montana (invaded range) soils. Catechin suppressed total culturable count numbers from the bacterial community and inhibited growth of some, but not all, soil bacterial populations tested. The native soil bacterial community was significantly more resistant to inhibitory effects of catechin than either the invaded or non-invaded soils. We further show that the inhibitory effect of catechin on nine different soil bacterial strains from seven genera was reversible, demonstrating that it acts via a bacteriostatic rather than bactericidal mechanism. These findings suggest that catechin might affect bacterial community composition and activity in the root zone.     

Kinetics of stepwise bulk crystallization of AsSe<Subscript>1.5</Subscript>Sn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> ≤ 0.28) glasses

The kinetics of stepwise transformations during bulk isothermal crystallization of semiconducting AsSe_1.5Sn _x (x = 0.13, 0.20, 0.28) glasses has been studied in the temperature range of 210?310°С using ¹¹⁹Sn Mössbauer spectroscopy, XPA, and the density and microhardness measurements of the quenched specimens. The kinetics of the gross bulk crystallization of glasses have been analyzed according to the data on density measurement using the Kolmogorov–Avrami equation, which was generalized on stepwise and incomplete isothermal transformations.     

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.     

A Kinetics and Mechanism Investigation of the Nucleophilic Substitution Reaction of <Emphasis Type=Italic>α-</Emphasis>Chlorododecyl Carboxylate with Trimethylamine

A nucleophilic substitution reaction was developed to synthesize the zwitterionic surfactant using a renewable natural fatty acid rather than a petroleum derivative as the raw material. The kinetics and mechanism of the nucleophilic substitution reaction of trimethylamine α-chlorododecyl carboxylate with trimethylamine were investigated in protic and dipolar aprotic solvents including water, ethanol and N, N-dimethyl formamide. The rate equations were derived using initial rates and the activation parameters in different solvents were determined empirically and compared with each other to obtain important information about the reaction mechanism. The overall second-order reaction number and the negative activation entropy supported a bimolecular nucleophilic substitution (S_N2) mechanism, combined with the pseudo-first-order kinetics for each reactant. The experimental results also showed that the reaction reactivity diminishes with the decrease in polarity of protic solvents. The typical dipolar aprotic solvent dimethyl formamide distinctively promoted the reaction in. This fact was successfully explained by the solvation rule for S_N2 reactions.     

Synthesis,characterization and acidochromism of Poly (2-<Emphasis Type="Italic">N,N</Emphasis>–dimethylamino-4,6-Bis (2-thienyl)-pyrimidine)

A new monomer (2-N,N-dimethylamino-4,6-Bis (2-thienyl)–pyrimidine) was synthesized and its homopolymer was successfully prepared by using Ferric trichloride (FeCl₃) as an oxidant. The structure of the polymer and monomer was fully characterized by ¹H–NMR, FTIR, UV-vis, Fluorescent spectroscopy and X-ray diffraction pattern. The polymer gives rise to a band at λ _max = 391 nm. The polymer showed the PL spectrum, gave a peak at 507 nm.We have observed that the polymer was sensitive to inorganic acids and the acidochromism behavior was investigated applying organic acid such as CF₃COOH. The corresponding UV-Vis peaks were observed at 464 nm and 357 nm respectively. X-ray diffraction data shows that polymer has a certain crystallinity. The polymer exhibited an [η] value of 0.26 dLg⁻¹ at 25 °C in H₂SO₄ (w = 98%).     

Sol-Gel Synthesis,Thermal Behavior of Nanopowders and Chemical Stability of La<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript>Ho<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript> Ceramic Matrices

Nanosized powders of orthophosphates in the LaPO₄–HoPO₄–H₂O system have been synthesized to determine the mutual solubility of LaPO₄ · nH₂O and HoPO₄ · nH₂O initial components and to obtain ceramic matrices by sintering them. Formation of hexagonal, monoclinic or tetragonal solid solutions was revealed, and their limits and thermal stability were determined. A series of limited hexagonal LaPO₄ · nH₂O-based solid solutions was observed within the 0 ≤ x ≤ 0.6 concentration range up to 600°C. Further they transformed to monoclinic LaPO₄-based form within the 0 ≤ x ≤ 0.3 concentration range. Solubility of LaPO₄ · nH₂O and LaPO₄ in tetragonal HoPO₄(· nH₂O) is lower (≤10 mol %). Specific surface area of La_1–xHo_xPO₄ · nH₂O powders was in the range of 90.5–165.0 m²/g depending on x. Leaching rate of La³⁺ and Ho³⁺ from La_1–xHo_xPO₄ matrices in nitric acid solution (pH 1–2) was determined to be 10^–5–10^–2 g/(cm² day) for both ions.     

One-Pot Preparation of <Emphasis Type="SmallCaps">d</Emphasis>-Amino Acids Through Biocatalytic Deracemization Using Alanine Dehydrogenase and ω-Transaminase

d-Amino acids are pharmaceutically important building blocks, leading to a great deal of research efforts to develop cost-effective synthetic methods. Preparation of d-amino acids by deracemization has been conceptually attractive owing to facile synthesis of racemic amino acids by Strecker synthesis. Here, we demonstrated biocatalytic deracemization of aliphatic amino acids into d-enantiomers by running cascade reactions; (1) stereoinversion of l-amino acid to a d-form by amino acid dehydrogenase and ω-transaminase and (2) regeneration of NAD⁺ by NADH oxidase. Under the cascade reaction conditions containing 100 mM isopropylamine and 1 mM NAD⁺, complete deracemization of 100 mM dl-alanine was achieved after 24 h with 95% reaction yield of d-alanine (>?99% ee^D, 52% isolation yield).

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