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排序方式: 共有214条查询结果,搜索用时 15 毫秒
31.
Kulthida Kaewprapan Patoomratana Tuchinda Emmanuelle Marie Alain Durand Pranee Inprakhon 《Journal of Molecular Catalysis .B, Enzymatic》2007,47(3-4):135-142
The application of enzymatic catalysis for the synthesis of polysaccharide-based surfactants was investigated. The polysaccharide dextran, a neutral bacterial polysaccharide consisting of -1,6 linked glucose units, was chemically modified by the attachment of hydrophobic groups through a transesterification reaction with a vinyl decanoate. A screening of commercially available lipases and protease for the synthesis of amphiphilic polysaccharides in DMSO suggested that lipase AY from Candida rugosa modified dextran T-40 with vinyl decanoate at the highest conversion. A pH-adjustment in a phosphate buffer at pH 7.5 prior to use is crucial to make this enzyme active in DMSO. The effect of enzyme concentration and mole ratio of fatty ester to dextran T-40 on the conversion and the rate of reaction were studied. Finally, investigation of the kinetics and regioselectivity of lipase AY-catalyzed modification offer a possibility to regulate the position and the extent of hydrophobic group attached to dextran. These two properties are fundamental for controlling the physico-chemical properties of the final polymeric surfactants. 相似文献
32.
Kohji Ishihara Nobuyoshi Nakajima Toshiyuki Itoh Hitomi Yamaguchi Kaoru Nakamura Tsutomu Furuya Hiroki Hamada 《Journal of Molecular Catalysis .B, Enzymatic》1999,7(5-6):307-310
The practical synthesis of vinyl p-coumarate (vinyl 4-hydroxycinnamate) and vinyl ferulate (vinyl 4-hydroxy-3-methoxycinnamate) was accomplished via a transesterification to the corresponding aromatic acid using vinyl acetate and a catalytic amount of PdCl2, followed by the lipase-catalyzed regioselective alcoholysis in EtOH. 相似文献
33.
Nuclear lipid mediators: Role of nuclear sphingolipids and sphingosine‐1‐phosphate signaling in epigenetic regulation of inflammation and gene expression 下载免费PDF全文
34.
Paczkowski C Musial A Wlodkowski L Kalinowska M Wojciechowski ZA 《Biotechnology letters》2007,29(9):1403-1408
The regioselective acylation of cholesteryl β-d-glucoside, at the C-6 of the glucose moiety, was achieved using microbial lipases in organic solvents. With palmitic acid
as an acyl donor 81 or 63% conversions of cholesteryl glucoside to its 6′-O-palmitoyl derivative were obtained using Candida antarctica or Rhizomucor miehei enzymes, respectively. High yields (64–92%) were also obtained with fatty acids 6:0–22:0 and 16:1 (n-7). The synthesis of
cholesteryl (6′-O-palmitoyl)glucoside was also achieved via transesterification, using mono-, di- and tri-palmitoylglycerols or methyl and ethyl palmitate as acyl sources. With R. miehei lipase transesterification between methyl palmitate (80 mM) and cholesteryl glucoside (1 mM) proceeded after 24 h with a
nearly quantitative yield (97%). 相似文献
35.
《Bioorganic & medicinal chemistry》2016,24(21):5115-5126
Arylated coumarins were prepared by site-selective Suzuki–Miyaura cross-coupling reaction of the bis(triflate) of 4-methyl-6,7-dihydroxycoumarin. Triarylated coumarins were prepared by Suzuki–Miyaura cross-coupling reactions of 3-bromo-4-methyl-2-oxo-2H-chromene-6,7-diylbis(trifluoromethanesulfonate). The in vitro anti-HIV activity of the products was investigated. Two lead structures with considerable activities were identified. 相似文献
36.
《Bioscience, biotechnology, and biochemistry》2013,77(5):960-965
Chitin deacetylase (CDA), the enzyme that catalyzes the hydrolysis of acetamido groups of GlcNAc in chitin, was purified from culture filtrate of the fungus Mortierella sp. DY-52 and characterized. The extracellular enzyme is likely to be a highly N-glycosylated protein with a pI of 4.2–4.8. Its apparent molecular weight was determined to be about 52 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS–PAGE) and 67 kDa by size-exclusion chromatography. The enzyme had an optimum pH of 6.0 and an optimum temperature of 60 °C. Enzyme activity was slightly inhibited by 1–10 mM Co2+ and strongly inhibited by 10 mM Cu2+. It required at least two GlcNAc residues for catalysis. When (GlcNAc)6 was used as substrate, K m and V max were determined to be 1.1 mM and 54.6 μmol min?1 respectively. 相似文献
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39.
Nucleolar dominance and silencing of transcription 总被引:1,自引:0,他引:1
Pikaard CS 《Trends in plant science》1999,4(12):478-483
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