Effects of fabrication conditions on the structure and function of membranes formed from poly(acrylonitrile–vinylchloride)

Phase-inversion membranes formed from poly(acrylonitril–co-vinylchloride) (PAN–PVC) have been utilized for encapsulating living cells for transplantation; however, a detailed analysis of the structure and function of the integral skin layer has not been reported. PAN–PVC membranes fabricated under different precipitation conditions were analyzed using microscopic techniques and several functional tests. Structural analysis with scanning atomic force microscopy (AFM) revealed the presence of nodular elements in the skin layer which changed as a function of precipitation conditions. In addition, membrane hydraulic permeabilities, sieving coefficients, and diffusive permeabilities also varied with precipitation conditions. Furthermore, changes in the functional properties could be related to the size of the nodular elements and their accompanying interstitial space. The results provide insight into the fundamental interrelationships that exist between membrane fabrication, the fine surface morphology of the skin layer, and membrane performance.     

Effects of crude and partially purified extracts from UV-B-irradiated rice leaves on Helicoverpa armigera (Hübner)

The effect of crude and partially purified extracts from ultraviolet-B (UV-B)-irradiated rice (Oryza sativa L.) leaves on the growth and development of corn earworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), was investigated. Fifty muL droplets of a liquid diet containing different concentrations of the crude and partially purified extracts were fed to H. armigera neonates to determine possible short-term toxicity effects. A choice test using a solid artificial diet was also performed to determine larval feeding preferences and antifeedant effects. To study effects on the life history of the insect, different concentrations of the crude and partially purified extracts were also incorporated in the artificial diet and fed to individually confined neonates of H. armigera. The neonates were reared up to the adult stage. Results showed that crude and partially purified extracts of UV-B-irradiated rice leaves demonstrated antifeedant, growth-inhibitory and antibiotic properties against H. armigera. At high concentrations, the extract initially stimulated larval feeding; however, there were subsequent negative effects on pupal and adult traits, thereby reducing the reproductive potential of adults. These partially purified extracts appeared to have an antifertility effect because adults laid fewer eggs and, of those eggs laid, viability was lower. These results suggest that the accumulated flavonoids or other phenolics in UV-B-irradiated leaves, extracted from UV-B-resistant rice cultivar 'M202,' affected the growth, development and reproduction of H. armigera, a polyphagous insect pest.     

Probing the Effects of Antimicrobial-Lysozyme Derivatization on Enzymatic Degradation of Poly(ε-caprolactone) Film and Fiber

Surface derivatization is essential for incorporating unique functionalities into biodegradable polymers. Nonetheless, its precise effects on enzymatic biodegradation still lack comprehensive understanding. In this study, a facile solution-based method is employed to surface derivatize poly(ε-caprolactone) films and electrospun fibers with lysozyme, aiming to impart antimicrobial properties and examine the impact on enzymatic degradation. The derivatized films and fibers have shown high antibacterial efficacy against Escherichia coli and Staphylococcus aureus. Through gravimetric analysis, it is observed that the degradation rate experiences a slight decrease upon lysozyme derivatization. However, this reduction is effectively countered by the inclusion of Tween-20, as affirmed by isothermal titration calorimetry. Comparing films and fibers, the latter undergoes degradation at a more accelerated pace, coupled with a rapid decline in molecular weight. This study provides valuable insights into the factors influencing the degradation of surface-derivatized biopolymers through electrospinning, offering a simple strategy to mitigate biomaterial-associated infections.     

Electrochemical Co-reduction of Bi(Ⅲ)and Y(Ⅲ)and Extracting Yttrium from Molten LiCl-KCl Using Liquid Bi as Cathode

The electrochemical reaction of Bi(Ⅲ)and co-reduction behaviour of Bi(Ⅲ)and Y(Ⅲ)ions were researched in molten LiCl-KCl on a ttmgsten(W)electrode employing a range of electrochemical teclmiques.Cyclic voltammetric and square-wave voltanunetric results revealed that the reduction of Bi(Ⅲ)was a one-step process,with the exchange of three electrons on a W electrode,and diffusion-controlled.The electrochemical curves showed two reduction peaks pertaining to the formation of Bi-Y alloy compounds,because of the co-reduction of Bi(Ⅲ)and Y(Ⅲ) by metallic Y deposited on the pre-deposited Bi-coated W electrode and reacting with Bi metal in molten LiCl-KCl. Furthermore,galvanostatic electrolysis was conducted using liquid Bi as cathode to extract yttrium at different current intensities,and the extractive products were analyzed by SEM,EDS and XRD.The results indicated that BiY intermetallic compotmd was formed in the molten LiCl-KCl-YCl3 system.     

Preparation and characterization of microspheres based on blend of poly(lactic acid) and poly(ɛ-caprolactone) with poly(vinyl alcohol) as emulsifier

In this paper, microspheres were prepared by oil-in-water (o/w) emulsion solvent evaporation method. Biodegradable polymer such as blend of poly (lactic acid) (PLA) and poly(?-caprolactone) (PCL) with certain compositions and characteristics was used to prepare the microspheres with poly(vinyl alcohol) (PVA) as an emulsifier. This study observed the microspheres particle’s size distribution at various concentrations of PVA (1%, 1.5%, 2%, and 2.5% PVA). The PVA volume variations effects during the process (50, 100, 150, 200, and 250 mL) were also observed. The blend of PLA and PCL is formed only by physical interaction between them. This can be seen from the FTIR spectrum which shows both PLA and PCL component. The microspheres physical size and appearance were observed by optical microscope (MO). The overall results of this study showed that the formula which used 50–150 mL of 2.5% polyvinyl alcohol produced the microspheres with the most uniform size distribution.     

Micellar and Mixed-Micellar Effects on Alkaline Hydrolysis of tris(1,10–phenanthroline)iron(II): Kinetic Exploration

The kinetics of alkaline hydrolysis of tris(1,10–phenanthroline)iron(II) has been studied in the presence of nonionic and mixed nonionic–ionic micellar media at 308 K. The effects of mixed-micellar environments of nonionic with ionic surfactants (C₁₂E₂₃/ATABs and C₁₂E₂₃/SDS) on the hydrolytic rate have been studied. The rate decreases monotonically with an increment of [C₁₂E₂₃]_T (total Brij 35 concentration) at constant [^?OH]₀ and has been discussed with the pseudo-phase micellar model. The rate also decreases with [C₁₂E₂₃]_T at a continuous addition of ionic surfactants (ATABs and SDS). The observed rate constant k_obs follows the empirical relation: k_obs = (k₀ + θK [C₁₂E₂₃]_T)/(1 + K [C₁₂E₂₃]_T) (where θ and K are empirical constants). The values of θ remain unaffected, whereas K decreases nonlinearly with [ATABs]_T in a mixed C₁₂E₂₃?ATAB micellar system. But the k_obs in a mixed C₁₂E₂₃–SDS micellar system is much lower than that of the C₁₂E₂₃–ATAB system and do not comply with any micellar kinetic models.     

Effects of Y (Ⅲ) Ions on the Fluorescence Properties of Ce(Ⅲ) Ion and the Organic Ligands in the Complex

The enhancement effects of Y ( Ⅲ) ions on the fluorescence of Ce ( Ⅲ) in Ce ( Ⅲ)-Y ( Ⅲ)-PMMA (polymethylmethacrylate ) or Ce ( Ⅲ)-Y ( Ⅲ)-PVC (polyvinyl chloride ) complex systems were observed. The influence of Y ( Ⅲ) ions on the emission spectra of PMMA ligands in PMMA-Y ( Ⅲ) and the fluorescent enhance- ment of Y( Ⅲ) on Ce( Ⅲ) emission in PMMA-Ce-Y by Y( Ⅲ) ion were studied. It was also of interest to note that when Y ( Ⅲ) ions were added into PMMA and into bpy(bipyridine ), respectively, the emission spectrum of PMMA ligands was split into fine structure bands by Y ( Ⅲ), and the fluorescence intensities of bpy ligands in bpy-Y ( Ⅲ) complexes were considerably increased.     

The Influence of β-Diketones on the Hydrolysis and Growth of Particles from Zirconium(IV) n-Propoxide

The influence of low ligand/Zr mole ratios ( = 0–0.1) on the hydrolysis and growth of oligomers from Zr(O ⁿ Pr)₄ modified with a series of -diketones (trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, dibenzoylmethane and dipivaloylmethane), and their subsequent aggregation to form uniform, dense spheres, has been investigated by light scattering and turbidometry. The addition of -diketones results in a large increase in the induction time, t _i (reduction in hydrolysis/condensation rates). A remarkable feature of the data is the dramatic reductions in rate observed even when a maximum of one in forty Zr–OR bonds have been replaced by the -diketone and are no longer available for hydrolysis or further condensation. The largest effect is observed with dibenzoylmethane, which increases t _i by a factor of 26 relative to acetylacetone.A mechanism rationalising the origin of the effect is discussed, which involves segregation of the -diketone ligands on the surface of the growing particle, with subsequent particle growth restricted to those sites not occupied by the chelating ligands.     

Effects of molecular structure and equivalent weight on facilitated transport of alkenes in Ag(I)–PFSI membranes

Fluxes and separation factors are reported for the facilitated transport of a variety of C₆ alkenes and dienes through two Ag(I)-exchanged polyfluorosulfonate ionomer membranes. For acyclic dienes, the largest separation factors are observed between those compounds with the greatest difference in spacing of the double bonds, and those with completely external versus internal double bonds. For cases where the spacing of the double bonds is the same, the compound with at least one terminal double bond exhibited a higher flux. The trends in fluxes for cyclic dienes is quite different; 1,4-cyclohexadiene is transported more slowly than cyclohexene while 1,3-cyclohexadiene is transported almost eight times more rapidly than cyclohexene. Methyl-substituents on the carbons comprising double bonds have minor effects on the transport properties. As anticipated, PFSI materials that contain more ion-exchange sites and absorb greater quantities of water exhibit slightly greater fluxes and separation factors for most alkene separations.     

Effects of pure AcOH and mixed AcOH–CS (CS?=?CH3CN and THF) solvents on the rate of cleavage of phthalic anhydride (PAn)

The values of pseudo-first-order rate constants (k _obs) for the acetolysis of phthalic anhydride (PAn) increase from 6.60?×?10^?7 to 31.5?×?10^?7?s^?1 with the increase in temperature from 30 to 50?°C. These values of k _obs give activation parameters ?H* and ?S* as 14.4?±?0.4?kcal?mol^?1 and ?39.1?±?1.3?cal?K^?1?mol^?1, respectively. The values of k _obs remain essentially unchanged with the increase in the content of CS (CS?=?CH₃CN or THF) from 0 to 40?% v/v in mixed AcOH?CCS solvents. These observations have been explained qualitatively.     

Action of Base on Methyl 6-Thio- (and 6-Deoxy-) 2-O-Methanesulfonyl-α-d-Glucopyranoside Derivatives1

Abstract

Treatment of methyl 4-O-benzoyl-3-O-tert-butyldiphenylsilyl-2-O-methanesulfonyl-6-thio-α-d-glucopyranoside (8) and its 6-deoxy analogue (11) with methanolic sodium methoxide, afforded methyl 2,3-anhydro-mannopyranoside derivatives as a consequence of an O₃ → O₄ TBDPS rearrangement. When the protecting group at C-3 was 2-methoxyethoxy methyl ether only deacylation and methanolysis of the methanesulfonyl group occurred.     

Catalyst-free,facile, and an efficient synthesis of α-aminonitriles employing Zn(CN)2 as an ecofriendly cyanating agent

An efficient and eco-friendly method has been developed for the synthesis of α-aminonitriles via one-pot three-component condensation of carbonyl compounds, amines, and Zn(CN)₂ under mild conditions. This protocol has the features of use of inexpensive, ecofriendly readily available, effective cyanide source, high yield, and simple work-up procedure.     

Synthesis and characterization of Pd(II)–vitamin B6 complex supported on magnetic nanoparticle as an efficient and recyclable catalyst system for C–N cross coupling of amides in deep eutectic solvents

Vitamin B₆–Pd(II) immobilized onto magnetic nanoparticles have been successfully prepared and applied for C–Xcross-coupling reactions with aryl halides in green deep eutectic solvents. The results prove that the Fe₃O₄@vitamin B₆–Pd(II) magnetic nanoparticles show high catalyst activity and good stability. It was also revealed that this complex can be recycled up to five times without any significant loss in catalytic activity.     

Synthesis of conformationally-constrained thio(seleno)hydantoins and α-triazolyl lactones from d-arabinose as potential glycosidase inhibitors

We have explored the rich structural diversity provided by an α-azido ester derived from d-arabinose as the source of sugar templates with reduced conformational flexibility. Using transient α-thioureido(selenoureido) esters we have prepared spiranic thio(seleno)hydantoins at the C-3 position of the sugar moiety. In this context, the first example of a stable spiranic α-lactam (or aziridinone) was isolated as a by-product in the hydrogenolysis of the starting α-azido ester. Furthermore, using copper(I)-catalyzed azido–alkyne cycloaddition (click chemistry), we have accessed bicyclic cis-fused α-triazolyl lactones fixed in the furanose form. Spiranic thiohydantoins turned out to be moderate, though selective, inhibitors of glycosidases, whereas their selenium isosters behaved as good free radical scavengers.     

Synthesis and Crystal Structures of Two Di-Cu(Ⅱ) Complexes Based on an Asymmetric Dinucleating Ligand

Two new dicopper(II) complexes [Cu2L(OAc)2](ClO4)·H2O(1) and [Cu2L(BPP)2]-(ClO4)(2) using an asymmetric dinucleating ligand HL and auxiliary ligands such as acetate(OAc) and bisphenyl phosphate(BPP) have been synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. Complex 1 crystallizes as blue single crystals that belong to the triclinic crystal system and P1 space group, while complex 2 crystallizes in a monoclinic P21/c space group. Single-crystal X-ray diffraction analysis reveals that the two copper ions in complexes 1 and 2 reside within the adjacent ligand compartments and are bridged by the endogenous phenoxo-O from ligand L and the introduction of two desired exogenous carboxylates or phosphates in the bidentate μ-1,3-bridged mode. The coordination geometries of Cu(1) and Cu(2) are both distorted square pyramids.     

Analogues of Moranoline and Mdl 73945. Methyl 6(5)-Deoxy-6(5)-(Morpholin-4-Yl)-α-D-Glycosides as Glucosidase Inhibitors

ABSTRACT

Methyl 2,3,4-tri-O-acetyl-6-O-(p-tolylsulfonyl)-α-D-glucopyranoside (6), or its iodo analogue 7, were subjected to nucleophilic displacement with morpholine to give 8, deacetylation of which gave methyl 6-deoxy-6-(morpholin-4-yl)-α-D-glucopyranoside (3). Similarly, 11, 12 and 21 were prepared. The 6-deoxy-6-iodo derivative 16 was subjected to nucleophilic displacement with morpholine and subsequent acetylation to give 15. Deacetylation of 15 gave 17. The kinetic studies for the inhibition of β-D-glucosidase from sweet almond and using o-nitrophenyl β-D-glucopyranoside as substrate exhibited a K _i value for 21 on the same order as 1-deoxynojirimycin whereas for 3, a K _i value of lesser order was observed.