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排序方式: 共有96条查询结果,搜索用时 31 毫秒
31.
Alessandra BassoLuigi De Martin Cynthia EbertPaolo Linda Lucia Gardossi Rein V. Ulijn Sabine L. Flitsch 《Tetrahedron letters》2003,44(32):6083-6085
Organically modified xerogels (OMXNH2) can be used as an easy to handle and chemically stable support in solid-phase chemistry and are compatible with enzymatic transformations. 相似文献
32.
Báez-Vásquez MA Adrio JL Piret JM Demain AL 《Applied biochemistry and biotechnology》1999,81(3):145-152
Resting cells of Streptomyces clavuligerus NP-1, which posses deacetoxy-cephalosporin C synthase activity, have been shown previously to perform oxidative ring expansion
of penicillin G in the presence of iron, ascorbic acid, and α-ketoglutaric acid to form deacetoxycephalosporin G. Further
studies on this bioconversion indicated that use of MOPS or HEPES buffer at pH 6.5 more than doubled the extent of the reaction
observed with the previously used Tris-HCl at pH 7.4. Levels of bioconversion as high as 16.5% were achieved at low penicillin
G concentrations. Previously, conversion yields were <1%. 相似文献
33.
Penicillin acylase ofE. coli NCIM 2400 has been purified to homogeneity using a combination of hydrophobic interaction chromatography and DEAE-cellulose
treatment. A variety of substituted matrices were synthesized using D- or DL-phenylglycine, norleucine, ampicillin, or amoxycillin
as ligands, all of which retained penicillin acylase at high concentrations of ammonium sulfate or sodium sulfate. The enzyme
could be eluted nonbiospecifically by buffer of lower ionic strength with over 95% recovery of the activity. Ammonium chloride,
ammonium nitrate, sodium chloride, sodium nitrate, and potassium chloride were ineffective in either adsorption or elution
of the enzyme on these columns. Further purification of this partially pure enzyme with DEAE-cellulose at pH 7.0–7.2 yielded
an enzyme preparation of very high purity according to electrophoretic and ultracentrifugal analyses, its specific activity
being as high as 37 U/mg protein. The purifiedf enzyme has a molecular weight of 67,000 a sedimentation coefficient of 4.0S,
and resolves into two forms upon isoelectric focusing. Overall recoveries ranged between 75 and 85%. Ease of operation, high
recoveries, high purity of the enzyme and prolonged reuse of the conjugates make the process economically feasible and possibly
of great commercial importance. 相似文献
34.
酶法拆分D,L-苯丙氨酸制备D-苯丙氨酸 总被引:7,自引:0,他引:7
在固定化青霉素酰化酶(IPA-750)存在下,通过N-苯乙酰-D,L-苯丙氨酸(2)的选择性水解完成了酶法拆分D,L-苯丙氨酸(1)制备D-苯丙氨酸(5)的过程。选择性水解的较适宜反应条件为:22.83g,m(2)∶m(IPA-750)=6∶1,pH7.0,于30℃反应5h,产物为N-苯乙酰-D-苯丙氨酸(4)和L-苯丙氨酸(3,收率63%,光学纯度99%)。4用6mol·L-1盐酸于120℃水解反应8h,经脱盐处理得5,收率67%,光学纯度91%。3在含醋酸酐的醋酸溶液中进行消旋化处理,得到100%消旋的1可继续进行下一轮酶法拆分。 相似文献
35.
Alessandra BassoLuigi De Martin Cynthia EbertLucia Gardossi Paolo LindaFabrizio Sibilla 《Tetrahedron letters》2003,44(31):5889-5891
A novel application of organically modified silicates for covalent immobilisation of penicillin G acylase is reported. The immobilisation is efficient and the enzymatic preparation shows high specific activity and thermal stability. The technique opens new perspectives for the preparation of innovative tailor-made supports matching specific requirements of enzymatic processes. 相似文献
36.
A procedure is described for the immobilization of benzylpenicillin acylase from Escherichia coli within uniformly spherical, porous polyacrylamide gel beads. Aqueous solutions of the enzyme and sodium alginate and of acrylamide monomer, N,N'-methylene-bis-acrylamide, N,N,N,N'-tetramethylethylenediamine (TEMED) and sodium alginate are cooled separately, mixed, and dropped immediately into ice-cold, buffered calcium formate solution, pH 8.5, to give calcium alginate-coated beads. The beads are left for 30-60 min in the cold calcium formate solution for polyacrylamide gel formation. The beads are then treated with a solution of glutaraldehyde and the calcium alginate subsequently leached out with a solution of potassium phosphate. Modification of the native enzyme with glutaraldehyde results in a slight enhancement in the rate of hydrolysis of benzylpenicillin at pH 7.8 and 0.05M substrate concentration. The enzyme entrapped in porous polyacrylamide gel beads shows no measurable diffusional limitation in stirred reactors, catalyzing the hydrolysis of the substrate at a rate comparable to that of the glutaraldehyde-modified native enzyme. The immobilized enzyme preparation has been used in batch mode over 90 cycles without any apparent loss in hydrolytic activity. 相似文献
38.
Transfer of six thin-layer chromatography (TLC) Global Pharma Health Fund E.V. Minilab manual protocols for detecting fake drugs in pharmaceutical products to quantitative high-performance TLC (HPTLC)-densitometry methods was performed following a previously published model process. The developed and validated methods for tablets or capsules containing atenolol, chloramphenicol, furosemide, glibenclamide, penicillin V potassium, and praziquantel involved use of a limited list of inexpensive, relatively nontoxic, readily available solvents and other reagents; silica gel 60?F254 plates; automated bandwise sample and standard solution application; ascending mobile phase development of plates in a chamber; and automated slit scanning densitometry for detection, identification, and quantification. Validation data for methods developed in an early version of the transfer model process that did not include standard addition validation are reported for pharmaceutical products containing amitriptyline HCl, amodiaquine, diphenhydramine HCl, and mebendazole. 相似文献
39.
GonÇalves Luciana R. B. Fernandez-Lafuente Roberto Guisán Jose M. Giordano Raquel L. C. 《Applied biochemistry and biotechnology》2000,84(1-9):931-945
We presenta kinetic model for the synthesis of amoxicillin from p-hydroxyphenylglycine methyl ester and 6-aminopenicillanic acid, catalyzed by penicillin G acylase immobilized on agarose,
at 25°C. Michaelis-Menten kinetic parameters (with and without inhibition) were obtained from initial velocity data (pH 7.5
and 6.5). Amoxicillin synthesis reactions were used to validate the kinetic model after checking mass transport effects. A
reasonable representation of this system was achieved under some operational conditions, but the model failed under others.
Nevertheless, it will be useful whenever a simplified model is required, e.g., in model-based control algorithms for the enzymatic
reactor. 相似文献
40.