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排序方式: 共有461条查询结果,搜索用时 15 毫秒
191.
Christina M. Standfest-Hauser Thomas Lummerstorfer Roland Schmid Karl Kirchner Helmuth Hoffmann Michael Puchberger 《Monatshefte für Chemie / Chemical Monthly》2003,134(9):1167-1175
Summary. The complexes [RuCp(CH3CN)2(Ph2PCH2CH2Si(OMe)3)]PF6 and [RuCp(CH3CN) (Ph2PCH2CH2Si(OMe)3)2]PF6 were obtained in good yields by treatment of [RuCp(CH3CN)3]PF6 with 1 and 2 equivs of Ph
2PCH2CH2Si(OMe)3. Both free Ph
2PCH2CH2Si(OMe)3 and the two complexes were grafted onto the surface of powdered silica. The surface coverage was determined independently by 31P solid state NMR and IR spectroscopy. IR data revealed that for Ph
2PCH2CH2Si(OMe)3 and the complexes 52, 52, and 18 molecules, respectively, were immobilized per 100nm2 of SiO2 surface. Similar values were obtained from 31P MAS NMR measurements. With the immobilized first complex the catalytic redox isomerization of allyl alcohol to propanal has been studied by means of IR spectroscopy and 1H NMR spectroscopy showing the quantitative formation of aldehyde. While in the first cycle satisfactory turnover numbers were achieved, the subsequent cycles showed only low conversions to aldehyde presumably due to decomposition of the complex. The immobilized second complex was catalytically inactive.Received February 25, 2003; accepted March 24, 2003
Published online August 18, 2003 相似文献
192.
T. Nedelčev I. Krupa D. Lath M. Špírková 《Journal of Sol-Gel Science and Technology》2008,46(1):47-56
Rhodamine B (RB), Naphthol Blue Black (NBB), Metanil Yellow (MTY) and Bismarck Brown R (BHR) immobilized within a modified silica sol were used for the surface dyeing of textiles, namely polyester and viscose
fabrics. Silica sols were characterized by FTIR and dynamic light-scattering measurements. The sol was dip-coated onto the
fabrics and deposits were formed. Three similar procedures for the formation of silica deposits, using tetraethoxysilane (TEOS)
and (3-glycidoxypropyl)trimethoxysilane (GPTMS) as precursors in acidified ethanol, were tested. Interactions between dyes
and silica precursors were investigated by FTIR measurements. Leaching was detected and quantified by UV–Vis measurements
on the composition of washing solutions. Incorporation of GPTMS into silica sols reduces dye leaching from the silica deposits. 相似文献
193.
The imperative role of functionalized natural alginate in immobilization of Lactobacillus delbrucekii (NCIM 2365) cells in production of optically pure L (+) lactic acid was studied. L. delbrucekii cells were immobilized in alginate, succinylated alginate and carrageenan to evaluate the bead stability and selectivity towards production of optically pure L (+) lactic acid. The scanning electron microscopic studies of free and immobilized cells show little morphological changes. The present study highlights the use of functionalized alginate-immobilized L. delbrucekii cells in production of L (+) lactic acid in higher yields (0.93 Yp/s in grams) with an improved enantioselectivity (99%). In addition, they further revealed decreased by-product formation (acetic and propionic acid) when compared to free and other immobilized cell fermentation. 相似文献
194.
Subba Rao Ch Madhavendra SS Sreenivas Rao R Hobbs PJ Prakasham RS 《Applied biochemistry and biotechnology》2008,150(1):65-83
This study uses an overall evaluation criterion for improving the immobilized bead reusability and extracellular enzyme production by immobilized cells by assigning relative weightage to bead reusability, enzyme production, and cell leakage. Initially, alkaline protease production by alginate-immobilized Bacillus circulans (MTCC 6811) was analyzed using L18 orthogonal array (OA). The resultant optimized parameters were further fine-tuned with L9 OA experimentation. At L18-OA analysis, inoculum level and CaCl(2) had least influence at individual level. At the interactive level, incubation time revealed maximum and minimum interaction with sodium alginate and glucose concentration, respectively. L9 experimentation indicated that glucose concentration contributed the major influence on protease production followed by matrix material and incubation time at the individual level, and at the interactive level, matrix concentration played a vital role by interacting with incubation time, inoculum, and CaCl(2) concentration. All selected input parameters showed significance either at individual level or interactive in both OAs. Scanning electron microscopy analysis showed bacterial morphology variation with variation of matrix concentration. Overall, glucose concentration depicted a major influence at the individual level for the enzyme production. Significant improvement, approximately 147%, in enzyme yield was observed. Economic enzyme production by immobilized B. circulans is regulated by interactive influence of fermentation parameters, which influence the immobilized bead stability, reusability, and enzyme yield. 相似文献
195.
β-Glucosidase is a key enzyme in the hydrolysis of cellulose for producing feedstock glucose for various industrial processes.
Reuse of enzyme through immobilization can significantly improve the economic characteristics of the process. Immobilization
of the fungal β-glucosidase by covalent binding and physical adsorption on silica gel and kaolin was conducted for consequent
application of these procedures in large-scale industrial processes. Different immobilization parameters (incubation time,
ionic strength, pH, enzyme/support ratio, glutaric aldehyde concentration, etc.) were evaluated for their effect on the thermal
stability of the immobilized enzyme. It was shown that the immobilized enzyme activity is stable at 50 °C over 8 days. It
has also been shown that in the case of immobilization on kaolin, approximately 95% of the initial enzyme was immobilized
onto support, and loss of activity was not observed. However, covalent binding of the enzyme to silica gel brings significant
loss of enzyme activity, and only 35% of activity was preserved. In the case of physical adsorption on kaolin, gradual desorption
of enzyme takes place. To prevent this process, we have carried out chemical modification of the protein. As a result, after
repeated washings, enzyme desorption from kaolin has been reduced from 75 to 20–25% loss. 相似文献
196.
Dorota Duraczynska Ewa M. Serwicka Alicja Drelinkiewicz 《Journal of organometallic chemistry》2008,693(3):510-518
The cationic ruthenium(II) complex [(η5-MeC5H4)Ru(η3-PPh2CHCH2)(η1-PPh2CHCH2)]+ (1) containing the hemilabile phosphaallyl ligand in two different coordination modes has been immobilized inside the pores of aluminated hexagonal mesoporous silica HMS(Si/Al = 40) by direct ion exchange method. This material was characterized by X-ray diffraction, thermogravimetric analysis, FTIR, solid state NMR (29Si, 27Al), UV-Vis, and X-ray photoelectron spectroscopies. The textural properties were determined from nitrogen adsorption at 77 K. (1)/HMS(Si/Al = 40) was shown to be active and selective in the catalytic hydrogenation of phenylacetylene. 相似文献
197.
This paper reports a novel piezoelectric quartz crystal immnuosensor based on hyperbranched polymer films for the detection of α-Fetoprotein. In this strategy, the sensing interfaces consist of a primary cystamine monolayer assembled onto Au electrodes associated with the piezoelectric quartz crystal. The monolayer is further modified with a new hyperbranched polymer which was synthesized through direct polycondensation of monomer 5-[3-(4-aminophenyl) propionylamino] isophthalic acid. The detection performances of resulting immunosensor were investigated by use of the antibody-antigen model system of α-Fetoprotein (AFP), an important indicator in the diagnosis of clinical cancers. The analytical technique is characterised through the investigation of different methods of assembling the monolayers used as supports, as well as by comparing two different types of supports. It was found that the developed sensing interface could perform more effectively in antibody-antigen binding and consequently increased the sensitivity of the whole piezoelectric immunosensor. Moreover, the method should also be useful for the construction of other kind of immunosensors. 相似文献
198.
A new method for the determination of lactic acid based on the immobilization enzyme fluorescence capillary analysis (IE-FCA) was proposed. Lactic dehydrogenase (LDH) was immobilized on inner surface of a capillary with glutaraldehyde, and an immobilized enzyme lactate capillary bioreactor (IE-LCBR) was formed for the determination of lactic acid. After nicotinamide adenine dinucleotide (NAD+) is mixed with lactic acid solution, it was sucked into the IE-LCBR and was detected at λex 353 nm/λem 466 nm. Optimized conditions are as follows: the temperature is 38 °C; the reaction time is 15 min; the concentrations of Tris buffer (pH 8.8) and NAD+ are 0.1 mol L−1 and 4 mmol L−1, respectively; the concentration of LDH used for immobilization is 15 kU L−1. The concentration of lactic acid is directly proportional to the fluorescence intensity measured from 0.50 to 2.0 mmol L−1; and the analytical recovery of added lactic acid was 99–105%. The minimum detection limit of the method is 0.40 mmol L−1 and sensitivity of the IE-CBR is 4.6 F mmol−1 L−1 lactate. Its relative standard deviation (R.S.D.) is ≤2.0%. This IE-FCA method was employed for determination of lactate in milk drink. 相似文献
199.
A new antibody immobilization strategy was proposed for the fabrication of a label-free capacitive immunosensor based on electrodeposition of nanometer-sized bioactive hydroxyapatite (HAP). By a procedure of constant current cathodal electrodeposition, a nano-HAP film with bioactivity was formed on a self-assembled β-mercaptoethanol monolayer-modified gold electrode. A suitable amount of chitosan was added into the electrodeposition solution with the aim of obtaining a strong and homogeneous HAP-coating film. After blocking with long-chain alkylthiol and then embedding antibody by coupling with divinylsulphone, the electrode was possessed of a higher initial capacitance value, which was suitable for capacitive transduction. The sensitive layer was characterized by Fourier transform infrared spectrum, scanning electron microscopy and electrochemical method. Human transferrin immunoassay was selected as the testing system. The linear response range of the sensor for transferrin was between 1 and 100 ng/mL with a detection limit of 0.15 ng/mL. After simply rinsing with subacidity solution, the regenerated sensor achieved up to 10 assay cycles without significant loss of sensitivity. 相似文献
200.
High-performance monolithic disk affinity chromatography was applied to the investigation of formation of complexes between (1) complementary polyriboadenylic and polyribouridylic acids, e.g. poly(A) and poly(U), respectively, (2) poly(A) and synthetic polycation poly(allylamine), pAA. Polyriboadenylic acid and poly(allylamine) were immobilized on macroporous disks (CIM disks). Quantitative parameters of affinity interactions between macromolecules were established using frontal analysis at different flow rates. 相似文献