排序方式: 共有68条查询结果,搜索用时 15 毫秒
61.
Elmas B Tuncel M Senel S Patir S Tuncel A 《Journal of colloid and interface science》2007,313(1):174-183
N-isopropylacrylamide (NIPA) based uniform thermosensitive microgels were synthesized by dispersion polymerization by using relatively hydrophilic crosslinking agents with hydroxyl functionality. Glycerol dimethacrylate (GDMA), pentaerythritol triacrylate (PETA) and pentaerythritol propoxylate triacrylate (PEPTA) were used as crosslinking agents with different hydrophilicities. A protocol was first proposed to determine the crosslinking density distribution in the thermosensitive microgel particles by confocal laser scanning microscopy (CLSM). The microgels were fluorescently labeled by using hydroxyl group of the crosslinking agent. The CLSM observations performed with the microgels synthesized by three different crosslinking agents showed that the crosslinking density exhibited a quadratic decrease with the increasing radial distance in the spherical microgel particles. This structure led to the formation of more loose gel structure on the particle surface with respect to the center. Then the use of hydrophilic crosslinking agents in the dispersion polymerization of NIPA made possible the synthesis of thermosensitive microgels carrying long, flexible and chemically derivatizable (i.e., hydroxyl functionalized) fringes on the surface by a single-stage dispersion polymerization. The microgels with all crosslinking agents exhibited volume phase transition with the increasing temperature. The microgel obtained by the most hydrophilic crosslinking agent, GDMA exhibited higher hydrodynamic diameters in the fully swollen form at low temperatures than those obtained by PETA and PEPTA. Higher hydrodynamic size decrease from fully swollen form to the fully shrunken form was also observed with the same microgel. 相似文献
62.
63.
Durmaz YY Karagoz B Bicak N Demirkol DO Yalcinkaya EE Timur S Yagci Y 《Macromolecular bioscience》2011,11(1):141-150
Hydrophobic- and/or hydrophilic-polymer-grafted PDVB microspheres are synthesized by the combination of hydrobromination and click-chemistry processes. The modified-PDVB microspheres and the intermediates at various stages of synthesis are characterized using GPC, 1H NMR and FTIR spectroscopy and TGA analysis. Use of the microspheres as a support matrix for reversible protein immobilization via adsorption is investigated. The system parameters such as the adsorption conditions (i.e., enzyme concentration, medium pH) and desorption are studied and evaluated with regards to the biocatalytic activity and adsorption capacity. 相似文献
64.
Two new, sensitive and selective spectrofluorimetric methods have been developed for the determination of gemifloxacin (GFX)
in tablets and spiked plasma samples. Gemifloxacin, as a primary amine compound, reacts with 7-chloro-4-nitrobenzofurazon
(NBD-Cl) (for method A) and fluorescamine (for method B) which are a highly sensitive fluorogenic reagents used in many investigations.
For method A, the reaction product was measured spectrofluorimetrically at 516 nm with excitation at 451 nm. The reaction
proceeded quantitatively at pH 8.5, 80 °C in 7 min. For method B, the method was based on the reaction between GFX and fluorescamine
in borate buffer solution of pH 8.5 to give highly fluorescent derivatives that were measured at 481 nm using an excitation
wavelength of 351 nm. The fluorescence intensity was directly proportional to the concentration over the range 40–200 ng mL−1 and 100–1,200 ng mL−1 for method A and B, respectively. Successful applications of the developed methods, for the drug determination in pharmaceutical
preparations and spiked plasma samples, were performed. 相似文献
65.
Altıntas EB Türkmen D Karakoç V Denizli A 《Colloids and surfaces. B, Biointerfaces》2011,85(2):323-240
Metal-chelating affinity beads have attracted increasing interest in recent years for protein purification. In this study, iminodiacetic acid (IDA) was covalently attached to the poly(glycidyl methacrylate) [PGMA] beads (1.6 μm in diameter). Cu(2+) ions were chelated via IDA groups on PGMA beads for affinity binding of hemoglobin (Hb) from human blood hemolysate. The PGMA beads were characterized by scanning electron microscopy (SEM). The PGMA-Cu(2+) beads (628 μmol/g) were used in the Hb binding-elution studies. The effects of Hb concentration, pH and temperature on the binding efficiency of PGMA-Cu(2+) beads were performed in a batch system. Non-specific binding of Hb to PGMA beads in the absence of Cu(2+) ions was very low (0.39 mg/g). The maximum Hb binding was 130.3 mg/g. The equilibrium Hb binding increased with increasing temperature. The negative change in Gibbs free energy (ΔG°<0) indicated that the binding of Hb on the PGMA-Cu(2+) beads was a thermodynamically favorable process. The ΔS and ΔH values were 102.2 J/mol K and -2.02 kJ/mol, respectively. Significant amount of the bound Hb (up to 95.8%) was eluted in the elution medium containing 1.0 M NaCl in 1 h. The binding followed Langmuir isotherm model with monolayer binding capacity of 80.3-135.7 mg/g. Consecutive binding-elution experiments showed that the PGMA-Cu(2+) beads can be reused almost without any loss in the Hb binding capacity. To test the efficiency of Hb depletion from blood hemolysate, eluted portion was analyzed by fast protein liquid chromatography. The depletion efficiency for Hb was above 97.5%. This study determined that the PGMA-Cu(2+) beads had a superior binding capacity for Hb compared to the other carriers within this study. 相似文献
66.
Decolorization Potential of Some Reactive Dyes with Crude Laccase and Laccase-Mediated System 总被引:2,自引:0,他引:2
Samet Şaşmaz Serap Gedikli Pınar Aytar Gökhan Güngörmedi Ahmet Çabuk Evrim Hür Arzu Ünal Nazif Kolankaya 《Applied biochemistry and biotechnology》2011,163(3):346-361
In this study, decolorization of dyestuffs, such as Reactive Red 198, Rem Blue RR, Dylon Navy 17, Rem Red RR, and Rem Yellow
RR was studied using laccase and laccase-mediated system. The laccases are known to have an important potential for remediation
of pollutants. Among these dyestuffs, decolorization of Rem Blue RR and Dylon Navy 17 was performed with crude laccase under
optimized conditions. Vanillin was selected as laccase mediator after screening six different compounds with Rem Yellow RR,
Reactive Red 198, and Rem Red RR as substrates. However, Rem Yellow RR was not decolorized by either laccase or laccase-mediated
system. It is observed that the culture supernatant contained high laccase activity after treatment with catalase that was
responsible for the decolorization. Besides, culture supernatant with high laccase activity as enzyme source was treated with
catalase; in this way, the hypothesis that laccase was the enzyme responsible for decolorization was supported. The Rem Blue
RR was decolorized with 64.84% under the optimum conditions and Dylon Navy 17 with 75.43% with crude laccase. However, using
the laccase and vanillin, the decolorization of Reactive Red 198 and Rem Red RR was found to be 62% and 68%, respectively.
Our study demonstrated that the decolorization abilities of laccase and/or laccase mediator systems were based on the types
of mediator, the dye structure, and the standard experimental conditions. Also, the electrochemical behaviors of some samples
were studied. The redox potentials of these samples were determined using cyclic voltammetry on glassy carbon electrode in
phosphate buffer (pH 6) solution. 相似文献
67.
Deniz Hür Sultan Funda Ekti Dal Evrim Hür 《Journal of organometallic chemistry》2011,696(13):2543-2548
In this study, crystalline and chirally stable carboxyl-protected and novel unprotected N-ferrocenoyl amino acid derivatives of Ser, Cys, Ala, Phe, Trp, Asp and Asn have been prepared. These amino acids undergo substitution reaction with 1-(ferrocenylcarbonyl)-1H-benzotriazole, 1, in partially aqueous media under microwave irradiation. 相似文献
68.
F. Senel Boydag Shaval V. Mamedov Vilayet A. Alekperov Gulcin Kandemir 《Macromolecular Symposia》1999,146(1):187-192
The optical clarity of the polymeric material can be influenced by changing the preparations parameters and thus the polymer structure. In this study, the transmittance, absorptance and reflectance of the polypropylene (PP) based polymer composites, synthesized by pressing method, changing the thickness between 8 — 29 μm, are investigated. Infrared and ultraviolet spectra of PP/diamond and PP/fiber composite in the wavelength range 200–25000 nm are examined. Optical absorption spectra recorded in the UV-Visible range are presented; the determined values of energy gaps are listed. The results indicate that both mechanism, direct and indirect transitions may exist. The analysis of absorption peaks corresponding to oxygen groups, for PP/diamond (0.3–0.5 %) and PP/fiber (20–30 %) composites, show low optical densities which complies with our other studies. 相似文献