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Light Scattering Measurements (light + scattering_measurement)
Kinds of Light Scattering Measurements Selected AbstractsOnline Light Scattering Measurements as a Means to Assess Influence of Extrusion Parameters on Non-reactive Polymer Blend Morphology: Experimental Procedure and Preliminary ResultsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Christophe Serra Abstract The influence of extrusion parameters on the morphology of non-reactive blends has been investigated by means of online light-scattering measurements. A light-scattering device was especially designed to be mounted on a twin screw extruder at different locations along the barrel. The obtained light-scattering patterns were interpreted with respect to the variation of the processing parameters. Preliminary results show that there is little effect of the rotational speed, position along the screw and feed throughput on the morphology but a quite noticeable effect of the blend composition. These results were confirmed by SEM micrographs. On a étudié l'influence des paramètres d'extrusion sur la morphologie de mélanges non réactifs par des mesures de diffusion de la lumière en ligne. Un système de diffusion de la lumière a été spécialement conçu pour être monté sur une extrudeuse bi-vis à différents endroits le long du fourreau. Les modèles de diffusion de la lumière obtenus sont interprétés en tenant compte de la variation des paramètres de procédé. Les résultats préliminaires montrent le peu d'effet de la vitesse rotationnelle, de la position sur la vis et de la capacité d'alimentation sur la morphologie mais un effet assez appréciable de la composition du mélange. Ces résultats sont confirmés par des micrographes en microscopie électronique à balayage. [source] Susceptibility of isolated myofibrils to in vitro glutathionylation: Potential relevance to muscle functions,CYTOSKELETON, Issue 2 2010Chiara Passarelli Abstract In this study we investigated the molecular mechanism of glutathionylation on isolated human cardiac myofibrils using several pro-glutathionylating agents. Total glutathionylated proteins appeared significantly enhanced with all the pro-oxidants used. The increase was completely reversed by the addition of a reducing agent, demonstrating that glutathione binding occurs by a disulfide and that the process is reversible. A sensitive target of glutathionylation was ,-actin, showing a different reactivity to the several pro-glutathionylating agents by ELISA. Noteworthy, myosin although highly sensitive to the in vitro glutathionylation does not represent the primary glutathionylation target in isolated myofibrils. Light scattering measurements of the glutathionylated ,-actin showed a slower polymerisation compared to the non-glutathionylated protein and force development was depressed after glutathionylation, when the myofibrils were mounted in a force recording apparatus. Interestingly, confocal laser scanning microscopy of cardiac cryosections indicated, for the first time, the constitutive glutathionylation of ,-cardiac actin in human heart. Due to the critical location of ,-actin in the contractile machinery and to its susceptibility to the oxidative modifications, glutathionylation may represent a mechanism for modulating sarcomere assembly and muscle functionality under patho-physiological conditions in vivo. © 2009 Wiley-Liss, Inc. [source] Photography of the anterior eye segment according to Scheimpflug's principle: options and limitations , a reviewCLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 1 2009Alfred Wegener PhD Abstract Scheimpflug photography and densitometric image analysis are very precise techniques for light scattering measurement and biometry in the anterior segment of the eye. They provide reproducible data on the characteristics of the anterior eye segment in clinical and experimental studies and the set of data obtained allows discrimination of light scattering changes because of ageing, disease or toxic effects. The techniques can also be used to determine no-effect levels or maximally tolerable dosages of physical and chemical noxious factors. Several Scheimpflug cameras have been marketed, but the only cameras commercially available today are the Nidek EAS 1000 and the Oculus Pentacam. This review outlines the development of the technique and its introduction into ophthalmology. Furthermore, the application of the technique in clinical and experimental ophthalmology as well as in ocular toxicology are presented and discussed. [source] Scale-up development of high-performance polymer matrix for DNA sequencing analysisELECTROPHORESIS, Issue 19 2006Fen Wan Abstract Linear polyacrylamide (LPA) has been widely used as a replaceable separation matrix in CE. An increase in the molecular weight of the separation medium favors the separation of larger DNA fragments. In order to obtain ultrahigh-molecular-weight (UHMW) LPA, a "frozen" method was developed to synthesize the LPA homopolymer. This approach has three major advantages when compared with other existing routes of LPA synthesis: (i),long LPA chains could be obtained easily, with their average molecular weight (MW) being in the high 10,MDa range; (ii),the desired MW could be adjusted over a broad range by controlling the temperature and the concentration of initiators during synthesis; (iii),the product solution contains only a tiny amount of impurity besides the solvent and LPA. Both static and dynamic laser light scattering measurements were carried out to characterize the synthesized LPA in the buffer solution. The DNA sequencing matrix prepared from LPA using this method was studied and the results were compared with the newly developed commercial product POP7 from Applied Biosystems. It should be noted that this approach can be applied to synthesize other water-soluble polymers, resulting in UHMW products because the chain transfer constant is smaller at lower temperatures. [source] Simultaneous enhancement of cosmetic function and feel via molecular investigation of stickinessINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2006H. Kudoh Moisturizing performance is often a very important factor in cosmetics. However, incorporating high concentrations of moisturizing agents often causes products to become sticky, a feel that consumers dislike. We suspected that the reason why high moisturizer content generates strong stickiness is that the polar group of the molecule is exposed at the surface. Thus, we began with a hypothesis that stickiness could be prevented through coexistence with a substance minimizing the exposure of polar group. Using glycerine as a moisturizing agent, we screened a large number of conventional materials for reducing stickiness but failed to find an effective compound. We then considered the use of a polymer for this purpose and synthesized a custom-made polymer, polyoxyethylene methacrylate 2-hydroxyethyl methacrylate fluoroalkyl acrylate copolymer (Polymer SR). Our experiments revealed that Polymer SR reduces the stickiness of glycerine by forming a hydrophobic film without hindering moisturizing performance. To clarify the mechanism by which Polymer SR reduces stickiness, we investigated the interaction between the Polymer SR and glycerine in solution using NMR and static light scattering measurements. We learned that Polymer SR and glycerine form a complex via hydrogen bonding of glycerine that results in orientation of the hydrophobic group of Polymer SR towards the outside. Subjective sensory tests supported the hypothesis that this hydrophobic orientation was maintained on the dermal surface even after application to skin. We believe that by taking into account the intended function and feel our technique for reducing the stickiness of moisturizers can be adopted for use with other substances and will contribute to future cosmetic research. [source] Synthesis of high fluorescent silica hybrid materials by immobilization of orange peel extract in silica-silsesquioxane matrixJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2009I. Lacatusu Abstract Sol,gel chemistry can be easily modified to the changing needs of society to produce fine-tuned sol,gel nanostructured materials for relevant applications. In this context, there is an increasing need for natural and versatile raw materials as well as biocompatible compounds that could be extensively used as biomarkers for bioimaging in diagnosis or therapy. Silica-based materials are widely used in the field of biomedicine due to their chemical inertness and biocompatibility. In the present paper, orange peel extract was immobilized inside inorganic silica and hybrid silica-silsesquioxane polymeric networks. Silica and organo-modified silica matrices were synthesized through a templated sol,gel route of TEOS and an organosilsesquioxane (octaisobutyltetracyclo[7.3.3.15,11] octasiloxane- endo -3,7-diol), with D -glucose as template, and for comparison a non-ionic surfactant (tetraethylene glycol mono-hexadecyl ether) was also used. The bioactive properties of the molecules from orange peel extract were preserved after immobilization in both silica and silica-silsesquioxane networks. Moreover, the fluorescence properties were amplified by 10,20 times more than the native orange peel extract. The structural properties of the final materials have been studied by FT-IR, UV,Vis-NIR, and fluorescence spectroscopy. Dynamic light scattering measurements and transmission electron microscopy were used to estimate the size and morphology of the hybrid materials with orange peel extract immobilized in silica networks. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis of poly[N -isopropylacrylamide- g -poly(ethylene glycol)] with a reactive group at the poly(ethylene glycol) end and its thermosensitive self-assembling characterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Michihiro Iijima Abstract Poly[N -isopropylacrylamide- g -poly(ethylene glycol)]s with a reactive group at the poly(ethylene glycol) (PEG) end were synthesized by the radical copolymerization of N -isopropylacrylamide with a PEG macromonomer having an acetal group at one end and a methacryloyl group at the other chain end. The temperature dependence of the aqueous solutions of the obtained graft copolymers was estimated by light scattering measurements. The intensity of the light scattering from aqueous polymer solutions increased with increasing temperature. In particular, at temperatures above 40°C, the intensity abruptly increased, indicating a phase separation of the graft copolymer due to the lower critical solution temperature (LCST) of the poly(N -isopropylacrylamide) segment. No turbidity was observed even above the LCST, and this suggested a nanoscale self-assembling structure of the graft copolymer. The dynamic light scattering measurements confirmed that the size of the aggregate was in the range of several tens of nanometers. The acetal group at the end of the PEG graft chain was easily converted to the aldehyde group by an acid treatment, which was analyzed by 1H NMR. Such a temperature-induced nanosphere possessing reactive PEG tethered chains on the surface is promising for new nanobased biomedical materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1457,1469, 2006 [source] Synthesis of well-defined AB20 -type star polymers with cyclodextrin-core by combination of NMP and ATRPJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2005Yutaka Miura Abstract The synthesis of an AB20 -type heteroarm star polymer consisting of a polystyrene arm and 20-arms of poly(methyl methacrylate) or poly(tert -butyl acrylate) was carried out using the combination of nitroxide-mediated polymerization (NMP) and atom transfer radical polymerization (ATRP). The NMP of styrene was carried out using mono-6-[4-(1,-(2,,2,,6,,6,-tetramethyl-1,-piperidinyloxy)-ethyl)benzamido]-,-cyclodextrin peracetate (1) to afford end-functionalized polystyrene with an acetylated ,-cyclodextrin (,-CyD) unit (prepolymer 2) with a number-average molecular weight (Mn) of 11700 and a polydispersity (Mw/Mn) of 1.17. After deacetylation of prepolymer 2, the resulting polymer was reacted with 2-bromoisobutyric anhydride to give end-functionalized polystyrene with 20(2-bromoisobutyrol)s ,-CyD, macroinitiator 4. The copper (I)-mediated ATRP of methyl methacrylate (MMA) and tert -butyl acrylate (tBA) was carried out using macroinitiator 4. The resulting polymers were isolated by SEC fractionation to produce AB20 -type star polymers with a ,-CyD-core, 5. The well-defined structure of 5 with weight-average molecular weight (Mw)s of 13,500,65,300 and Mw/Mn's of 1.26,1.28 was demonstrated by SEC and light scattering measurements. The arm polymers were separated from 5 by destruction with 28 wt % sodium methoxide in order to analyze the details of their characteristic structure. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4271,4279, 2005 [source] Kinetics of the volume phase transition in poly(n -isopropylacrylamide) gels prepared under high pressureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2001Tadayosi Kitada Abstract New poly(N -isopropylacrylamide) gels were prepared under high pressure (ca. 200 MPa) during gelation. The preparation-pressure dependence of the deswelling speed of the gels was measured with a conventional T-jump method. The deswelling time of a gel rod 2.2 mm in diameter prepared at 193 MPa was about 200 s, 1000 times faster than that of a homogeneous poly(N -isopropylacrylamide) gel. Moreover, the collective diffusion coefficient, the thermal fluctuation, and the ensemble-average intensity of the swollen gel networks were obtained with dynamic light scattering measurements. Both the enthalpy and entropy of the gels were estimated from equilibrium swelling curves with the Flory,Huggins interaction parameter evaluated with mean field theory based on the Flory-type of the Gibbs free-energy formula. It was found that the networks of the gels had an inhomogeneous structure newly introduced by the preparation pressure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2315,2325, 2001 [source] Phase Transition Behavior of Novel pH-Sensitive Polyaspartamide Derivatives Grafted with 1-(3-Aminopropyl)imidazoleMACROMOLECULAR BIOSCIENCE, Issue 9 2006Kwangwon Seo Abstract Summary: New pH-sensitive polyaspartamide derivatives were synthesized by grafting 1-(3-aminopropyl)imidazole and/or O -(2-aminoethyl)- O,-methylpoly(ethylene glycol) 5000 on polysuccinimide for application in intracellular drug delivery systems. The DS of 1-(3-aminopropyl)imidazole was adjusted by the feed molar ratio, and the structure of the prepared polymer was confirmed using FT-IR and 1H NMR spectroscopy. Their pH-sensitive properties were characterized by light transmittance measurements, and the particle size and its distribution were investigated by dynamic light scattering measurements at varying pH values. The pH-sensitive phase transition was clearly observed in polymer solutions with a high substitution of 1-(3-aminopropyl)imidazole. The prepared polymers showed a high buffering capacity between pH 5 and 7, and this increased with the DS of 1-(3-aminopropyl)imidazole. The pH dependence of the aggregation and de-aggregation behavior was examined using a fluorescence spectrometer. For MPEG/imidazole- g -polyaspartamides with a DS of 1-(3-aminopropyl)imidazole over 82%, self aggregates associated with the hydrophobic interactions of the unprotonated imidazole groups were observed at pH values above 7, and their mean size was over 200 nm, while the aggregates of polymers were dissociated at pH values below 7 by the protonation of imidazole groups. These pH-sensitive polyaspartamide derivatives are potential basic candidates for intracellular drug delivery carriers triggered by small pH changes. Mean particle size change of MPEG/imidazole- g -polyaspartamide as pH is varied. [source] Supramolecular Nanocycles Comprising , -Cyclodextrin-click-Ferrocene Units: Rings of Rings of RingsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2010Maricica Munteanu Abstract We applied 1,3-dipolar cycloaddition to bind ethynylferrocene onto 6I-azido-6I-deoxycyclomaltoheptaose under microwave assisted conditions. The process was investigated by 1H NMR, FT-IR spectroscopy, and MALDI-TOF mass spectrometry. The ability of the synthesized compound to self-organize to cyclic supramolecular structures was investigated by dynamic light scattering measurements and cryo-transmission electron microscopy. [source] The Formation of Biodegradable Polymeric Micelles from Newly Synthesized Poly(aspartic acid)- block -Polylactide AB-Type Diblock CopolymersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 6 2004Hidetoshi Arimura Abstract Summary: A poly(aspartic acid)- block -polylactide (PAsp- block -PLA) diblock copolymer was synthesized through the polymerization of , -benzyl- L -aspartate- N -carboxyanhydride [Asp(OBzl)-NCA] with amino-terminating polylactide (NH2 -PLA) as a macroinitiator. The chain length of the PAsp segment could be easily controlled by changing the monomer/initiator ratio. Dynamic light scattering measurements of PAsp- block -PLA aqueous solutions revealed the formation of polymeric micelles. Changes in the micelles as a function of pH were investigated. The structure and formation of micelles of the poly(aspartic acid)- block -polylactide (PAsp- block -PLA) diblock copolymers synthesized here. [source] In situ monitoring of reaction-induced phase separation with modulated temperature DSCMACROMOLECULAR SYMPOSIA, Issue 1 2003Steven Swier Abstract A linearly polymerizing and network forming epoxy-amine system, DGEBA-aniline and DGEBA-MDA, respectively, will be modified with 20 wt% and 50 wt% of a high- Tg thermoplastic poly(ether sulphone) (Tg=223°C), respectively, both showing LCST-type demixing behavior. Reaction-induced phase separation (RIPS) in these modified systems is studied using Modulated Temperature DSC (MTDSC) as an in situ tool. Phase separation in the linear system can be probed by vitrification of the PES-rich phase, occurring at a higher conversion than the actual cloud point from light scattering measurements. The negative slope of the cloud point curve in a temperature-conversion-transformation diagram unambiguously shows the LCST-type demixing behavior of this system, while the relation between the composition/glass transition of the PES-rich phase and the cure temperature is responsible for the positive slope of its vitrification line. Phase separation in the network forming system appears as reactivity increases at the cloud point due to the concentration of reactive groups. Different mixture compositions alter the ratio between the rate of phase separation and the rate of reaction, greatly affecting the morphology. Information about this in situ developed structure can be obtained from the heat capacity evolutions in non-isothermal post-cures. [source] DLS-Based Fractal Analysis in Early Stage GelationPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2003Michael Abstract The fractal dimension of colloidal particles emerging from geling resorcinol/formaldehyde solutions is determined using a commercial apparatus for dynamic light scattering measurements. The method is considered particularly suited to quality control, e.g. in the production of colloid particles from sol-gel processes. [source] Online light scattering measurements: A method to assess morphology development of polymer blends in a twin-screw extruderPOLYMER ENGINEERING & SCIENCE, Issue 10 2002G. Schlatter Light scattering has proved itself an efficient technique to determine particle diameters in heterogeneous dilute dispersions in the micrometer range. Extrusion of polymer blends is expected to give rise to very small particles, typically in the range from hundreds of nanometers to tens of micrometers. A light scattering device developed in our laboratory has been used to study the morphology of polymer blends obtained in a twin-screw extruder. The main advantage of this technique is the immediate response obtained without any surface or interface modification that can occur during the sample preparation by using more conventional techniques like electron microscopy. To show the possible applications of this light scattering device, preliminary tests have been carried out. First, we present a comparison between experimental measurements and theoretical results for dilute systems. Second, we have investigated the effect of shear flow on the droplet deformation. Finally, we have studied the variations of the light scattering pattern for a reactive blend. [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] Crystallization of recombinant human growth hormone at elevated pressures: Pressure effects on PEG-induced volume exclusion interactionsBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Ryan L. Crisman Abstract Crystallization of recombinant human growth hormone (rhGH) at elevated pressures was investigated in the presence of 6,000 molecular weight poly(ethylene glycol; PEG-6000). Crystallization of rhGH at atmospheric pressure occurred at a protein concentration of 15,mg/mL in 6% PEG-6000. Crystallization did not occur in the same solutions at 250,MPa. In contrast, at a pressure of 250,MPa in the presence of 8% PEG-6000, rhGH readily crystallized from solutions containing 35,mg/mL rhGH, whereas amorphous precipitate formed in the same solutions at atmospheric pressure. Osmotic virial coefficients were determined from static light scattering measurements and combined with a hard-sphere activity coefficient model to predict rhGH activity coefficients as a function of pressure and PEG concentration. Predicted activity coefficients quantitatively matched those determined from equilibrium solubility measurements. The ability to adjust the thermodynamic non-ideality with pressure provides a valuable tool to study protein crystallization in addition to providing a methodology for obtaining crystals at elevated pressures. Biotechnol. Bioeng. 2010;107:663,672. © 2010 Wiley Periodicals, Inc. [source] | |||||||||||||||||||