Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.2.42 (DTA)
 1,693 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interaction of poly(ethylene oxide) (PEO, 600 kDa) with fumed silica A-300 (SBET = 316 m2/g) was investigated under different conditions using adsorption, infrared (IR), thermal analysis (TG-DTA), AFM, and quantum chemical methods. The studied dried silica/PEO samples were also carbonized in a flow reactor at 773 K. The structural characteristics of fumed silica, PEO/silica, and pyrocarbon/fumed silica were investigated using nitrogen adsorption-desorption at 77.4 K. PEO adsorption isotherm depicts a high affinity of PEO to the fumed silica surface in aqueous medium. PEO adsorbed in the amount of 50 mg per gram of silica (PEO monolayer corresponds to CPEO approximately 190 mg/g) can disturb approximately 70% of isolated surface silanols. However, at the monolayer coverage, only 20% of oxygen atoms of PEO molecules take part in the hydrogen bonding with the surface silanols. An increase in the PEO amount adsorbed on fumed silica leads to a diminution of the specific surface area and contributions of micro- (pore radius R < 1 nm) and mesopores (1 < R < 25 nm) to the pore volume but contribution of macropores (R > 25 nm) increases with CPEO. Quantum chemical calculations of a complex of a PEO fragment with a tripple bond SiOH group of a silica cluster in the gas phase and with consideration for the solvent (water) effect show a reduction of interaction energy in the aqueous medium. However, the complex remains strong enough to provide durability of the PEO adsorption complexes on fumed silica; i.e., PEO/fumed silica nanocomposites could be stable in both gaseous and liquid media.
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PMID:Interaction of poly(ethylene oxide) with fumed silica. 1546 96

The effect of nanosized Al2O3/ZnO fillers on the interactions in PEO-NaSCN polymer electrolytes has been studied by FT-IR, XRD, and DTA measurements. The experimental results are discussed according to the grain boundary effect, the principle of Lewis acid-base, and epitaxial effect. It is shown that the hard Lewis acid centers on the surface of Al2O3 exhibit strong interactions with ether oxygens in PEO, even with ether oxygens that coordinated to Na+. Therefore, the modes of the interaction of Al2O3 with PEO-NaSCN electrolytes are dependent on the salt content. Al2O3 cannot influence the ionic association in P(EO)8NaSCN electrolyte, but do reduce significantly the solvating ability of PEO toward NaSCN in P(EO)60NaSCN electrolyte. However, NaSCN in P(EO)20NaSCN-30%Al2O3 nanocomposite appears as a state that resembles the situation of NaSCN in PEO amorphous phase. In contrast with Al2O3, the epitaxial effect of ZnO is not found in the interested systems where only weaker interaction is observed between ZnO and ether oxygen, and the modes of interaction of ZnO with PEO-NaSCN electrolytes are hardly related to the salt content. In addition, the soft Lewis acid groups on ZnO surface exhibit stronger complexation with SCN- in PEO-NaSCN electrolytes, and both can form the complex anion ZnO...SCN-.
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PMID:Interactions of nanosized Al2O3 and ZnO with poly(ethylene oxide)-NaSCN polymer electrolytes. 1685 Dec 65

Clay-PEO nanocomposites can have large electrical conductivities that make them potential electrolyte materials for rechargeable lithium batteries, but the origin of these large conductivities, especially for Li-containing materials, is poorly understood. This paper presents X-ray diffraction (XRD), TGA-DTA, and (7)Li and (23)Na NMR data for PEO nanocomposites made with natural (SWy-1) and synthetic (MNTS) montmorillonite clays that provide new insight into interlayer structure. An increase in basal d(001)-spacings demonstrates successful intercalation of PEO in all samples, and X-ray line narrowing shows that this intercalation improves the layer stacking order. The basal spacings of 17.9-19.4 A are consistent with a helical or bilayer structure of PEO in the interlayer. TGA-DTA provides quantitative results for the hydration state of the nanocomposites, demonstrates PEO intercalation, and shows that the composites prepared from the synthetic montmorillonite are less stable than those made with SWy-1. (7)Li NMR shows that the nearest neighbor hydration state of Li(+) is unaffected by PEO intercalation and suggests weak interaction of Li(+) with PEO. (23)Na NMR shows that PEO intercalation results in the conversion of the multiple Na(+) hydration states observed for the pristine clay into inner sphere sites most likely formed through coordination with the basal oxygens of the clay. These differences between lithium and sodium suggested that tighter binding of the Na to the clay may be the origin of the conductivity of Li-montmorillonite-PEO nanocomposites being as much as 2 orders of magnitude larger than those of Na-montmorillonite-PEO nanocomposites. The results confirm the idea that polymer oxygen atoms do not participate in sequestering the exchangeable cations and agree with the jump process for cation migration advanced by Kuppa and Manias (Kuppa, V.; Manias, E. Chem. Mater. 2002, 14, 2171).
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PMID:Montmorillonite-poly(ethylene oxide) nanocomposites: interlayer alkali metal behavior. 1685 72

Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance ((29)Si MAS NMR and (13)CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.
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PMID:Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries. 2200 97

This study synthesized blended lead zirconate (PbZrO3;PZ)/poly(ethylene oxide)(PEO)/Glutinous rice starch (GRS) nanofibers by the electrospinning method. A number of parameters such as the ratio between PEO and GRS and calcination temperature have been studied. The as-spun PZ/PEO/GRS composite and PZ fibers were characterized by TG-DTA, X-ray diffraction, FT-IR and SEM, respectively. SEM results showed that smooth and continuous fibers were obtained at the volume ratio of 10:2:1, PZ/PEO/GRS. After calcination of the as-spun PZ/PEO/GRS composite nanofibers at 650 degrees C for 4 h, PZ nanofibers with perovskite structure were obtained successfully. The fibers had a uniform and smooth surface without grain boundaries. However, when the calcination temperature increased to 750 degrees C and 850 degrees C, the fiber represented a necklace-like structure with grain boundaries arranged by grain to grain unit cell clusters.
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PMID:The effect of thai glutinous rice starch on the synthesis of lead zirconate (PbZrO3) nanofibers via the electrospinning method. 2385 31

Mesoporous hollow silica nanospheres with uniform particle sizes of 31-33 nm have been successfully synthesized by cocondensation of tetramethoxysilane (TMOS) and alkyltrimethoxysilanes [RSi(OR)3], where the latter also acts as a porogen. ABC triblock copolymer micelles of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) with a core-shell-corona architecture have been employed as a soft template at pH 4. The cationic shell block with 2-vinyl pyridine groups facilitates the condensation of silica precursors under the sol-gel reaction conditions. Phenyltrimethoxysilane, octyltriethoxysilane, and octadecyltriethoxysilanes were used as porogens for generating mesopores in the shell matrix of hollow silica and the octadecyl precursor produced the largest mesopore among the different porogens, of dimension ca. 4.1 nm. The mesoporous hollow particles were thoroughly characterized by small-angle X-ray diffraction (SXRD), thermal (TG/DTA) and nitrogen sorption analyses, infra-red (FTIR) and nuclear magnetic resonance ((13)C-CP MAS NMR and (29)Si MAS NMR) spectroscopies, and transmission electron microscopy (TEM). The mesoporous hollow silica nanospheres have been investigated for drug-delivery application by an in vitro method using ibuprofen as a model drug. The hollow silica nanospheres exhibited higher storage capacity than the well-known mesoporous silica MCM-41. Propylamine functionalized hollow particles show a more sustained release pattern than their unfunctionalized counterparts, suggesting a huge potential of hollow silica nanospheres in the controlled delivery of small drug molecules.
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PMID:Synthesis of mesoporous hollow silica nanospheres using polymeric micelles as template and their application as a drug-delivery carrier. 2388 99

A pentablock copolymer of Poly(Lactide-co-Glycolide) and Pluronic F68 was synthesized using ring-opening polymerization and characterized by NMR and FTIR for confirming the structure of the block copolymer. TG-DTA studies showed PLGA:Pluronic ratio to be 4:1. As the PLGA-PEO-PPO-PEO-PLGA Pentablock Copolymer (PPPC) prepared is amphiphilic, its Critical Vesicular Concentration, was measured, which was lower at 37 degrees C than at 25 degrees C, which could provide better stability to the system at physiological temperature. The nanoparticles of PPPC vary in topographyand range from 150 to 500 nm in size, according to the synthesis route used viz Emulsion Solvent Evaporation and simple dialysis. Pentablock copolymer nanoparticles were found to entrap about 84% of hydrophobic drug, docetaxel. Drug release profile of docetaxel showed about 50% release in first 2 hours at pH 4.6 and about 80% docetaxel was released at pH 7.4, at the end of 2 days. The PPPC nanoparticles was found to be biocompatible to L929 cell lines up to 1 mg/ml concentration. Preliminary in vitro cytotoxic effect of docetaxel loaded PPPC nanoparticles against four different cancer cell lines showed 50% inhibitory concentration of 6 nM in A431 (Squamous cell carcinoma), 250 nM in HeLa (Cervical carcinoma), 800 nM in PC3 (Prostate carcinoma) and 1 microM in KB (Epidermoid carcinoma) cells.
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PMID:Biocompatible amphiphilic pentablock copolymeric nanoparticles for anti-cancer drug delivery. 2472 3