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91.
H. Polli L. A. M. Pontes A. S. Araujo Joana M. F. Barros V. J. FernandesJr. 《Journal of Thermal Analysis and Calorimetry》2009,95(1):131-134
The degradation kinetics of the ABS terpolymer (acrylonitrile-butadiene-styrene) was investigated by means of thermogravimetric
analysis. The samples were heated from 30 to 900°C in nitrogen atmosphere applying three different heating rates: 5, 10 and
20°C min−1. The Vyazovkin model-free kinetic method was used to calculate the activation energy (E) of the degradation process as a function of conversion and temperature. Between 20 and 80% of conversion, E was calculated
and the figures were: for ABS GP, E is 204.5±11.5 kJ mol−1 (medium value); for ABS HI, E is 239.0±9.8 kJ mol−1; for ABS HH, E is 242.4±5.4 kJ mol−1. 相似文献
92.
Yan Lee Dr. Takehiko Ishii Dr. Horacio Cabral Dr. Hyun Jin Kim Ji‐Hun Seo Nobuhiro Nishiyama Dr. Hiroki Oshima Kensuke Osada Dr. Kazunori Kataoka Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(29):5309-5312
Special delivery! Polyionic complex (PIC) micelles that contain the charge‐conversional moieties citaconic amide or cis‐aconitic amide were developed for cytoplasmic protein delivery. The increase of the charge density on the protein cargo helped the stability of the PIC micelles without cross‐linking, and the charge‐conversion in endosomes induced the dissociation of the PIC micelles to result in efficient endosomal release (see picture).
93.
94.
Sousa J Alves G Abrantes J Fortuna A Falcão A 《Analytical and bioanalytical chemistry》2012,403(1):93-129
Fluoroquinolones are one of the most promising and intensively studied drugs of contemporary anti-infective chemotherapy.
New fluoroquinolone antibacterials with improved pharmacokinetic properties and a broad spectrum of activity have been developed,
opening new windows of opportunity for clinical use. To our knowledge, no comprehensive and critical review of the analytical
methods for the determination of these agents, which correspond to the third- and fourth-generation quinolones, has yet been
published. This work summarizes for the first time most of the liquid chromatographic methods reported in the literature for
the separation and quantification of the new fluoroquinolones in biological matrices and pharmaceutical formulations. A systematic
and detailed survey of physicochemical properties, sample preparation procedures, and chromatographic and detection conditions
is presented herein. In the course of this review several liquid chromatographic methods are discussed: reversed-phase high-performance
liquid chromatography (RP-HPLC), ion-exchange high-performance liquid chromatography (IEX-HPLC), hydrophilic interaction liquid
chromatography (HILIC), high-performance thin-layer chromatography (HPTLC) and other chiral chromatographic methods. Their
advantages, applicability and limitations are also examined. 相似文献
95.
Martins PT Velazquez-Campoy A Vaz WL Cardoso RM Valério J Moreno MJ 《Journal of the American Chemical Society》2012,134(9):4184-4195
Passive transport across cell membranes is the major route for the permeation of xenobiotics through tight endothelia such as the blood–brain barrier. The rate of passive permeation through lipid bilayers for a given drug is therefore a critical step in the prediction of its pharmacodynamics. We describe a detailed study on the kinetics and thermodynamics for the interaction of chlorpromazine (CPZ), an antipsychotic drug used in the treatment of schizophrenia, with neutral and negatively charged lipid bilayers. Isothermal titration calorimetry was used to study the partition and translocation of CPZ in lipid membranes composed of pure POPC, POPC:POPS (9:1), and POPC:Chol:POPS (6:3:1). The membrane charge due to the presence of POPS as well as the additional charge resulting from the introduction of CPZ in the membrane were taken into account, allowing the calculation of the intrinsic partition coefficients (K(P)) and the enthalpy change (ΔH) associated with the process. The enthalpy change upon partition to all lipid bilayers studied is negative, but a significant entropy contribution was also observed for partition to the neutral membrane. Because of the positive charge of CPZ, the presence of negatively charged lipids in the bilayer increases both the observed amount of CPZ that partitions to the membrane (KP(obs)) and the magnitude of ΔH. However, when the electrostatic effects are discounted, the intrinsic partition coefficient was smaller, indicating that the hydrophobic contribution was less significant for the negatively charged membrane. The presence of cholesterol strongly decreases the affinity of CPZ for the bilayer in terms of both the amount of CPZ that associates with the membrane and the interaction enthalpy. A quantitative characterization of the rate of CPZ translocation through membranes composed of pure POPC and POPC:POPS (9:1) was also performed using an innovative methodology developed in this work based on the kinetics of the heat evolved due to the interaction of CPZ with the membranes. 相似文献
96.
Pereira-Netto AB Meneguin RG Biz A Silveira JL 《Applied biochemistry and biotechnology》2012,166(1):197-207
Agar is a complex mixture of gel-forming polysaccharides. Gelling agents are very often used to provide proper support for
plants grown in semisolid culture media. And agar is the most frequently used gelling agent in plant tissue culture media.
Galactomannans, another group of gel-forming polysaccharides, consists of a (1 → 4)-linked β-d-mannopyranosyl backbone partially substituted at O-6 with d-galactopyranosyl side groups. In this work, we demonstrate that a statistically significant 2.7-fold increase on the multiplication
rate (MR) for in vitro-grown Marubakaido (Malus prunifolia) shoots was associated with a 12.5% replacement of agar in the semi-solid culture media for a galactomannan obtained from
seeds of Schizolobium paraybae. This increase on MR was due mainly to a 1.9-fold increase in the number of main branches and an 8.6-fold increase in the
number of primary lateral branches. Gas liquid chromatography and thin layer chromatography analyzes demonstrated that the
galactomannan-driven enhancement of the in vitro multiplication rate of the Marubakaido apple rootstock was not related to
the galactomannan degradation. To the best of our knowledge, this is the first report on the successful use of partial replacement
of high quality agar by a galactomannan from S. paraybae in a micropropagation system for a tree species. 相似文献
97.
Ramos CI Santana-Marques MG Ferrer-Correia AJ Barata JF Tomé AC Neves MG Cavaleiro JA Abreu PE Pereira MM Pais AA 《Journal of mass spectrometry : JMS》2012,47(4):516-522
Two new isomeric aminomethyl corrole derivatives of [5,10,15-tris(pentafluorophenyl)corrolato]gallium(III) were synthesized with pyridine (py) molecules as axial ligands. When investigated by electrospray ionization mass spectrometry, in the positive and the negative ion modes, these compounds showed an unusual gas-phase behavior that could be used for their differentiation. In the positive ion mode, the differentiation was achieved through the formation of diagnostic fragment ions formed from [M-py?+?H](+) precursors, by (CH(3) )(2) NH and HF losses. An unusual addition of water to the main fragment ions provides an alternative route for isomer identification. Semi-empirical calculations were performed to elucidate the structures and stabilities of the main ionic species formed in the positive ion mode. In the negative ion mode isomer discrimination is accomplished via the fragmentation of the methoxide adduct ions [M-py?+?CH(3) O](-) through (CH(3) )(2) N(.) and HF losses. 相似文献
98.
Maria M. Milanova Petya G. Kovacheva Radina P. Kralchevska Jovo R. Kolev Joana Ts. Zaharieva Dimitar S. Todorovsky 《Central European Journal of Chemistry》2012,10(6):1850-1858
Microcomposites consisting of TiO2 and ThF4 or UO3 (0.5?C2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of the respective additives. X-ray diffraction study reveals small effect of the latter on TiO2 phase composition and cell parameters and significant influence on the crystallite size and UV/Vis reflectance spectra. The photocatalytic tests in presence of TiO2-ThF4 microcomposites under UV and solar irradiation show a non-monotonic increase of the Malachite Green degradation rate constant with the increase of ThF4-content. No changes in the photocatalytic activity are observed in the presence of UO3 but the latter composites exhibit activity in darkness. The results are compared with previously reported data on the performance of TiO2-ThO2 photocatalyst with the same radioactivity and suggest that both radioactivity and the chemical nature of the dopants are responsible for the photocatalytic performance of TiO2-based composites containing radioactive substances. 相似文献
99.
Sara C.A. Sousa Joana R. Bernardo Carlos C. Romão Ana C. Fernandes 《Tetrahedron》2012,68(39):8194-8197
This work reports a novel method for the deoxygenation of aromatic and aliphatic sulfoxides catalyzed by oxo-rhenium complexes without adding any reducing agent. The oxo-rhenium complex ReOCl3(PPh3)2 proved to be very efficient for the deoxygenation of several sulfoxides with tolerance of different functional groups. 相似文献
100.
Joana Monterrosa José Daniel Martínez Mary Lorena Araujo Felipe Brito Giuseppe Lubes Mildred Rodríguez Lino Hernández Vito Lubes 《Journal of solution chemistry》2012,41(4):589-598
We studied speciation of the mixed-ligand complex formation equilibria of vanadium(III) with both 2,2??-bipyridine (Bipy) and the amino acids glycine (HGly), proline (HPro), ??-alanine (H??Ala), and ??-alanine (H??Ala) by means of electromotive forces measurements emf(H) using 3.0?mol?dm?3 KCl as the ionic medium at 25 °C. The experimental data were analyzed by means of the computational least-squares program LETAGROP, taking into account the hydrolysis of the vanadium(III) cation, the respective stability constants of the binary complexes, and the acid/base reactions of the ligands which were kept fixed during the analysis. In all four amino acid systems studied we observed the complexes [V2O(Bipy)(B)]3+, [V2O(Bipy)2(B)2]2+, [V(OH)(Bipy)(B)2] and [V(OH)2(Bipy)(B)], where B represents the deprotonated form of the amino acids studied in this work. The respective stability constants were determined and the species distribution diagrams as a function of pH are briefly discussed. 相似文献