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51.
Poly(ethylene glycol)(PEG)‐based interpenetrating polymeric network (IPN) hydrogels were prepared for the application of enzyme immobilization. Poly(acrylamide)(PAAm) was chosen as the other network of IPN hydrogel and different concentration of PAAm networks were incorporated inside the PEG hydrogel to improve the mechanical strength and provide functional groups that covalently bind the enzyme. Formation of IPN hydrogels was confirmed by observing the weight per cent gain of hydrogel after incorporation of PAAm network and by attenuated total reflectance/Fourier transform infrared (ATR/FTIR) analysis. Synthesis of IPN hydrogels with higher PAAm content produced more crosslinked hydrogels with lower water content (WC), smaller Mc and mesh size, which resulted in enhanced mechanical properties compared to the PEG hydrogel. The IPN hydrogels exhibited tensile strength between 0.2 and 1.2 MPa while retaining high levels of hydration (70–81% water). For enzyme immobilization, glucose oxidase (GOX) was immobilized to PEG and IPN hydrogel beads. Enzyme activity studies revealed that although all the hydrogels initially had similar enzymatic activity, enzyme‐immobilizing PEG hydrogels lost most of the enzymatic activity within 2 days due to enzyme leaching while IPN hydrogels maintained a maximum 80% of the initial enzymatic activity over a week due to the covalent linkage between the enzyme and amine groups of PAAm. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
52.
Pihlström T Blomkvist G Friman P Pagard U Osterdahl BG 《Analytical and bioanalytical chemistry》2007,389(6):1773-1789
A multiresidue method based on extraction with ethyl acetate has been used at the Swedish National Food Administration since
1989 to monitor pesticide residues in fruit and vegetables. The method has been continuously adjusted, resulting in simple
and quick analyses of pesticide residues. To recover basic pesticides, the addition of an alkali is necessary. The addition
of sodium hydrogen carbonate has been shown to recover all pesticides effectively without any degradation. The liquid chromatography
(LC) with tandem mass spectrometry (MS/MS) technique has made it possible to analyse more polar pesticides and to replace
many single methods. The latest development in the multiresidue method, comprising the use of gas chromatography (GC) with
MS/MS, has further improved the analysis by replacing the conventional GC detectors. The need for cleanup has been reduced
or eliminated entirely. Consequently, the method has been simplified in a way that makes it possible to recover all included
analytes in many different matrices in one single extraction and to detect them either with GC-MS/MS or with LC-MS/MS. 相似文献
53.
Anna A. Rugal Vladimir M. Gun’ko Valentina N. Barvinchenko Vladimir V. Turov Tatyana V. Semeshkina Vladimir I. Zarko 《Central European Journal of Chemistry》2007,5(1):32-54
Interaction of human plasma fibrinogen (HPF) with fumed nanosilica A-300 in a phosphate buffer solution (PBS) was studied
using 1H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial water in the temperature range of 210–273 K, TSDC
(90 < T < 265 K), adsorption, FTIR, and UV spectroscopy methods. An increase in concentration of HPF in the PBS leads to a decrease
in amounts of structured water (frozen at T < 273 K) because of coagulation of HPF molecules. Addition of nanosilica to the HPF solution strongly reduces the amounts
of structured water because of adsorption interaction of HPF molecules with silica nanoparticles, self-association of HPF
molecules, formation of denser packed hybrid agglomerates with HPF and silica, and lastly, because of conformational changes
of HPF. A monolayer adsorption capacity of A-300 corresponds to 156 mg of HPF per gram of silica. The FTIR and UV spectra
show that the HPF adsorption on silica leads to structural changes of the protein molecules. These changes and formation of
hybrid HPF/A-300 aggregates can increase the rate of clotting that is of importance on nanosilica application as a component
of tourniquet preparations.
相似文献
54.
Behaviour of pure water and water mixture with benzene or chloroform adsorbed onto ordered mesoporous silicas 总被引:1,自引:0,他引:1
Vladimir M. Gun’ko Vladimir V. Turov Alexander V. Turov Vladimir I. Zarko Vasiliy I. Gerda Victor V. Yanishpolskii Inna S. Berezovska Valentin A. Tertykh 《Central European Journal of Chemistry》2007,5(2):420-454
Structural characteristics of synthesized ordered mesoporous silicas MCM-41, MCM-48 and SBA-15 were studied using XRD, nitrogen
adsorption and FTIR methods. Pure water and mixtures with water/benzene and water/chloroform-d adsorbed onto silicas were studied by 1H NMR spectroscopy with layer-by-layer freezing-out of bulk and interfacial liquids. Concentrated aqueous suspensions of MCM-48
and SBA-15 were studied by thermally stimulated depolarization current (TSDC) method. Benzene and chloroform-d can displace a portion of water to broad pores from the pore walls and from narrower pores, especially in the case of a large
excess of an organic solvent. This process is accompanied by diminution of both interaction energy of water with an adsorbent
surface and freezing temperature depression of adsorbed water. The effect of nonpolar benzene on pore water is much stronger
than that of weakly polar chloroform-d. Modifications of the Gibbs-Thomson relation to describe the freezing point depression of mixtures of immiscible liquids
confined in pores allow us to determine distribution functions of sizes of structures with unfrozen pore water and benzene.
Former address: Pisarzhevskii Institute of Physical Chemistry, 31 Prospect Nauki, Kiev, Ukraine 相似文献
55.
Young Gun Ko Ung Su Choi Tai Young Kim Dong June Ahn Yong Jin Chun 《Macromolecular rapid communications》2002,23(9):535-539
A new chelating fiber, poly(acrylo‐amidino diethylenediamine), was synthesized based on polyacrylonitrile fibers in diethylenetriamine with the aid of AlCl3. Complex formation with CrO42– was strongly pH‐dependent, as complexes formed only in the presence of NH3+ and NH2+. In the medium pH region, both ionic and hydrogen bonds were formed between poly(acrylo‐amidino diethylenediamine) and the chromate ion, as was confirmed by means of FT‐IR spectroscopy. 相似文献
56.
Jongchul Seo Jongho Jeon Yong Gun Shul Haksoo Han 《Journal of Polymer Science.Polymer Physics》2000,38(21):2714-2720
The water sorption behavior and the activation energy were investigated for various chemical structure polyimide thin films; BPDA‐PDA, BPDA‐ODA, PMDA‐ODA, and 6FDA‐ODA. The activation energy for the water diffusion varied in the range of 5.53 to 9.27kcal/mol, and was in the increasing order: BPDA‐PDA < BPDA‐ODA < PMDA‐ODA < 6FDA‐ODA. BPDA‐PDA and BPDA‐ODA polyimide films showed relatively well‐ordered morphological structure, which results in relatively low diffusion coefficient and high activation energy. It was found that the diffusion coefficient and the activation energy are significantly related to the in‐plane orientation, crystallinity, and packing order in the polyimide thin films. The morphological structure was predominant factors for the water diffusion coefficient and activation energy in the polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2714–2720, 2000 相似文献
57.
Young Gun Ko Ung Su Choi Byeng Gil Ahn Dong June Ahn 《Journal of polymer science. Part A, Polymer chemistry》2000,38(15):2815-2823
High‐performance materials for flameproofing, phosphates (polyphosphate and ammonium phosphate) were synthesized on viscose rayon felt. This surface reaction has the advantage of a nonblooming effect and an application in thermosetting plastics. Metal complexes have the effect of reducing the amount of smoke. Therefore, in the second step, transition‐metal complexes were synthesized on the viscose rayon ammonium phosphate felt. This article focuses on the surface modification of phosphates and metal complexes on viscose rayon. All reactions were confirmed by attenuated total reflectance Fourier transform infrared and time‐of‐flight secondary ion mass spectrometry. As the concentrations of phosphoric acid and urea increased, the peak intensities of ammonium ion groups and phosphate groups greatly increased. The thermal properties of the synthesized materials were studied with thermogravimetric analysis and oxygen index testing. On the basis of the experimental results, the synthesized flame‐retardancy materials showed excellent physicochemical and thermal effects and flame retardancy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2815–2823, 2000 相似文献
58.
59.
Soo‐Gyun Roh Ki‐Min Park Gil‐Jae Park Shigeru Sakamoto Kentaro Yamaguchi Kimoon Kim 《Angewandte Chemie (International ed. in English)》1999,38(5):637-641
Like with a string of pearls , four molecular “beads” are threaded on a molecular rectangle to form a molecular necklace. This rectangular species is synthesized from two L‐shaped, preorganized pseudorotaxanes with two molecular beads each (cucurbituril, schematically symbolized by the barrels), held together by Cu2+ ions [Eq. (1)]. 相似文献
60.
The wide tuning characteristics of double-ring coupled lasers with/without an extended waveguide are analyzed and optimized using the scattering matrix formalism. To obtain the optimum design schemes of the tunable laser diodes, the cross coupling ratios of two rings, the tuning enhancement factor, the propagation loss of passive waveguides, the optical gain of an active region, and the back and front-facet reflectivity of the waveguide are taken into account. When the coupling ratio of the ring and input/output waveguides is fixed, the extinction ratio and the linewidth are decreased as the tuning enhancement factor is increased, while the tuning range is increased. 相似文献