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Polymer Beads (polymer + bead)
Selected AbstractsHollow Microtubes and Shells from Reactant-Loaded Polymer Beads,ANGEWANDTE CHEMIE, Issue 46 2009Rabih Makki Mit eigenem Antrieb: Wenn man mit Salzlösungen befüllte Agarose-Mikrokügelchen in eine Natriumsilicatlösung einbringt, so entstehen Röhren, die an einer anorganischen Schale anhaften (siehe Bild). Diese Röhren haben Innenradien von 3,,m aufwärts, können 0.5,mm lang werden und wachsen mit Geschwindigkeiten bis 50,,m,s,1. An Blasen hängende Röhren können eine gerichtete Bewegung der Kügelchen induzieren. [source] Surface-enhanced Raman scattering from analytes adsorbed on gold nanoparticles inside polymer beadsJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2004Mina Larsson Abstract Porous polymer beads with a large inner area were used as a stabilizing matrix for SERS-active gold particles. A commercially available ion exchanger (SOURCETM) was used together with HAuCl4. Absorbance measurements and an x-ray diffraction study confirmed that nanocrystalline gold was obtained in the polymer beads. Transmission electron microscope measurements were performed and showed that larger nanoparticles, 20,100 nm, were obtained on the surface, whereas in the interior smaller particles, approximately 2,10 nm, could be found. Three analytes, mercaptoethanesulfonate, mercaptopropionic acid and thiocyanate, were adsorbed on the gold particles inside the polymer beads. From all analytes enhanced Raman spectra could be obtained. The distribution of analytes adsorbed on gold nanoparticles was investigated by confocal Raman spectroscopy. SERS spectra from the analytes could be observed throughout the polymer bead, indicating a fairly uniform distribution of analytes adsorbed on gold nanoparticles. Copyright © 2004 John Wiley & Sons, Ltd. [source] Chitosan-Based Inverse Opals: Three-Dimensional Scaffolds with Uniform Pore Structures for Cell CultureADVANCED MATERIALS, Issue 29 2009Sung-Wook Choi Chitosan inverse opal scaffolds: Three-dimensional chitosan scaffolds with an inverse opal structure have been fabricated using a cubic close packed lattice of polymer beads as the template. The scaffolds have a uniform and interconnected pore structure as well as a fibrous morphology on the wall. They can be used as a model system for in vitro studies of cell culture and as clinically practical scaffolds for tissue engineering. [source] Fabrication of Graphene,Polymer Nanocomposites With Higher-Order Three-Dimensional ArchitecturesADVANCED MATERIALS, Issue 21 2009Jemma L. Vickery The use of aqueous dispersions of polystyrene sulfonate-stabilized graphene sheets for the fabrication of nanocomposites with higher-order 3D architectures is demonstrated using two examples of template-directed assembly. Macroscopic sponge-like polymer,graphene scaffolds are readily produced by directional freeze casting, while hollow graphene microspheres are prepared by electrostatically induced assembly on positively charged polymer beads. [source] Preparation of macroporous functionalized polymer beads by a multistep polymerization and their application in zirconocene catalysts for ethylene polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2003Chengbin Liu Abstract Macroporous functionalized polymer beads of poly(4-vinylpyridine- co -1,4-divinylbenzene) [P(VPy- co -DVB)] were prepared by a multistep polymerization, including a polystyrene (PS) shape template by emulsifier-free emulsion polymerization, linear PS seeds by staged template suspension polymerization, and macroporous functionalized polymer beads of P(VPy- co -DVB) by multistep seeded polymerization. The polymer beads, having a cellular texture, were made of many small, spherical particles. The bead size was 10,50 ,m, and the pore size was 0.1,1.5 ,m. The polymer beads were used as supports for zirconocene catalysts in ethylene polymerization. They were very different from traditional polymer supports. The polymer beads could be exfoliated to yield many spherical particles dispersed in the resulting polyethylene particles during ethylene polymerization. The influence of the polymer beads on the catalytic behavior of the supported catalyst and morphology of the resulting polyethylene was investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 873,880, 2003 [source] Surface-enhanced Raman scattering from analytes adsorbed on gold nanoparticles inside polymer beadsJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2004Mina Larsson Abstract Porous polymer beads with a large inner area were used as a stabilizing matrix for SERS-active gold particles. A commercially available ion exchanger (SOURCETM) was used together with HAuCl4. Absorbance measurements and an x-ray diffraction study confirmed that nanocrystalline gold was obtained in the polymer beads. Transmission electron microscope measurements were performed and showed that larger nanoparticles, 20,100 nm, were obtained on the surface, whereas in the interior smaller particles, approximately 2,10 nm, could be found. Three analytes, mercaptoethanesulfonate, mercaptopropionic acid and thiocyanate, were adsorbed on the gold particles inside the polymer beads. From all analytes enhanced Raman spectra could be obtained. The distribution of analytes adsorbed on gold nanoparticles was investigated by confocal Raman spectroscopy. SERS spectra from the analytes could be observed throughout the polymer bead, indicating a fairly uniform distribution of analytes adsorbed on gold nanoparticles. Copyright © 2004 John Wiley & Sons, Ltd. [source] Compartment size estimation with double wave vector diffusion-weighted imagingMAGNETIC RESONANCE IN MEDICINE, Issue 1 2008Martin A. Koch Abstract Double wave vector diffusion weighting uses gradients along two different directions between excitation and acquisition. It has been shown theoretically that for restricted diffusion the signal amplitude in such an experiment can depend on the angle between the two gradient vectors. The highest amplitude is obtained with antiparallel orientation, and the amplitude difference between parallel and antiparallel gradient orientations depends on the compartment size. The validity of this description is experimentally tested for water between polymer beads, for radish, and for porcine spinal cord, using a clinical MR system with limited gradient strength. The results indicate that the phenomenon is observable; however, the size of the signal difference is considerably diminished when compared with theory. This is attributed to violations of the approximating conditions underlying the theoretical description and to free diffusion contributions. It is concluded that the effect could successfully be used as a basis for developing a new noninvasive method for assessing cell size. Magn Reson Med, 2008. © 2008 Wiley-Liss, Inc. [source] Determination of the secondary structure of proteins in different environments by FTIR-ATR spectroscopy and PLS regressionBIOPOLYMERS, Issue 11 2008Yeqiu Wang Abstract The secondary structures of proteins (,-helical, ,-sheet, ,-turn, and random coil) in the solid state and when bound to polymer beads, containing immobilized phenyl and butyl ligands such as those as commonly employed in hydrophobic interaction chromatography, have been investigated using FTIR-ATR spectroscopy and partial least squares (PLS) methods. Proteins with known structural features were used as models, including 12 proteins in the solid state and 7 proteins adsorbed onto the hydrophobic surfaces. A strong PLS correlation was achieved between predictions derived from the experimental data for 4 proteins adsorbed onto the phenyl-modified beads and reference data obtained from the X-ray crystallographic structures with r2 values of 0.9974, 0.9864, 0.9924, and 0.9743 for ,-helical, ,-sheet, ,-turn, and random coiled structures, respectively. On the other hand, proteins adsorbed onto the butyl sorbent underwent greater secondary structural changes compared to the phenyl sorbent as evidenced from the poorer PLS r2 values (r2 are 0.9658, 0.9106, 0.9571, and 0.9340). The results thus indicate that the secondary structures for these proteins were more affected by the butyl sorbent, whereas the secondary structure remains relatively unchanged for the proteins adsorbed onto the phenyl sorbent. This study has important ramifications for understanding the nature of protein secondary structural changes following adsorption onto hydrophobic sorbent surfaces. This knowledge could also enable the development of useful protocols for enhancing the chromatographic purification of proteins in their native bioactive states. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 895,905, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Bioproduction of the aroma compound 2-Phenylethanol in a solid,liquid two-phase partitioning bioreactor system by Kluyveromyces marxianusBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Fang Gao Abstract The rose-like aroma compound 2-phenylethanol (2-PE) is an important fragrance and flavor ingredient. Several yeast strains are able to convert l -phenylalanine (l -phe) to 2-PE among which Kluyveromyces marxianus has shown promising results. The limitation of this process is the low product concentration and productivity primarily due to end product inhibition. This study explored the possibility and benefits of using a solid,liquid Two-Phase Partition Bioreactor (TPPB) system as an in situ product removal technique. The system applies polymer beads as the sequestering immiscible phase to partition 2-PE and reduce the aqueous 2-PE concentration to non-inhibitory levels. Among six polymers screened for extracting 2-PE, Hytrel® 8206 performed best with a partition coefficient of 79. The desired product stored in the polymer was ultimately extracted using methanol. A 3,L working volume solid,liquid batch mode TPPB using 500,g Hytrel® as the sequestering phase generated a final overall 2-PE concentration of 13.7,g/L, the highest reported in the current literature. This was based on a polymer phase concentration of 88.74,g/L and aqueous phase concentration of 1.2,g/L. Even better results were achieved via contact with more polymers (approximately 900,g) with the aqueous phase applying a semi-continuous reactor configuration. In this system, a final 2-PE concentration (overall) of 20.4,g/L was achieved with 1.4,g/L in the aqueous and 97,g/L in the polymer phase. The overall productivities of these two reactor systems were 0.38 and 0.43,g/L,h, respectively. This is the first report in the literature of the use of a polymer sequestering phase to enhance the bioproduction of 2-PE, and exceeds the performance of two-liquid phase systems in terms of productivity as well as ease of operation (no emulsions) and ultimate product recovery. Biotechnol. Bioeng. 2009; 104: 332,339 © 2009 Wiley Periodicals, Inc. [source] Improved reactor performance and operability in the biotransformation of carveol to carvone using a solid,liquid two-phase partitioning bioreactorBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2008Jenna L.E. Morrish Abstract In an effort to improve reactor performance and process operability, the microbial biotransformation of (,)- trans -carveol to (R)-(,)-carvone by hydrophobic Rhodococcus erythropolis DCL14 was carried out in a two phase partitioning bioreactor (TPPB) with solid polymer beads acting as the partitioning phase. Previous work had demonstrated that the substrate and product become inhibitory to the organism at elevated aqueous concentrations and the use of an immiscible second phase in the bioreactor was intended to provide a reservoir for substrates to be delivered to the aqueous phase based on the metabolic rate of the cells, while also acting as a sink to uptake the product as it is produced. The biotransformation was previously undertaken in a two liquid phase TPPB with 1-dodecene and with silicone oil as the immiscible second phase and, although improvement in the reactor performance was obtained relative to a single phase system, the hydrophobic nature of the organism caused the formation of severe emulsions leading to significant operational challenges. In the present work, eight types of polymer beads were screened for their suitability for use in a solid,liquid TPPB for this biotransformation. The use of selected solid polymer beads as the second phase completely prevented emulsion formation and therefore improved overall operability of the reactor. Three modes of solid,liquid TPPB operation were considered: the use of a single polymer bead type (styrene/butadiene copolymer) in the reactor, the use of a mixture of polymer beads in the reactor (styrene/butadiene copolymer plus Hytrel® 8206), and the use of one type of polymer beads in the reactor (styrene/butadiene copolymer), and another bead type (Hytrel® 8206) in an external column through which fermentation medium was recirculated. This last configuration achieved the best reactor performance with 7 times more substrate being added throughout the biotransformation relative to a single aqueous phase benchmark reactor and 2.7 times more substrate being added relative to the best two liquid TPPB case. Carvone was quantitatively recovered from the polymer beads via single stage extraction into methanol, allowing for bead re-use. Biotechnol. Bioeng. © 2008 Wiley Periodicals, Inc. [source] Degradation of xenobiotics in a partitioning bioreactor in which the partitioning phase is a polymerBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2003Brian G. Amsden Abstract Two-phase partitioning bioreactors (TPPBs) are characterized by a cell-containing aqueous phase and a second immiscible phase that contains toxic and/or hydrophobic substrates that partition to the cells at subinhibitory levels in response to the metabolic demand of the organisms. To date, the delivery phase in TPPBs has been a hydrophobic solvent that traditionally needed to possess a variety of important properties including biocompatibility, nonbioavailability, low volatility, and low cost, among others. In the present work we have shown that the organic solvent phase can be replaced by inexpensive polymer beads that function in a similar fashion as organic solvents, delivering a toxic substrate to cells based on equilibrium considerations. Specifically, 3.4 mm diameter beads of poly(ethylene-co-vinyl acetate) (EVA) were used to reduce the aqueous concentration of phenol in a bioreactor from toxic levels ( ,2,000 mg/L) to subinhibitory levels (,750 mg/L), after which Pseudomonas putida ATCC 11172 was added to the system and allowed to consume the total phenol loading. Thus, the beads absorbed the toxic substrate and released it to the cells on demand. The EVA beads, which could be reused, were able to absorb 14 mg phenol/g EVA. This work has opened the possibility of using widely mixed cultures in TPPB systems without concern for degradation of the delivery material and without concern of contamination. © 2003 Wiley Periodicals. Biotechnol Bioeng84: 399,305, 2003. [source] Operational concept for the improved synthesis of (R)-3,3'-furoin and related hydrophobic compounds with benzaldehyde lyaseBIOTECHNOLOGY JOURNAL, Issue 5 2006Marion B. Ansorge-Schumacher Dr. Abstract Biphasic reaction systems for enzyme catalysis are an elegant way to overcome limited solubility and stability of reactants and facilitate continuous processes. However, many synthetically useful enzymes are not stable in biphasic systems of water and organic solvent. The entrapment in polymer beads of polyvinyl alcohol has been shown to enable the stable operation of enzymes unstable in conventional biphasic reaction systems. We report the extension of this concept to continuous operation in a fluidised bed reactor. The enzyme benzaldehyde lyase was used for the continuous synthesis of enantiopure (R)-3,3'-furoin. The results show enhanced stability with half-life times under operation conditions of more than 100 h, as well as superior enzyme utilisation in terms of productivity. Furthermore, racemisation and oxidation of the product could be successfully prevented under the non-aqueous and inert reaction conditions. [source] Analysis of a Microbial Community Oxidizing Inorganic Sulfide and MercaptansBIOTECHNOLOGY PROGRESS, Issue 4 2001Kathleen E. Duncan Successful treatment of refinery spent-sulfidic caustic (which results from the addition of sodium hydroxide solutions to petroleum refinery waste streams) was achieved in a bioreactor containing an enrichment culture immobilized in organic polymer beads with embedded powdered activated carbon (Bio-Sep). The aerobic enrichment culture had previously been selected using a gas mixture of hydrogen sulfide and methyl mercaptan (MeSH) as the sole carbon and energy sources. The starting cultures for the enrichment consisted of several different Thiobacillispp. (T. thioparus, T. denitrificans, T. thiooxidans, and T.neopolitanus), as well as activated sludge from a refinery aerobic wastewater treatment system and sludge from an industrial anaerobic digester. Microscopic examination (light and SEM) of the beads and of microbial growth on the walls of the bioreactor revealed a great diversity of microorganisms. Further characterization was undertaken starting with culturable aerobic heterotrophic microorganisms (sequencing of PCR-amplified DNA coding for 16S rRNA, Gram staining) and by PCR amplification of DNA coding for 16S rRNA extracted directly from the cell mass, followed by the separation of the PCR products by DGGE (denaturing gradient gel electrophoresis). Eight prominent bands from the DGGE gel were sequenced and found to be closest to sequences of uncultured Cytophagales (3 bands),Gram-positive cocci (Micrococcineae), , proteobacteria (3 bands), and an unidentified , proteobacterium. Culturable microbes included several genera of fungi as well as various Gram-positive and Gram-negative heterotrophic bacteria not seen in techniques using direct DNA extraction. [source] | ||||||||||||||||