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Fourier-transform Infrared Spectroscopy (fourier-transform + infrared_spectroscopy)
Selected AbstractsProtein,Protein Interaction of a Pharaonis Halorhodopsin Mutant Forming a Complex with Pharaonis Halobacterial Transducer Protein II Detected by Fourier-Transform Infrared Spectroscopy,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Yuji Furutani Pharaonis halorhodopsin (pHR) functions as a light-driven inward chloride ion pump in Natoronomonas pharaonis, while pharaonis phoborhodopsin (ppR; also called pharaonis sensory rhodopsin II, pSRII), is a light sensor for negative phototaxis. ppR forms a 2:2 complex with its cognate transducer protein (pHtrII) through intramembranous hydrogen bonds: Tyr199ppR,Asn74pHtrII and Thr189ppR,Glu43 pHtrII, Ser62pHtrII. It was reported that a pHR mutant (P240T/F250Y), which possesses the hydrogen-bonding sites, impairs its pumping activity upon complexation with pHtrII. In this study, effect of the complexation with pHtrII on the structural changes upon formation of the K, L1 and L2 intermediates of pHR was investigated by use of Fourier-transform infrared spectroscopy. The vibrational changes of Tyr250pHR and Asn74pHtrII were detected for the L1 and L2 intermediates, supporting that Tyr250pHR forms a hydrogen bond with Asn74pHtrII as similarly to Tyr199ppR. The conformational changes of the retinal chromophore were never affected by complexation with pHtrII, but amide-I vibrations were clearly different in the absence and presence of pHtrII. The molecular environment around Asp156pHR in helix D is also slightly affected. These additional structural changes are probably related to blocking of translocation of a chloride ion from the extracellular to the cytoplasmic side during the photocycle. [source] 2,7-Carbazolenevinylene-Based Oligomer Thin-Film Transistors: High Mobility Through Structural Ordering,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005N. Drolet Abstract We have fabricated organic field-effect transistors based on thin films of 2,7-carbazole oligomeric semiconductors 1,4-bis(vinylene-(N -hexyl-2-carbazole))phenylene (CPC), 1,4-bis(vinylene-(N,-methyl-7,-hexyl-2,-carbazole))benzene (RCPCR), N -hexyl-2,7-bis(vinylene-(N -hexyl-2-carbazole))carbazole (CCC), and N -methyl-2,7-bis(vinylene-(7-hexyl- N -methyl-2-carbazole))carbazole (RCCCR). The organic semiconductors are deposited by thermal evaporation on bare and chemically modified silicon dioxide surfaces (SiO2/Si) held at different temperatures varying from 25 to 200,°C during deposition. The resulting thin films have been characterized using UV-vis and Fourier-transform infrared spectroscopies, scanning electron microscopy, and X-ray diffraction, and the observed top-contact transistor performances have been correlated with thin-film properties. We found that these new ,-conjugated oligomers can form highly ordered structures and reach high hole mobilities. Devices using CPC as the active semiconductor have exhibited mobilities as high as 0.3,cm2,V,1,s,1 with on/off current ratios of up to 107. These features make CPC and 2,7-carbazolenevinylene-based oligomers attractive candidates for device applications. [source] Tris(8-hydroxyquinoline-5-sulfonate)aluminum Intercalated Mg,Al Layered Double Hydroxide with Blue Luminescence by Hydrothermal SynthesisADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Shuangde Li Abstract Blue luminescent hybrid materials (DDS,AQS(x%)/LDH) are successfully prepared by co-intercalating tris(8-hydroxyquinoline-5-sulfonate)aluminum anions (AQS3,) and dodecyl sulfonate (DDS,) with different molar ratios into Mg,Al layered double hydroxides (LDHs) by the hydrothermal and solution co-precipitation methods. A film of the material on a quartz substrate is obtained by the solvent evaporation method. The results show the blue luminescence is remarkably different from the pristine Na3AQS, which has cyan luminescence (ca. 450,470 nm vs. 495 nm). Furthermore, the hydrothermal product of DDS,AQS(66.67%)/LDH exhibits optimal luminous intensity and a significantly enhanced fluorescence lifetime. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy indicate that the cyan,blue luminescence transition is due to the isomerization of meridianal to facial AQS via ligand flip caused by a host,guest electrostatic interaction, in combination with the dispersion and pre-intercalation effect of DDS. The hydrothermal conditions can promote a more ordered alignment of the intercalated fac -AQS compared with alignment in the solution state, and the rigid LDHs environment can confine the internal mobility of AQS to keep the facial configuration stable. This stability allows a facile preparation of large amounts of blue luminous powder/film, which is a new type of inorganic,organic hybrid photofunctional material. [source] Biophysical characterization of the interaction of high-density lipoprotein (HDL) with endotoxinsFEBS JOURNAL, Issue 23 2002Klaus Brandenburg The interaction of bacterial endotoxins [lipopolysaccharide (LPS) and the ,endotoxic principle' lipid A], with high-density lipoprotein (HDL) from serum was investigated with a variety of physical techniques and biological assays. HDL exhibited an increase in the gel to liquid crystalline phase transition temperature Tc and a rigidification of the acyl chains of the endotoxins as measured by Fourier-transform infrared spectroscopy and differential scanning calorimetry. The functional groups of the endotoxins interacting with HDL are the phosphates and the diglucosamine backbone. The finding of phosphates as target groups is in accordance to measurements of the electrophoretic mobility showing that the zeta potential decreases from ,50 to ,60 mV to ,20 mV at binding saturation. The importance of the sugar backbone as further target structure is in accordance with the remaining negative potential and competition experiments with polymyxin B (PMB) and phase transition data of the system PMB/dephosphorylated LPS. Furthermore, endotoxin binding to HDL influences the secondary structure of the latter manifesting in a change from a mixed ,-helical/,-sheet structure to a predominantly ,-helical structure. The aggregate structure of the lipid A moiety of the endotoxins as determined by small-angle X-ray scattering shows a change of a unilamellar/inverted cubic into a multilamellar structure in the presence of HDL. Fluorescence resonance energy transfer data indicate an intercalation of pure HDL, and of [LPS],[HDL] complexes into phospholipid liposomes. Furthermore, HDL may enhance the lipopolysaccharide-binding protein-induced intercalation of LPS into phospholipid liposomes. Parallel to these observations, the LPS-induced cytokine production of human mononuclear cells and the reactivity in the Limulus test are strongly reduced by the addition of HDL. These data allow to develop a model of the [endotoxin]/[HDL] interaction. [source] Protein-Enabled Synthesis of Monodisperse Titania Nanoparticles On and Within Polyelectrolyte MatricesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Eugenia Kharlampieva Abstract Here, the results of a study of the mechanism of bio-enabled surface-mediated titania nanoparticle synthesis with assistance of polyelectrolyte surfaces are reported. By applying atomic force microscopy, surface force spectroscopy, circular dichroism, and in situ attenuated total reflection Fourier-transform infrared spectroscopy, structural changes of rSilC-silaffin upon its adsorption to polyelectrolyte surfaces prior to and during titania nanoparticle growth are revealed. It is demonstrated that the adhesion of rSilC-silaffin onto polyelectrolyte surfaces results in its reorganization from a random-coil conformation in solution into a mixed secondary structure with both random coil and , -sheet structures presented. Moreover, the protein forms a continuous molecularly thin layer with well-defined monodisperse nanodomains of lateral dimensions below 20,nm. It is also shown that rSilC embedded inside the polylelectrolyte matrix preserves its titania formation activity. It is suggested that the surface-mediated, bio-enabled synthesis of nanostructured materials might be useful to develop general procedures for controlled growth of inorganic nanomaterials on reactive organic surfaces, which opens new perspectives in the design of tailored, in situ grown, hybrid inorganic,organic nanomaterials. [source] Hydroxypropyl-,-Cyclodextrin-Capped Palladium Nanoparticles: Active Scaffolds for Efficient Carbon-Carbon Bond Forming Cross-Couplings in WaterADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Jaqueline Abstract A new approach for the preparation of palladium nanoparticles in water from a renewable source, 2-hydroxypropyl-,-cyclodextrin (,-HPCD), which acts both as a reductant and capping agent, is presented. The palladium nanoparticles were characterized by using dynamic light scattering (DLS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), which revealed the formation of spherical particles in the size range of 2,7,nm. Further analysis by Fourier-transform infrared spectroscopy (FT-IR) and 1H,NMR did not show covalent bonds between cyclodextrins and palladium nanoparticles, suggesting that ,-HPCD is only physically adsorbed on the nanoparticle surface, presumably through hydrophobic interactions which limit the mutual coalescence of nanoclusters. The catalytic activity was tested in Suzuki, Heck and Sonogashira reactions in neat water, providing good yields and selectivities of coupling products under very low Pd loadings (0.5,0.01,mol%). Remarkably, the nanocatalyst showed significant stability hence the aqueous phase remained active for four subsequent runs. The combination of a binding site for substrates (the HPCD cavity) and a reactive centre (Pd core) provides a potential to explore functional catalysis in aqueous medium. [source] Antibacterial activity of novel insoluble bead-shaped polymer-supported multiquaternary ammonium saltsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010E. Murugan Abstract This study describes the effect of antibacterial activity of newly reported five different novel insoluble bead-shaped polymer-supported multiquaternary ammonium salts (PM quats) viz., bis-quat, tris-quat (2 Nos.), tetrakis-quat, hexakis-quat containing two, three, four, and six quaternary ammonium groups, respectively. The presence of number of quaternary ammonium groups in each salt was established already through Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and chloride ion analyzes. The antibacterial activities of these five different PM quats against three different bacteria viz., Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa were investigated by serial dilution and spread plate method and compared the same with a monoquat containing single quaternary ammonium group. The extent of antibacterial activity has been measured in terms of colony forming units (CFU) at different time intervals. The observed results show that all the PM quats exhibited excellent-antibacterial activity against each bacterium. On the basis of the CFU values, the antibacterial activity was found to increase from bis-quat to hexakis-quat, which reveals that the activity of PM quats increases with increase in the number of quaternary ammonium groups. The mechanism of interaction of quats with bacterial cytoplasmic membrane has been explained as an adsorption-like phenomenon. The reusability of highly active hexakis-quat against Staphylococcus aureus was studied and the activity was found to reduce after first cycle. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Effect of Components Extracted from Okara on the Physicochemical Properties of Soymilk and Tofu TextureJOURNAL OF FOOD SCIENCE, Issue 2 2007Kyoko Toda ABSTRACT:, The physicochemical properties of soymilk and the texture of tofu were compared with regard to 2 kinds of soymilk, one of which was prepared by squeezing homogenates before heating and the other was prepared by squeezing after heating raw soymilk with okara, residue of soymilk production. Relative particulate protein content and viscosity were higher and pH was lower in the soymilk prepared by the latter method, in which liberated lipid bodies were decreased and more lipids were precipitated with protein after centrifugation, suggesting a change in the interaction between proteins and lipids. A difference in the distribution of proteins and lipids was also implied by analysis with a laser particle size analyzer. The breaking stress of tofu made with 0.30% glucono-delta-lactone increased in accordance with an increase in particulate protein. The calcium and magnesium contents increased in soymilk prepared by squeezing after heating with okara. Viscosity was slightly increased and pH decreased by adding calcium to the soymilk, but the particulate protein content and breaking stress of tofu did not increase significantly. To examine the effect of macromolecules, okara was extracted by boiling and dialyzed. Viscosity and particulate protein content in soymilk increased as the dialyzed extracts of the okara were added. The breaking stress of tofu was increased by adding the dialyzed extracts but excessive amounts of the extracts resulted in softer tofu. Spectra of Fourier-transform infrared spectroscopy and electrophoresis-separated patterns of proteins indicated that the dialyzed extracts contained mainly polysaccharides and the Basic 7S globulin protein. [source] Variations in fluid activity across the Etive thermal aureole, Scotland: evidence from cordierite volatile contentsJOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2008M. J. RIGBY Abstract The H2O and CO2 content of cordierite was analysed in 34 samples from successive contact metamorphic zones of the Etive thermal aureole, Scotland, using Fourier-transform infrared spectroscopy (FTIR). The measured volatile contents were used to calculate peak metamorphic H2O and CO2 activities. Total volatile contents are compared with recently modelled cordierite volatile saturation surfaces in order to assess the extent of fluid-present v. fluid-absent conditions across the thermal aureole. In the middle aureole, prior to the onset of partial melting, calculated aH2O values are high, close to unity, and measured volatile contents intersect modelled H2O,CO2 saturation curves at the temperature of interest, suggesting that fluid-present conditions prevailed. Total volatile contents and aH2O steadily decrease beyond the onset of partial melting, consistent with the notion of aH2O being buffered to lower values as melting progresses once free hydrous fluid is exhausted. All sillimanite zone samples record total volatile contents that are significantly lower than modelled H2O,CO2 saturation surfaces, implying that fluid-absent conditions prevailed. The lowest recorded aH2O values lie entirely within part of the section where fluid-absent melting reactions are thought to have dominated. Samples within 30 m of the igneous contact appear to be re-saturated, possibly via a magmatically derived fluid. In fluid-absent parts of the aureole, cordierite H2O contents yield melt,H2O contents that are compatible with independently determined melt,H2O contents. The internally consistent cordierite volatile data and melt,H2O data support the conclusion that the independent P,T estimates applied to the Etive rocks were valid and that measured cordierite volatile contents are representative of peak metamorphic values. The Etive thermal aureole provides the most compelling evidence, suggesting that the cordierite fluid monitor can be used to accurately assess the fluid conditions during metamorphism and partial melting in a thermal aureole. [source] Dissolution of artemisinin/polymer composite nanoparticles fabricated by evaporative precipitation of nanosuspensionJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2010Mitali Kakran Abstract Objectives An evaporative precipitation of nanosuspension (EPN) method was used to fabricate composite particles of a poorly water-soluble antimalarial drug, artemisinin, with a hydrophilic polymer, polyethylene glycol (PEG), with the aim of enhancing the dissolution rate of artemisinin. We investigated the effect of polymer concentration on the physical, morphological and dissolution properties of the EPN-prepared artemisinin/PEG composites. Methods The original artemisinin powder, EPN-prepared artemisinin nanoparticles and artemisinin/PEG composites were characterised by scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), dissolution testing and HPLC. The percentage dissolution efficiency, relative dissolution, time to 75% dissolution and mean dissolution time were calculated. The experimental drug dissolution data were fitted to various mathematical models (Weibull, first-order, Korsemeyer,Peppas, Hixson,Crowell cube root and Higuchi models) in order to analyse the release mechanism. Key findings The DSC and XRD studies suggest that the crystallinity of the EPN-prepared artemisinin decreased with increasing polymer concentration. The phase-solubility studies revealed an AL -type curve, indicating a linear increase in drug solubility with PEG concentration. The dissolution rate of the EPN-prepared artemisinin and artemisinin/PEG composites increased markedly compared with the original artemisinin powder. Conclusions EPN can be used to prepare artemisinin nanoparticles and artemisinin/PEG composite particles that have a significantly enhanced dissolution rate. The mechanism of drug release involved diffusion and erosion. [source] A phosphorus-containing thermotropic liquid crystalline copolyester with low mesophase temperature and high flame retardanceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2008Cheng-Shou Zhao Abstract A novel phosphorus-containing thermotropic liquid crystalline copolyester with flexible spacers (P-TLCP-FS) was synthesized by melt transesterification from p -acetoxybenzoic acid (p -ABA), terephthalic acid (TPA), ethylene glycol, and acetylated 2-(6-oxid-6H-dibenz(c,e) (1,2) oxaphosphorin 6-yl) 1,4-benzenediol (AODOPB). The chemical structure and properties of the obtained P-TLCP-FS were characterized by Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H-NMR), inherent viscosity measurements, differential scanning calorimetry (DSC), thermogravimetry (TGA), polarizing light microscopy (PLM), and X-ray diffraction (XRD) analysis. P-TLCP-FS had inherent viscosities of 0.92,1.12 dL/g and exhibited low and wide mesophase temperatures, ranging from 185 to 330 °C, which can match with the processing temperatures of most conventional polymers and high flame retardancy with a limiting oxygen index value of 70% and UL-94 V-0 rating. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5752,5759, 2008 [source] Thermogelling behaviors of poly(caprolactone- b -ethylene glycol- b -caprolactone) triblock copolymer in the presence of hyaluronic acidJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2008In Yong Kim Abstract In this article, we studied the effect of hyaluronic acid (HA) on thermogelation of poly(caprolactone- b -ethylene glycol- b -caprolactone) (PCL-PEG-PCL) aqueous solution designed as an injectable system for prevention of postsurgical tissue adhesion. The PCL-PEG-PCL triblock copolymers were simply synthesized by ring-opening polymerization of ,-caprolactone (CL) in the presence of PEG as a polymeric initiator. The synthesized copolymers were confirmed by proton nuclear magnetic resonance (1H-NMR) spectroscopy. Possible interactions between HA and PCL-PEG-PCL triblock copolymers in the blend were evaluated by Fourier-transform infrared spectroscopy (FTIR). The effect of HA on the micellization of PCL-PEG-PCL aqueous solution was investigated by dye solubilization method and electrophoretic lighting scattering (ELS) spectrophotometer. Also, the thermogelling behaviors of the PCL-PEG-PCL triblock copolymers in the presence of HA and their mechanism were investigated by test tube inverting method, 13C-NMR, 1H-NMR, Advanced Rheometic Expansion System (ARES), and differential scanning calorimetry (DSC). The PCL-PEG-PCL/HA blend aqueous solutions undergo the sol-gel-sol transition in response to an increase in temperature (10,60 °C) and the gelation of the PCL-PEG-PCL was rather accelerated by HA. Presumably, this accelerated gelation seems to arise from the attractive interactions between them and the effect of chain confinement in the micelle corona region. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3629,3637, 2008 [source] Examination of pigments on Thai manuscripts: the first identification of copper citrateJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2008Katherine Eremin Abstract Samples from Thai manuscripts dated to the 18th to 20th century were analyzed by Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR) to determine the pigments used. This suggested a change in palette from the 18th to 20th century, with use of imported pigments in the later manuscripts. In the 18th century, the main green used was an organic copper salt, which was replaced by emerald green and mixtures of Prussian blue with gamboge, chrome yellow and zinc yellow (zinc potassium chromate). Chrome yellow was used in addition to gamboge in one later 19th century manuscript. Similarly, indigo in the 18th century manuscripts was replaced by Prussian blue and then synthetic ultramarine in the 19th century manuscripts. Lead white was the main white pigment in all but one manuscript, which contained huntite, a magnesium calcium carbonate. Huntite also occurred in mixtures with other pigments in two other manuscripts. In all the works studied, red lead, vermilion and red earth were used for red, orange and pink shades and red earth in brown areas. The organic copper salt used in the 18th century gave good FTIR spectra but could not initially be matched with any published compound. X-ray diffraction (XRD) suggested this was a copper citrate phase, and examination of the literature showed that the FTIR spectra matched those published for a hydrated copper citrate. Raman spectra were obtained from this organic copper salt, which showed close agreement with those obtained from synthetic copper citrate. Copper citrate has not been identified previously as an artist's material, although its use has been postulated on the basis of historical texts. Minor copper formate and/or copper chloride were also identified by XRD and scanning electron microscopy (SEM) in some green samples containing copper citrate. Copyright © 2008 John Wiley & Sons, Ltd. [source] Effect of the combination of a benzophenone-type ultraviolet absorber with thermal stabilizers on the photodegradation of poly(vinyl chloride)JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 1 2010Xiuqin Xiang The effect of the combination of a UV absorber (Chimassorb 81) with different types of thermal stabilizers, including an organic calcium complex and an organotin mercaptide, on the photodegradation of poly(vinyl chloride) (PVC) was investigated by color difference measurements, UV,Vis spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric (TG) analysis, and viscosity-average molecular weight determination. Films of PVC containing 0.5 phr of Chimassorb 81, with and without 2 phr of a thermal stabilizer, were prepared by solution casting. Then the accelerated UV weathering of the films was carried out under xenon light with an irradiance of 0.51 W/(m2 · nm) at 65°C. The results showed that both Chimassorb 81 and the mixture of Chimassorb 81 with the organic calcium complex showed good behavior in inhibiting the photodehydrochlorination and photooxidation of PVC. In contrast, the combination of Chimassorb 81 and methyltin mercaptide significantly accelerated initial color development during the final 200 h of exposure because of the UV sensitivity of the organotin. Moreover, when Chimassorb 81 and the methyltin mercaptide were used together to stabilize PVC films, the expected antioxidant effect of the mixture was not observed, in contrast to the behavior found with other stabilized systems, perhaps because the Chimassorb 81 had been depleted by the methyltin mercaptide during the UV irradiation. The TG analysis revealed that ultraviolet irradiation had caused severe destruction of the PVC chains. However, addition of Chimassorb 81 or the combination of Chimassorb 81 with the organic calcium complex effectively prevented the destruction, as was demonstrated by changes in the activation energies for thermal degradation. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers [source] A Scalable Route to Highly Functionalized Multi-Walled Carbon Nanotubes on a Large ScaleMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2008Xianhong Chen Abstract A scalable and solvent-free chemical process to obtain highly functionalized and dispersible multi-walled carbon nanotubes is reported. Highly functionalized multi-walled carbon nanotubes have been prepared using in situ generated aryl diazonium salts in the presence of ammonium persulfate and 2,2,-azoisobutyronitrile by solvent-free techniques. In the Raman spectra of the resulting materials, characteristic peaks, the D- and G-bands, are shifted by about 10 cm,1 to lower frequencies. At the same time, the relative intensity ratios between the D- and G-bands increase in comparison to that in the spectrum of the purified product. Fourier-transform infrared spectroscopy reveals the presence of the functional groups on the surface. Transmission electron microscopy images directly confirm the significant build-up of sidewall organic moieties on the treated materials. The weight loss of various functional moieties determined by thermogravimetry,differential scanning calorimetry analysis is about 18,33%. The dispersibility of the functionalized materials in solvents, such as chloroform, tetrahydrofuran, and water, is obviously improved. [source] Protein,Protein Interaction of a Pharaonis Halorhodopsin Mutant Forming a Complex with Pharaonis Halobacterial Transducer Protein II Detected by Fourier-Transform Infrared Spectroscopy,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2008Yuji Furutani Pharaonis halorhodopsin (pHR) functions as a light-driven inward chloride ion pump in Natoronomonas pharaonis, while pharaonis phoborhodopsin (ppR; also called pharaonis sensory rhodopsin II, pSRII), is a light sensor for negative phototaxis. ppR forms a 2:2 complex with its cognate transducer protein (pHtrII) through intramembranous hydrogen bonds: Tyr199ppR,Asn74pHtrII and Thr189ppR,Glu43 pHtrII, Ser62pHtrII. It was reported that a pHR mutant (P240T/F250Y), which possesses the hydrogen-bonding sites, impairs its pumping activity upon complexation with pHtrII. In this study, effect of the complexation with pHtrII on the structural changes upon formation of the K, L1 and L2 intermediates of pHR was investigated by use of Fourier-transform infrared spectroscopy. The vibrational changes of Tyr250pHR and Asn74pHtrII were detected for the L1 and L2 intermediates, supporting that Tyr250pHR forms a hydrogen bond with Asn74pHtrII as similarly to Tyr199ppR. The conformational changes of the retinal chromophore were never affected by complexation with pHtrII, but amide-I vibrations were clearly different in the absence and presence of pHtrII. The molecular environment around Asp156pHR in helix D is also slightly affected. These additional structural changes are probably related to blocking of translocation of a chloride ion from the extracellular to the cytoplasmic side during the photocycle. [source] Coupling of Protonation Switches During Rhodopsin Activation,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2007Reiner Vogel Recent studies of the activation mechanism of rhodopsin involving Fourier-transform infrared spectroscopy and a combination of chromophore modifications and site-directed mutagenesis reveal an allosteric coupling between two protonation switches. In particular, the ring and the 9-methyl group of the all- trans retinal chromophore serve to couple two proton-dependent activation steps: proton uptake by a cytoplasmic network between transmembrane (TM) helices 3 and 6 around the conserved ERY (Glu-Arg-Tyr) motif and disruption of a salt bridge between the retinal protonated Schiff base (PSB) and a protein counterion in the TM core of the receptor. Retinal analogs lacking the ring or 9-methyl group are only partial agonists,the conformational equilibrium between inactive Meta I and active Meta II photoproduct states is shifted to Meta I. An artificial pigment was engineered, in which the ring of retinal was removed and the PSB salt bridge was weakened by fluorination of C14 of the retinal polyene. These modifications abolished allosteric coupling of the proton switches and resulted in a stabilized Meta I state with a deprotonated Schiff base (Meta ISB). This state had a partial Meta II-like conformation due to disruption of the PSB salt bridge, but still lacked the cytoplasmic proton uptake reaction characteristic of the final transition to Meta II. As activation of native rhodopsin is known to involve deprotonation of the retinal Schiff base prior to formation of Meta II, this Meta ISB state may serve as a model for the structural characterization of a key transient species in the activation pathway of a prototypical G protein-coupled receptor. [source] Study on superabsorbent composite.POLYMER COMPOSITES, Issue 8 2009In this work, the effects of different cation-exchanged montmorillonite on water absorbency of poly(acrylic acid- co -acrylamide)/montmorillonite/sodium humate (PAA-AM/MMT/SH) superabsorbent composite were systematically investigated under the same preparation conditions. The superabsorbents doped with different cation-exchanged montmorillonite were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy technologies. Swelling behaviors of developing superabsorbent composite in various cationic saline solutions (NaCl, CaCl2, and FeCl3) were also investigated. The water absorbencies of superabsorbent composite with 20 wt% MMT and 30 wt% SH are 638, 723, 682, and 363 g g,1 in distilled water for incorporating natural Na+ -MMT, Li+ -exchanged MMT, Ca2+ -exchanged MMT, and Al3+ -exchanged MMT, respectively. The results showed that the cation-exchange process had some obvious influences on final water absorbency of superabsorbent composite. NaCl, CaCl2, and FeCl3 solutions did not alter the swelling characteristics of the superabsorbent materials at a concentration of less than 0.01 mM, however, a concentration of greater than 0.1 mM caused a collapse in the swelling curves. The excellent swelling-reswelling-swelling behavior and lower swelling rate testified that Al3+ -exchanged MMT can act as an assistant crosslinker in the polymeric network. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Preparation and characterization of polypropylene/solid-state organomodified montmorillonite nanocompositesPOLYMER COMPOSITES, Issue 4 2008Sun Yu-hai A novel organomodified montmorillonite prepared by solid-state method and its nanocomposites with polypropylene were studied. The interaction between modifying agent and montmorillonite was investigated by X-ray diffraction (XRD) analysis, contact angle determination, and Fourier-transform infrared spectroscopy. The results showed that the modifying agent behaves as an effective intercalating agent, enlarging the interlayer spacing of montmorillonite and making montmorillonite more hydrophobic. Polypropylene/solid-state organomodified montmorillonite composites were prepared by melt-mixing method. The dispersion of the silicates was investigated by XRD analysis and transmission electron microscopy. It was found that the nanocomposites are formed with solid-state organomodified montmorillonite and polypropylene. The thermogravimetric analysis and differential scanning calorimetry results showed that the organoclay could enhance the thermal stability and decrease the relative crystallinity of polypropylene. Mechanical and rheological tests indicated that the organoclay improves the mechanical properties but has no obvious effect on rheological properties of polypropylene. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Evolution of structure in the softening/melting regime of miscible polymer mixingPOLYMER ENGINEERING & SCIENCE, Issue 6 2001Heidi E. Burch Structure development in the softening/melting processing regime is investigated using the model miscible blend poly(styrene-co-acrylonitrile) (SAN)/poly(methyl methacrylate) (PMMA). Feed materials of four different particle sizes are compounded to study their effects upon structure development. Fourier-transform infrared spectroscopy is used to help determine the normalized sample variance, a quantitative measure of mixing. The normalized sample variance is determined both as a function of sample size and as a function of feed particle size in an effort to assess the characteristic size scale(s) present in the blend at short mixing times. Results of these experiments indicate that the distribution of size scales in the softening regime is at least bimodal. Optical examination of pigmented mixtures reveals that this multimodality is due to the operation of the Scott/Macosko sheeting mechanism of morphology development, which was previously shown to be active in immiscible blends. This is contrary to the currently accepted laminar mixing model, which postulates the formation of a striated mixture while ignoring the softening/melting regime. [source] Preparation and characterization of microcapsulated red phosphorus and its flame-retardant mechanism in halogen-free flame retardant polyolefinsPOLYMER INTERNATIONAL, Issue 8 2003Qiang Wu Abstract Microcapsulated red phosphorus (MRP), with a melamine,formaldehyde resin coating layer, was prepared by two-step coating processes. The physical and chemical properties of MRP were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) and other measurements. The flame retardant action and mechanism of MRP in the halogen-free flame retardant (HFFR) polyolefins (PO) blends have been studied using cone calorimeter, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and dynamic FTIR spectroscopy. The results show that the MRP, which is coated with melamine,formaldehyde resin, has a higher ignition point, a considerably lower amount of phosphine evolution and of water absorption compared with red phosphorus (RP) itself. The data observed by cone calorimeter, LOI and TGA measurements from the PO/HFFR blends demonstrated that the MRP can decrease the heat release rate and effective heat of combustion, and increase the thermostability and LOI values of PO materials. The dynamic FTIR results revealed the flame-retardant mechanism that RP can promote the formation of charred layers with the P,O and P,C complexes in the condensed phase during burning of polymer materials. Copyright © 2003 Society of Chemical Industry [source] Plasma-modified poly(vinyl alcohol) membranes for the dehydrationof ethanolPOLYMER INTERNATIONAL, Issue 7 2003M Rafik Abstract Non-porous poly(vinyl alcohol) (PVA) membranes prepared by a cast-evaporating technique were covered with an allyl alcohol or acrylic acid plasma-polymerized layer. The wettability and the surface energy, as well as the chemical nature of the deposit, were assigned by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The ability of the modified membranes for dehydrating the water/ethanol azeotropic mixture by pervaporation was studied at 25, 40 and 60 °C. The best selectivity (, = 250 at 25 °C) was obtained in the case of the allyl alcohol plasma treatment. The results obtained are discussed on the basis of the hydrophilicity as well as in terms of the weakly crosslinked superficial layer that favoured the membrane swelling. Copyright © 2003 Society of Chemical Industry [source] Dispersion copolymerization of methyl methacrylate and acrylic acid in polar media: effects of reaction parameters on the particle size and size distribution of the copolymer microspheresPOLYMER INTERNATIONAL, Issue 5 2003Jin-Xia Huang Abstract Micron-size functional crosslinked poly(methyl methacrylate) (PMMA) particles with narrow size distribution in the range of 1,5 µm were prepared by dispersion copolymerization in polar media with poly(N -vinylpyrrolidone)(PVP) as steric stabilizer, 2,2,-azobisisobutyronitrile(AIBN) as initiator and ethylene glycol dimethylacrylate (EGDMA) as crosslinking agent. The effects of functional comonomer acrylic acid (AA) concentration, contents in AIBN, EGDMA and PVP, media polarity as well as reaction temperature on the particle size and size distribution were investigated. Particle size initially increased, and then decreased with increasing AA concentration in the range of 0.7,3.5 mol l,1, having a maximum of 5.01 µm at the concentration of 2.1 mol l,1, while size distribution became broader. This was regarded as the result of different roles of PAA in the process. Particle size increased with decreasing media polarity and stabilizer concentration, and with increasing initiator concentration and reaction temperature. The resulting particle shapes were observed by transmission electron microscopy and the presence of carboxyl groups on the surface of the particles was confirmed by Fourier-transform infrared spectroscopy. Copyright © 2003 Society of Chemical Industry [source] Ultraviolet-induced crosslinking of poly(vinyl alcohol) evaluated by principal component analysis of FTIR spectraPOLYMER INTERNATIONAL, Issue 10 2001R Miranda, Teresa M Abstract The crosslinking of poly(vinyl alcohol) (PVA) films under ultraviolet irradiation for between 1 and 4,h was studied in air at 25,°C in the presence of sodium benzoate by Fourier-transform infrared spectroscopy (FTIR) using the attenuated total reflectance technique (ATR). Principal component analysis (PCA) is a mathematical procedure that allows treatment of the entire infrared spectrum and is very appropriate for analysing the chemical modifications initiated by sodium benzoate which occur in PVA upon UV irradiation. By PCA it was possible to clarify the mechanism of crosslinking of PVA. From this FTIR,PCA study, it is suggested that a free radical arising from the photolysis of sensitizer would abstract a tertiary hydrogen atom from the polymer chain to yield a polymeric radical. This radical reacts with OH groups, leading to the formation of ether bonds between the polymeric chains and hence to crosslinking and insolubilization of the PVA. © 2001 Society of Chemical Industry [source] Degradation of high barrier ethylene,vinyl alcohol copolymer under mild thermal-oxidative conditions studied by thermal analysis and infrared spectroscopyPOLYMER INTERNATIONAL, Issue 6 2001José M Lagaron Abstract A study of the thermal-oxidative degradation of a high barrier ethylene,vinyl alcohol copolymer with 32,mol% of ethylene (EVOH) has been carried out by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) under mild temperature conditions above melting. It was found that time exposures of up to 11,h at temperatures between 9 and 33,°C above the EVOH melting point resulted in polymer weight losses of up to 3.6% with colour formation. The weight loss was faster at short times and slowed down with increasing exposure time. DSC showed a small decrease in crystallinity and melting point, melting-peak broadening and a slight increase in the glass transition temperature of the samples subjected to the more severe thermal-oxidative treatment. The FTIR experiments showed transformation of the vinyl alcohol hydroxyl groups into carbonyl groups and creation of double bonds. Changes in degradation kinetics and perhaps in mechanisms are thought to occur with increasing exposure time. Moreover, FTIR measurements suggest that transformation of the hydroxyl groups leads to a weakening of the overall hydrogen bonding strength in the degraded samples, and therefore a reduction in intermolecular cohesion can be anticipated. © 2001 Society of Chemical Industry [source] Catalytic performance of chitosan-Schiff base supported Pd/Co bimetallic catalyst for acrylamide with phenyl halidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2010Wang Li-xia Abstract The chitosan-Schiff base supported palladium and cobalt bimetallic complex was synthesized in a simple method and characterized by Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). It was found that the catalyst has great activity and stability in the coupling of acrylamide (AA) with the phenyl halide. The influence of various bimetallic catalysts, the different molar ratio of Co/Pd, the bases, the amount of the catalyst and base, and the molar ratio of iodobenzene/AA on the reaction were investigated. The results showed that the catalytic activity of the molar ratio of Co/Pd (3/1) was the best when the iodobenzene was used as a substrate. The yield of the cinnamamide did not change significantly after ten runs. It has been revealed that the catalyst was efficient for the reaction. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis of graft copolymers of xyloglucan and acrylonitrilePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2008Anuradha Mishra Abstract Xyloglucan (XG), a water-soluble food grade polysaccharide is reported as a substrate for the graft copolymerization of acrylonitrile (AN). XG was extracted from tamarind seed mucilage. Polymerization was initiated both by ceric ion in aqueous medium under N2 atmosphere and with microwave (MW) irradiation. The progress of the reaction was monitored gravimetrically. The effect of different reaction parameters such as monomer concentration, level of ceric ammonium nitrate/HNO3 (CAN) initiator, reaction time and temperature, and MW power on the percent grafting (PG) was studied. Grafting of polyacrylonitrile (PAN) onto XG was confirmed by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscope (SEM) techniques have been used to study the thermal and morphological changes in the materials. Copyright © 2007 John Wiley & Sons, Ltd. [source] GEOCHEMICAL AND ENGINEERING GEOLOGICAL PROPERTIES OF THE VOLCANIC TUFFS USED IN THE ETRUSCAN TOMBS OF NORCHIA (NORTHERN LATIUM, ITALY) AND A STUDY OF THE FACTORS RESPONSIBLE FOR THEIR RAPID SURFACE AND STRUCTURAL DECAYARCHAEOMETRY, Issue 2 2010P. CICCIOLI The geochemical and engineering geological properties of the tuffs used in the rock-cut cliff tombs of the Etruscan necropolis of Norchia were investigated to evaluate their susceptibility to different weathering agents and confirm their origin. For the first time, materials were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT,IR), thermogravimetric analyses (TGA, DGA and DTG), scanning electron microscopy (SEM,EDS) and energy-dispersive X-ray fluorescence (ED,XRF), and their different origins confirmed. Tests of material properties indicate that both tuffs are poorly durable, but one of them is less susceptible to weathering. Although tombs made with the more resistant material show limited surface weathering, they undergo severe structural damage because of stress release and plant root infiltration. This, combined with the microclimatic conditions established inside river canyons, can trigger rock falls, leading ultimately to the complete destruction of these tombs. [source] A biomimetic tubular scaffold with spatially designed nanofibers of protein/PDS® bio-blends,BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Vinoy Thomas Abstract Electrospun tubular conduit (4,mm inner diameter) based on blends of polydioxanone (PDS II®) and proteins such as gelatin and elastin having a spatially designed trilayer structure was prepared for arterial scaffolds. SEM analysis of scaffolds showed random nanofibrous morphology and well-interconnected pore network. Due to protein blending, the fiber diameter was reduced from 800,950,nm range to 300,500,nm range. Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results confirmed the blended composition and crystallinity of fibers. Pure PDS scaffold under hydrated state exhibited a tensile strength of 5.61,±,0.42,MPa and a modulus of 17.11,±,1.13,MPa with a failure strain of 216.7,±,13%. The blending of PDS with elastin and gelatin has decreased the tensile properties. A trilayer tubular scaffold was fabricated by sequential electrospinning of blends of elastin/gelatin, PDS/elastin/gelatin, and PDS/gelatin (EG/PEG/PG) to mimic the complex matrix structure of native arteries. Under hydrated state, the trilayer conduit exhibited tensile properties (tensile strength of 1.77,±,0.2,MPa and elastic modulus of 5.74,±,3,MPa with a failure strain of 75.08,±,10%) comparable to those of native arteries. In vitro degradation studies for up to 30 days showed about 40% mass loss and increase in crystallinity due to the removal of proteins and "cleavage-induced crystallization" of PDS. Biotechnol. Bioeng. 2009; 104: 1025,1033. © 2009 Wiley Periodicals, Inc. [source] Interaction of Cytidine 5,-Monophosphate with Au(111): An In Situ Infrared Spectroscopic StudyCHEMPHYSCHEM, Issue 9-10 2009Thomas Doneux Dr. Abstract Attracted to gold: The interaction of cytidine 5,-monophosphate (CMP) with gold surfaces is studied at the Au(111) | aqueous solution interface. In situ infrared spectroscopy studies show that cytidine 5,-monophosphate is chemisorbed on Au(111) through the N3 atom of the pyrimidine ring (see picture). The interaction of cytidine 5,-monophosphate (CMP) with gold surfaces is studied by means of in situ infrared spectroscopy and cyclic voltammetry at the Au(111) | aqueous solution interface. Similar to other nucleic acid components, cytidine 5,-monophosphate is chemisorbed on the surface at positive potentials, and the amount of adsorbed CMP increases with the potential. Subtractively normalized interfacial Fourier-transform infrared spectroscopy (SNIFTIRS) is used to identify the adsorbed and desorbed species. Upon electrochemical desorption, the molecules released in solution are unprotonated on the N3 atom. Striking similarities are found between the spectrum of adsorbed CMP and the solution spectrum of protonated CMP. The origin of such similarities is discussed. The results strongly suggest that chemisorption occurs through the N3 atom of the pyrimidine ring. A comparison is drawn with cytidine, whose electrochemical and spectroscopic behaviors are also investigated. [source] | |||||||||||||||||||||||||||||||