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Molecular Weight Range (molecular + weight_range)
Selected AbstractsParasitoid wasp sting: A cocktail of GABA, taurine, and ,-alanine opens chloride channels for central synaptic block and transient paralysis of a cockroach hostDEVELOPMENTAL NEUROBIOLOGY, Issue 8 2006Eugene L. Moore Abstract The wasp Ampulex compressa injects venom directly into the prothoracic ganglion of its cockroach host to induce a transient paralysis of the front legs. To identify the biochemical basis for this paralysis, we separated venom components according to molecular size and tested fractions for inhibition of synaptic transmission at the cockroach cercal-giant synapse. Only fractions in the low molecular weight range (<2 kDa) caused synaptic block. Dabsylation of venom components and analysis by HPLC and MALDI-TOF-MS revealed high levels of GABA (25 mM), and its receptor agonists ,-alanine (18 mM), and taurine (9 mM) in the active fractions. Each component produces transient block of synaptic transmission at the cercal-giant synapse and block of efferent motor output from the prothoracic ganglion, which mimics effects produced by injection of whole venom. Whole venom evokes picrotoxin-sensitive chloride currents in cockroach central neurons, consistent with a GABAergic action. Together these data demonstrate that Ampulex utilizes GABAergic chloride channel activation as a strategy for central synaptic block to induce transient and focal leg paralysis in its host. © 2006 Wiley Periodicals, Inc. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] A versatile electrophoresis system for the analysis of high- and low-molecular-weight proteinsELECTROPHORESIS, Issue 11 2003Christophe Tastet Abstract A new, versatile, multiphasic buffer system for high-resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins in the relative molecular weight range of 300,000,3000 Da is described. The system, based on the theory of multiphasic zone electrophoresis, allows complete stacking and destacking of proteins in the above Mr range. The buffer system uses taurine and chloride as trailing and leading ion, respectively, and Tris, at a pH close to its pKa, as the buffering counterion. Coupled with limited variation in the acrylamide concentration, this electrophoresis system allows to tailor the resolution in the 6,200 kDa Mr range, with minimal difficulties in the post electrophoretic identification processes. [source] Synthesis, characterization, and degradation of poly(ester-anhydride) for particulate deliveryISRAEL JOURNAL OF CHEMISTRY, Issue 4 2005Sweta Modi A series of poly(ester-anhydride) from poly(lactic acid) and poly(sebacic acid) have been synthesized and characterized. Poly(lactic acid) of molecular weight 2,550 Da has been synthesized from pharmaceutical grade lactic acid. The copolymers are in the molecular weight range of 3,000-15,000 Da, with the higher molecular weights obtained for the polymers with higher sebacic acid content. With increase in sebacic acid content, the melting point is also found to increase. The polymers with 50% or more poly(sebacic acid) content melt between 80 and 84 °C. These polymers have been formulated into microspheres and their degradation studied. Due to their biodegradability and the flexibility to alter their degradation profile, they find a wide application in drug delivery. [source] Studies on the condensation of depolymerized chitosans with DNA for preparing chitosan-DNA nanoparticles for gene delivery applicationsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Viola B. Morris Abstract High molecular weight chitosan (CS) was depolymerized by oxidative degradation with NaNO2 at room temperature to get 11 samples of CS derivatives of varying molecular weights with a view to assessing their effective molecular weight range for gene delivery applications. Viscosity studies indicated that the molecular weight of the depolymerized CS was proportional to the CS/NaNO2 ratio. The condensation behavior of DNA/CS complexes at various charge ratios was studied using UV spectroscopy, FTIR, CD, SEM, and AFM. The results indicated that CSs having very low molecular weights and high charge density exhibited strong binding affinity to DNA compared to high molecular weight CSs. However, the very low molecular weight (1.9,7.7 kDa) CSs were found to form aggregates easily even at very low charge ratios. On the other hand, CSs having medium molecular weight (49,51 kDa) and high degree of deacetylation (DD) gave stable uniform-sized nanoparticles. Biological studies carried out with the spherical nano-sized polyplexes formed between CS of 50 kDa (DD of 94%) and pEGFP plasmid DNA at N/P ratio of 5.0 showed excellent gene transfection efficiency at pH 6.5 in HeLa cells without cytotoxicity indicating their potential as genedelivery carriers. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Isolation and Identification of Bitter Peptides of Tryptic Hydrolysate of Soybean 11S Glycinin by Reverse-phase High-performance Liquid ChromatographyJOURNAL OF FOOD SCIENCE, Issue 8 2003I M.-R. ABSTRACT: The 21 peptides purified from the bitter fraction of tryptic hydrolysates of soybean 11S glycinin by using gel-permeation high-performance liquid chromatography (HPLC) and a series of 3 C18 reverse phase (RP)-HPLC were in the molecular weight range of 200-1400 Da and showed mostly the hydrophobicity of less than 1400 cal/mol. Although the primary structures of the bitter peptides from 11S glycinin were not exactly the same as those of the proglycinin, many bitter peptides were basic mimics of the common structure, indicating the significance of the primary structure of a peptide playing a role in the bitter taste perception. [source] Controlled radical polymerization of a trialkylsilyl methacrylate by reversible addition,fragmentation chain transfer polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2005M. N. Nguyen Abstract The reversible addition,fragmentation chain transfer (RAFT) polymerization of a hydrolyzable monomer (tert -butyldimethylsilyl methacrylate) with cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate as chain-transfer agents was studied in toluene solutions at 70 °C. The resulting homopolymers had low polydispersity (polydispersity index < 1.3) up to 96% monomer conversion with molecular weights at high conversions close to the theoretical prediction. The profiles of the number-average molecular weight versus the conversion revealed controlled polymerization features with chain-transfer constants expected between 1.0 and 10. A series of poly(tert -butyldimethylsilyl methacrylate)s were synthesized over the molecular weight range of 1.0 × 104 to 3.0 × 104, as determined by size exclusion chromatography. As strong differences of hydrodynamic volumes in tetrahydrofuran between poly(methyl methacrylate), polystyrene standards, and poly(tert -butyldimethylsilyl methacrylate) were observed, true molecular weights were obtained from a light scattering detector equipped in a triple-detector size exclusion chromatograph. The Mark,Houwink,Sakurada parameters for poly(tert -butyldimethylsilyl methacrylate) were assessed to obtain directly true molecular weight values from size exclusion chromatography with universal calibration. In addition, a RAFT agent efficiency above 94% was confirmed at high conversions by both light scattering detection and 1H NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5680,5689, 2005 [source] Nickel(II) and palladium(II) complexes with ,-dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Bernd Berchtold Abstract Nickel(II) and palladium(II) complexes with ,-dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2-cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo-Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3], and triethylaluminum (TEA) AlEt3. The palladium but not the nickel precatalysts could also be activated by B(C6F5)3 alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 107 gpolymer/molmetal · h. With the system B(C6F5)3/AlEt3, the activation process can be formulated as the following two-step reaction: (1) B(C6F5)3 and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C6F5)nEt3,n and B(C6F5)3,nEtn; and (2) Al(C6F5)nEt3,n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C6F5)Et2 is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1-dodecene as chain-transfer agents; the molar mass can be varied in the number-average molecular weight range from 2 · 103 to 9 · 105 g · mol,1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604,3614, 2002 [source] Study on Flow Induced Nano Structures in iPP with Different Molecular Weight and Resulting Strength BehaviorMACROMOLECULAR SYMPOSIA, Issue 1 2010Achim Frick Abstract Polypropylene samples in a wide molecular weight range between approx. 100,kg/mol to 1 600,kg/mol were processed by injection molding to thin walled micro specimens with respect to study shear induced crystallization phenomena under high shear rate and subsequently possible self reinforcement effects. The specimens nano structures were investigated and related deformation behavior under tensile studied. Novel morphologies have been detect and their micromechanical mechanism interpret and summarized. [source] Synthesis and characterization of hydrogels containing biodegradable polymersPOLYMER INTERNATIONAL, Issue 7 2008Adina Cretu Abstract BACKGROUND: Amphiphilic block and graft copolymers constitute a very interesting class of polymers with potential for biomedical applications, due to their special characteristics, which derive from the combination of properties of hydrophilic and hydrophobic moieties. In this work, the synthesis and biodegradation of poly(2-hydroxyethyl methacrylate)- graft -poly(L -lactide) are studied. RESULTS: The graft copolymers were synthesized using the macromonomer technique. In a first step, methacryloyl-terminated poly(L -lactide) macromonomers were synthesized in a wide molecular weight range using different catalysts. Subsequently, these macromonomers were copolymerized with 2-hydroxyethyl methacrylate in order to obtain a graft copolymer. These new materials resemble hydrogel scaffolds with a biodegradable component. The biodegradation was studied in hydrolytic and enzymatic environments. The influence of different parameters (molecular weight, crystallinity, ratio between hydrophilic and hydrophobic components) on the degradation rate was investigated. CONCLUSION: Based on this study it will be possible to tailor the release properties of biodegradable materials. In addition, the materials will show good biocompatibility due to the hydrophilic poly(2-hydroxyethyl methacrylate) hydrogel scaffold. This kind of material has potential for many applications, like controlled drug-delivery systems or biodegradable implants. Copyright © 2008 Society of Chemical Industry [source] Determination of wheat quality by mass spectrometry and multivariate data analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2002David Mark Gottlieb Multivariate analysis has been applied as support to proteome analysis in order to implement an easier and faster way of data handling based on separation by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. The characterisation phase in proteome analysis by means of simple visual inspection is a demanding process and also insecure because subjectivity is the controlling element. Multivariate analysis offers, to a considerable extent, objectivity and must therefore be regarded as a neutral way to evaluate results obtained by proteome analysis. Proteome analysis of storage proteins from the wheat gluten complex based on two-dimensional electrophoresis and analysis of the N-terminal sequence has revealed a protein homologous to ,-gliadins, tentatively associated with quality and within the molecular weight range 27,35,kDa. Further examinations of gliadin data based on mass spectrometry revealed that quality among wheat varieties could be determined by means of principal component analysis. Further examinations by interval partial least squares made it possible to encircle an overall optimal molecular weight interval from 31.5 to 33.7,kDa. The use of multivariate analysis on data from mass spectrometry has thus shown to be a promising technique to minimize the number of two-dimensional gels within the field of proteome analysis. Copyright © 2002 John Wiley & Sons, Ltd. [source] Chain stiffness of heteropolysaccharide from Aeromonas gum in dilute solution by dynamic light scatteringBIOPOLYMERS, Issue 6 2002Xiaojuan Xu Abstract Dynamic light scattering measurements have been made on 15 fractions of aeromonas (A) gum, an extracellular heteropolysaccharide produced by the strain Aeromonas nichidenii, with dimethylsulfoxide containing 0.2M lithium chloride as the solvent at 25°C. Data for the translational diffusion coefficient D covering a molecular weight range from 4.5 × 105 to 2.1 × 106 and ratios of the z -average radius of gyration ,s2,z1/2 to the hydrodynamic radius RH (calculated with previous ,s2,z data) suggest that the polymer behaves like a semiflexible chain in this solvent similar to the stiffness of cellulose derivatives. Thus the D data are analyzed on the basis of the Yamakawa,Fujii theory for the translational friction coefficient of a wormlike cylinder by coarse-graining the heteropolysaccharide molecule. Excluded-volume effects are taken into account in the quasi-two-parameter scheme, as was done previously for ,s2,z and [,] (the intrinsic viscosity) of A gum in the same solvent. The molecular weight dependence of RH is found to be explained by the perturbed wormlike chain with a persistence length of 10 nm, a linear mass density of 1350 nm,1, an excluded-volume strength parameter of 1.3 nm, and a chain diameter of 2.8 nm. These parameters are in substantial agreement with those estimated previously from ,s2,z and [,] data, demonstrating that the solution properties (D, ,s2,z, and [,]) of the heteropolysaccharide are almost quantitatively described by the current theories for wormlike chains in the molecular weight range studied. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 387,394, 2002 [source] External modulation of HT-1080 human fibrosarcoma cells improves urokinase productionBIOTECHNOLOGY PROGRESS, Issue 6 2008Shilpa S. Khaparde Abstract Urokinase was produced in a hollow fiber reactor using HT-1080 human fibrosarcoma cells. External modulation comprised replenishing of the medium in the extracapillary space, reducing the serum concentration in the extracapillary space from 10% to 2% and increasing flow rate of the circulating medium in the intracapillary space from 20 to 80 mL/min, each according to a specific protocol. More than sixfold increase was observed in the cumulative urokinase production for two and three medium replenishing modulations of the extracapillary space. After 15 days of continuous operation, the highest cumulative urokinase obtained was 1.63 × 106 PU/mL. SDS-PAGE and zymogram study established that the urokinase obtained was in the high molecular weight range of 54 kDa. The effect of external modulation on cumulative urokinase production was visualized as trajectories with respect to the ratio of lactic acid production rate (LPR) to the glucose uptake rate (GUR). The collective external modulation data showed two separate physiological regions in the cumulative urokinase vs. LPR/GUR plane. The HT-1080 cells exhibited two distinct morphologies in these regions that may be related to acidosis and metastasis. These regions also correspond to low and high urokinase productivity. [source] | ||||||||||||||||