Radiation-induced eco-compatible sulfonated starch/acrylic acid graft copolymers for sucrose hydrolysis

Radiation-induced graft-copolymers capable of hosting sulfonic groups and having more effective catalytic activity towards sucrose hydrolysis were prepared. Acrylic acid monomer (AA) was copolymerized with sulfonated starch (SS) at different compositions using ionizing radiation. Swelling behavior of the prepared copolymers at different environmental conditions was studied as well as thermal stability. The hydrolysis of sucrose to glucose and fructose by sulfonated starch/acrylic acid (SS/AA) graft copolymers was investigated. The kinetics of the reaction was determined for various (SS/AA) graft copolymers compositions and at a temperature range of 40-60 °C. The catalytic activity of the copolymers was found to be dependent on the reaction temperature and (SS/AA) graft copolymers compositions, it increases as the reaction temperature and sulfonated starch content (in the feed solution) increases. The obtained results suggest that the prepared SS/AA copolymers could be considered as catalytic reagent for sucrose hydrolysis.     

High-rate partial nitritation using porous poly(vinyl alcohol) sponge

Poly(vinyl alcohol) (PVA) has been utilized as a support material for the immobilization of nitrifying bacteria without the comprehensive survey of partial nitritation. In the present study, the activities of nitrifiers and the maximum nitrogen conversion rate of partial nitritation with PVA sponge-cubes were specified according to different conditions. The selective enrichment of ammonia-oxidizing bacteria (AOB) on PVA sponge-cubes was achieved by the competition between AOB and nitrite-oxidizing bacteria for dissolved oxygen. The efficiency of ammonia oxidation was proportional to the concentration of HCO₃ ^? with the molar ratio of HCO₃ ^?-C/NH₄ ⁺-N = 1.91 and a half of the ratio was applied to the further experiments to ensure stable partial nitritation. The maximum nitrogen conversion rate of partial nitritation was dependent on the volume, not the size of sponge-cubes. The partial nitritation showed the superior rate performance of 3.09 kg N/m³ day with the packing ratio of 32 % of 5 × 5 × 5 mm³ PVA sponge-cubes.     

Reusable flexible poly(vinyl alcohol)/chitosan-based polymer carbon dots composite film for acid blue 93 dye adsorption

The design and synthesis of water-insoluble chitosan-based polymer carbon dots [P(CS-g-CA)CDs] are described. A polyvinyl alcohol/chitosan-based polymer carbon dot [PVA/P(CS-g-CA)CDs] composite film was prepared using a simple casting method to be used in dye adsorption. The composite film was characterized using FT-IR, XPS, transparency, contact angle, and mechanical properties tests, which showed the successful incorporation of P(CS-g-CA)CDs into the film and also revealed that hydrogen bonding improved the mechanical properties of the PVA film. Furthermore, the composite film displayed substantially enhanced hydrophobicity, making it suitable for use in aqueous environments. In addition, the composite film exhibited stable adsorption of acid blue 93 (AB93) at pH 2–9, with an enhanced adsorption capacity of 433.24 mg/g. The adsorption obeyed Langmuir law with an efficiency of more than 89% even after five cycles. Therefore, the PVA/P(CS-g-CA)CDs film is a promising material for the treatment of organic dye-polluted wastewater.     

Amphiphilic poly(vinyl alcohol) derivatives as complexing agents for fenretinide

Poly(vinyl alcohol) (PVA) substituted with oleyl chains and tetraethyleneglycol monoethyl ether chains (TEGMEE) at 1.5% and 1% degrees of substitution respectively (mol of substituent to mol of hydroxyvinyl monomer) has previously been shown to self-assemble in water, providing aggregates selectively cytotoxic toward tumor cells vs normal cells. These polymers have also been shown to increase the long-term survival of nude mice injected with both human and murine neuroblastoma cell lines. In the present work, we changed the substitution degree of the oleyl chains on the poly(vinyl alcohol) backbone and maintained constant at 1% the degree of TEGMEE substitution. We evaluated the main physicochemical characteristics of the final polymers, their cytotoxicity toward tumor cells, and their complexing ability for hydrophobic molecules. The aim was to investigate the possibility of improving intrinsic antitumor efficacy of the polymer by changing the degree of oleyl chain substitution and further increase activity by complexation with antitumor drugs. The polymers were prepared at oleyl chain substitution degrees ranging from 0.5 to 3% (mol of substituent to mol of hydroxyvinyl monomer). The most active was again the 1.5% substituted polymer. It was further characterized by exhibiting the highest complexing ability toward hydrophobic molecules allowing the formation of a complex with fenretinide (HPR). The polymer-HPR complex was stable in aqueous environment and released the free drug prevalently in the presence of fluid hydrophobic phases. It was cytotoxic toward tumor cells with minimal activity toward normal cells. Antitumor activity exceeded that of the separate complex components resulting from the concomitant effect of the polymer and the HPR solubilized by complexation.     

Use of poly(vinylpyrrolidone) and poly(vinyl alcohol) for cryoultramicrotomy

Summary Specimens infused with or suspended in a mixture of 10–30% poly(vinylpyrrolidone) and 2.07–1.61m sucrose can often be more easily frozen-sectioned than those infused with sucrose alone. The pH of such a mixture can be efficiently adjusted to neutrality by using Na₂CO₃. Use of poly(vinylpyrrolidone) causes little or no increase in the background level of immunolabelling. Adsorption staining of ultrathin frozen sections with a mixture of uranyl acetate and poly(vinyl alcohol), i.e. a simple thin-embedding of the sections in such a mixture, produces positive staining effects that are often enough to delineate structures of many organelles. When OsO₄-treated frozen sections are stained with uranyl acetate and further adsorption-stained with a mixture of lead citrate and poly(vinyl alcohol), the overall staining effects are similar to those observed in double-stained conventional sections.A large portion of the findings was reported as a part of the author's presentation in the 11th International Congress on Electron Microscopy, held in Kyoto, Japan, in 1986.     

The molecular simulation of the miscibility,mechanical properties and physical cross-linking behavior of the poly(vinyl alcohol)/poly(acrylic acid) composited membranes

The miscibility and mechanical properties of poly vinyl alcohol (PVA) and poly acrylic acid (PAA)-composited membranes were studied with molecular simulation. The Flory–Huggins parameters (δ) were calculated to prove the good miscibility of PVA and PAA. The radial distribution functions of hydroxyl and carboxyl atoms and the average number of H-bonds were observed to indicate the degree of physical cross-linking between PVA and PAA. The influences of intermolecular physical cross-linking on the glass transition temperature and mechanical properties were estimated. The results revealed that the PVA/PAA membrane with a composition of 2:3 has the best plastic properties, which exhibits a good application value. All of the simulated results showed good agreement with the experimental data. It indicates that the method presented in this work has a promising application prospect.     

Imaging and thermal studies of wheat gluten/poly(vinyl alcohol) and wheat gluten/thiolated poly(vinyl alcohol) blends

The morphology of wheat protein (WG) blends with polyvinyl alcohol (PVA) and respectively with thiolated polyvinyl alcohol (TPVA) was investigated by atomic force (AFM) and transmission electron microscopy (TEM) as well as by modulated dynamic scanning calorimetry (MDSC). Thiolated additives based on PVA and other substrates were previously presented as effective means of improving the strength and toughness of compression molded native WG bars via disulfide-sulfhydryl exchange reactions. Consistent with our earlier results, AFM and TEM imaging clearly indicate that the addition of just a few mole percent of thiol to PVA was sufficient to dramatically change its compatibility with wheat protein. Thus, TPVA is much more compatible with WG and phase separates into much smaller domains than in the case of PVA, although there are still two phases in the blend: one WG-rich phase and another TPVA-rich phase. The WG/TPVA blend has phase domains ranging in size from 0.01 to 0.1 microm, which are roughly 10 times smaller than those of the WG/PVA blend. MDSC further illustrates the compatibilization of the protein with TPVA via the dependence of the transition temperatures on composition.     

Immobilization of hydrocarbon-oxidizing bacteria in poly(vinyl alcohol) cryogels hydrophobized using a biosurfactant

A simple biosurfactant-based hydrophobization procedure for poly(vinyl alcohol) (PVA) cryogels was developed allowing effective immobilization of hydrocarbon-oxidizing bacteria. The resulting partially hydrophobized PVA cryogel granules (granule volume 5 microl) contained sufficient number (6.5 x 10(3)) of viable bacterial cells per granule, possessed high mechanical strength and spontaneously located at the interface in water-hydrocarbon system. Such interfacial location of PVA granules allowed high contact of immobilized biocatalyst with hydrophobic substrate and water phase, thus providing bacterial cells with mineral and organic nutrients. As a result, n-hexadecane oxidation efficiency of 51% after 10-day incubation was achieved using immobilized biocatalyst. PVA cryogels with increased hydrophobicity can be used for immobilization of bacterial cultures performing oxidative transformations of water-immiscible organic compounds. Immobilization of in situ biosurfactant producing Rhodococcus bacteria into PVA cryogel is discussed. PVA cryogel granules with entrapped alkanotrophic rhodococcal cells were stable after 10-month storage at room temperature.     

Biosensor for the monitoring of hydrogen peroxide using poly(vinyl alcohol) membrane system

Summary A biosensor system for continuous on-line monitoring of hydrogen peroxide concentration was developed employing catalase and a poly(vinyl alcohol)/poly(tetra fluoro ethylene) bilayer membrane system, Catalase was entrapped between poly(vinyl alcohol) membrane layer and poly(tetra fluoro ethylene) membrane layer outside of the galvanic type DO probe. Since poly(vinyl alcohol) membrane has non-porous, hydrophilic characteristics, the difference in hydrogen peroxide concentration between inside and outside of the membrane was therefore approximately 100 times. The developed hydrogen peroxide sensor has a wide linear range of hydrogen peroxide sensing more than 140 mM and favourable dynamic response characteristics. The sensor showed also good operational stability, rapid response time, and long life time.     

Swelling behavior of poly(vinyl alcohol) cryogels employed as matrices for cell immobilization

Poly(vinyl alcohol) cryogels are prepared from aqueous solutions of the polymer by freezing and thawing and are employed as matrices for cell immobilization. The swelling behavior of these macroporous gel carriers in pure water and in solutions of certain compounds (salts, amino acids, and glucose) was studied to elucidate the osmotic properties of the cryogels during long-term exposure to aqueous media. It was shown that after the initial sol fraction was washed out, the residual gel matrix possessed high stability even at extreme pH conditions (acid or alkali concentration up to 1.0 mol l⁻¹) or in the presence of strong chaotropic salts such as sodium rhodanide. Although the macroporous supermolecular structure of the carriers under consideration underwent certain changes as a result of aging processes during prolonged washing of the gel, the high porous morphology of the material was retained.     

Preparation, characterization, and properties of chitosan-g-poly(vinyl alcohol) copolymer

The graft copolymer chitosan-g-poly(vinyl alcohol), with nontoxicity, biodegradability, and biocompatibility, was prepared by a novel method. The copolymer with porous net structure was observed by scanning electron microscopy (SEM). It is a potential method to combine chitosan with the synthetic polymers. The grafting reactions were conducted with various poly(vinyl alcohol) (PVA)/6-O-succinate-N-phthaloyl-chitosan (PHCSSA) feed ratios to obtain chitosan-g-poly(vinyl alcohol) copolymers with various PVA contents. The chemical structure of the chitosan-g-poly(vinyl alcohol) was characterized by Fourier transform infrared and nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and SEM were also detected to characterize the copolymer.     

Immobilization of biocatalysts with poly(vinyl alcohol) supports.

Two polymer materials, poly(vinyl alcohol) (PVA) superfine fibers and photocrosslinkable PVA bearing styrylpyridinium groups, have been developed to immobilize biocatalysts. The former has a large surface consisting of relatively large-size pores and the fibers can immobilize a large amount of biocatalyst on their surface by ionic interaction. The latter entraps many kinds of biocatalysts by cyclodimerization caused by visible light irradiation. The biocatalysts on/in these supports maintain high activity and thermal stability. These materials can easily be formed into various shapes suitable for various applications. A new bioreactor system was constructed for evaluating a variety of biocatalysts and supports.     

Structural chemistry of sulfonated fluorobenzylphosphonate salts. I

A study of the salts of 4-fluoro-3-sulfobenzylphosphonic acid has resulted in the synthesis of two new compounds with unusual layered structures. The crystal structures of these salts and the parent acid have been determined by single crystal X-ray methods. Crystal data: 4-F-3-SO₃H-C₆H₃CH₂PO₃H₂·H₂O: triclinic, space group

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for 1519 observations (l>3σ(l)) and 182 variables; [Ni(NH₃)₂(H₂O)₄]₃(4-F-3-SO₃-C₆H₃-CH₂PO₃)₂·4H₂O: triclinic, space group

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for 2689 observations (l>3σ(I)) and 511 variables: Na₃(4-F-3-SO₃-C₆H₃CH₂PO₃)- 8.5H₂O: monoclinic, C2/c, Z = 8, A = 25.636(4), B = 6.218(4), C = 24.136(2) Å, β = 98.33(1)°, V = 3807(3) ų, R(F) = 0.047 for 2262 observations (I>2;3σ(I)) and 254 variables. The parent acid monohydrate crystallizes in layers with the acidic groups directed to the faces of the layer. The water molecules are in between the layers hydrogen-bonded to the sulfonate oxygen atoms. The nickel salt contains three independent cations, each of which is hexacoordinated to a mixture of water and ammonia molecules. Thus, there is no direct coordination of the nickel by either the sulfonate or phosphonate oxygen atoms. The structure has alternating layers, the first formed by the anions and one of the nickel complexes, and the second by the other two complexes and the free water molecules. The sodium salt also has the anions arranged in layers but with an interpenetrating three-dimensional network of ionic and hydrogen bonds involving the cations and water molecules. The sodium ions are coordinated to a mixture of sulfonate oxygen atoms and bridging water molecules in irregular six-fold environments. These structures are discussed in terms of the coordination behavior of the difunctional anions in the context of known monofunctional phosphonate and sulfonate compounds.     

Effects of gibberellic acid on sucrose accumulation and sucrose biosynthesizing enzymes activity during banana ripening

During banana ripening there is a massive conversion into sugars, mainly sucrose, which can account for more than 10% of the fresh weight of the fruit. An ethylene burst is the trigger of the banana ripening process but there is evidence that other compounds can act as modulators of some biochemical pathways. As previously demonstrated, gibberellic acid (GA₃) can impair the onset of starch degradation and affect some degradative enzymes, but effects on the sucrose biosynthetic apparatus have not yet been elucidated. Here, the activity and amount of sucrose synthase (SuSy; E.C. 2.4.1.13) and sucrose–phosphate synthase (SPS; E.C. 2.4.1.14), respiration rates, ethylene production, and carbohydrate levels, were evaluated in GA₃-infiltrated and non-infiltrated banana slices. The exogenous supply of gibberellin did not alter the respiration or the ethylene profile but delayed sucrose accumulation by at least 2 days. While SuSy activity was similar in control and treated slices, SPS increase and sucrose accumulation was related in treated slices. Western blotting with specific antiserum showed no apparent effects of GA₃ on the amount of SuSy protein, but impaired the increase in SPS protein during ripening. The overall results indicate that although GA₃ did not block carbohydrate mobilisation in a irreversibly way, it clearly affected the triggering of starch breakdown and sucrose synthesis. Also, the delayed sucrose accumulation in GA₃-infiltrated slices could be explained by the disturbance of SPS activity. In conclusion, gibberellins can play an important role during banana ripening and our results also reinforce the idea of multiple regulatory components in the ripening pathway, as evidenced by the GA₃ effects.     

Electrospinning of poly(vinyl alcohol)-water-soluble quaternized chitosan derivative blend

Defect free mats containing a cationic polysaccharide, chitosan derivative such as N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC), have been prepared using electrospinning of an aqueous solution of poly(vinyl alcohol) (PVA)-HTCC blends. HTCC, a water-soluble derivative of chitosan, was synthesized via the reaction between glycidyl-trimethylammonium chloride and chitosan. Solutions of PVA-HTCC Blends were electrospun. The morphology, diameter and structure of the produced electrospun nanofibres were examined by scanning electron microscopy (SEM). The average fibre diameter was in the range of 200-600 nm. SEM images showed that the morphology and diameter of the nanofibres were mainly affected by weight ratio of the blend and applied voltage. The results revealed that increasing HTCC content in the blends decreases the average fibre diameter. These observations were discussed on the basis of shear viscosities and conductivities of the spinning solutions. Microbiological assessment showed that the PVA-HTCC mats have a good antibacterial activity against Gram-positive bacteria, Staphylococcus aureus, and Gram-negative bacteria, Escherichia coli.     

Poly(vinyl alcohol) functionalized poly(dimethylsiloxane) solid surface for immunoassay

In this communication, we describe a simple and robust method for the covalent bonding of poly(vinyl alcohol) (PVA) on a silanized poly(dimethylsiloxane) (PDMS) surface. Nonspecific adsorption of proteins via hydrophobic-hydrophobic interactions of the PVA-coated surface is greatly reduced, and biomolecules can be rapidly anchored on the PVA-coated surface with high loading and uniformity. On the basis of a sandwich immunoassay with the anti-rabbit IgG and IgG pair as a model, the detection limit for IgG is down to 1 pg/mL with linearity up to 11 microg the levels often encountered in biological, forensic, and environmental samples.     

Phototriggered DNA complexation and compaction using poly(vinyl alcohol) carrying a malachite green moiety

Photoinduced DNA compaction was performed using the interaction of DNA with a photoresponsive random copolymer of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG). Although PVAMG does not have any affinity for DNA under dark conditions, it undergoes photoionization upon exposure to UV light, consequently resulting in a cationic binding site for DNA. Electrophoresis results demonstrated that irradiation of PVAMG retarded the DNA bands due to their complexation, whereas the bands remained unchanged under dark conditions. The binding of PVAMG to DNA occurs at a cationic site/DNA phosphate ratio of approximately 0.036. Single-molecule observations of DNA by fluorescence microscopy revealed that irradiation of PVAMG induced a coil-globule transition in the DNA molecule. Complete compaction of DNA has been accomplished at a cationic site/DNA phosphate ratio >8.0, indicating that PVAMG offers an effective system to photochemically trigger DNA compaction.     

The photocycle of bacteriorhodopsin immobilized in poly(vinyl alcohol) film

The kinetics of photoelectric and optical signals were measured on samples containing oriented purple membranes immobilized in a poly(vinyl alcohol) film and on purple membranes introduced into a PVA-H2O mixture. The bacteriorhodopsin photocycle in the PVA-H2O mixture was complete. The only observed changes were the slowing down of the optical and electrical signals in relation to the M412-O640 and O640-bRall-trans steps. In the PVA film the O640 intermediate disappeared and a negative photoelectric signal appeared.