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11.
Alexander V. Vakurov Alexander K. Gladilin Johann Partridge Vadim V. Mozhaev Andrey V. Levashov Peter J. Halling 《Biotechnology Techniques》1996,10(8):621-624
Summary When free chymotrypsin is used to catalyse hydrolysis of N-acetyl tyrosine ethyl ester in 90% acetonitrile, the reaction rate soon falls because of the accumulation of the acidic product. If the enzyme is used in the form of a suspended complex with polyacrylic acid, the polyelectrolyte acts as an acid-base buffer to permit extended reaction. 相似文献
12.
Boris A. Dmitriev Andrey V. Nikolaev Alexander S. Shashkov Nikolay K. Kochetkov 《Carbohydrate research》1982,100(1):195-206
Successive condensation of derivatives of the trisaccharide, biological repeating-unit of the O-antigenic polysaccharide of Salmonella newington, followed by removal of protecting groups, has given the hexa- and nona-saccharides. The structures of these oligosaccharides were confirmed chemically and by 13C-n.m.r. spectroscopy. 相似文献
13.
Andrey A. Rosenkranz Sergey V. Yachmenev David A. Jans Natalya V. Serebryakova Vitaly I. Murav''ev Reiner Peters Alexander S. Sobolev 《Experimental cell research》1992,199(2):323-329
A soluble construct consisting of a plasmid carrying the gene of the SV40 large T-antigen and an insulin-poly-L-lysine conjugate is able to selectively transfect PLC/PRF/5 human hepatoma cells which possess insulin receptors. Transfection can be efficiently competed by excess free insulin. To examine intracellular transport of the construct, it was fluorescently labeled and its accumulation on and in cells visualized by video-enhanced microscopy and quantitative confocal laser scanning microscopy. After 2 h at 37 degrees C, the labeled construct was found predominantly in intracellular acidic compartments, with a substantial portion of fluorescence localized both near and in the cell nucleus. Binding, endocytosis, and nuclear localization of the labeled conjugate could all be competed by excess free insulin, thus indicating that entry of the conjugate into cells was specifically mediated by the insulin receptor. 相似文献
14.
Broad host range vectors derived from an RSF1010::Tn1 plasmid 总被引:2,自引:0,他引:2
15.
Formation of noncovalent complexes between tyrosinase from mushrooms and a cationic polyelectrolyte, polybrene (PB, poly (1,5-dimethyl-1,5-diazaundecamethyelene) bromide), was shown to activate and stabilize tyrosinase in water-ethanol mixtures. In the reaction of catechol oxidation in aqueous solutions, catalytic activity (k(cat)) of tyrosinase-PB complex ([PB]/[tyrosinase] molar ratio 100:1, per mole of polymer) in a wide range of pH was higher than that of free tyrosinase. In aqueous solutions and in water-ethanol mixtures at moderate concentrations of ethanol (10-40% v/v), the value of k(cat) of tyrosinase-PB complex exceeded the activity of free enzyme, from 1.2-2-fold, accompanied by the essential (up to 10-fold) increase in the value of the specificity constant (k(cat)/K(m)). The results are of practical importance for the construction of biocatalysts working successfully in polar organic media. 相似文献
16.
17.
Oligonucleotides composed of 2′-O-methyl and locked nucleic acid residues complementary to HIV-1 trans-activation responsive element TAR block Tat-dependent trans-activation in a HeLa cell assay when delivered by cationic lipids. We describe an improved procedure for synthesis and purification under highly denaturing conditions of 5′-disulphide-linked conjugates of 3′-fluorescein labelled oligonucleotides with a range of cell-penetrating peptides and investigate their abilities to enter HeLa cells and block trans-activation. Free uptake of 12mer OMe/LNA oligonucleotide conjugates to Tat (48–58), Penetratin and R9F2 was observed in cytosolic compartments of HeLa cells. Uptake of the Tat conjugate was enhanced by N-terminal addition of four Lys or Arg residues or a second Tat peptide. None of the conjugates entered the nucleus or inhibited trans-activation when freely delivered, but inhibition was obtained in the presence of cationic lipids. Nuclear exclusion was seen for free delivery of Tat (48–58), Penetratin and R9 conjugates of 16mer phosphorothioate OMe oligonucleotide. Uptake into human fibroblast cytosolic compartments was seen for Tat, Penetratin, R9F2 and Transportan conjugates. Large enhancements of HeLa cell uptake into cytosolic compartments were seen when free Tat peptide was added to Tat conjugate of 12mer OMe/LNA oligonucleotide or Penetratin peptide to Penetratin conjugate of the same oligonucleotide. 相似文献
18.
19.
Luiz Henrique Soares de Andrade Wilson Max Almeida Monteiro de Moraes Eduardo Hiroshi Matsuo Junior Elizabeth de Orleans Carvalho de Moura Hanna Karen Moreira Antunes Jairo Montemor Ednei Luiz Antonio Danilo Sales Bocalini Andrey Jorge Serra Paulo José Ferreira Tucci Patricia Chakur Brum Alessandra Medeiros 《Molecular and cellular biochemistry》2015,402(1-2):193-202
20.
Andrey M. Grishin Eunice Ajamian Linhua Zhang Isabelle Rouiller Mihnea Bostina Miroslaw Cygler 《The Journal of biological chemistry》2012,287(45):37986-37996
Microbial anaerobic and so-called hybrid pathways for degradation of aromatic compounds contain β-oxidation-like steps. These reactions convert the product of the opening of the aromatic ring to common metabolites. The hybrid phenylacetate degradation pathway is encoded in Escherichia coli by the paa operon containing genes for 10 enzymes. Previously, we have analyzed protein-protein interactions among the enzymes catalyzing the initial oxidation steps in the paa pathway (Grishin, A. M., Ajamian, E., Tao, L., Zhang, L., Menard, R., and Cygler, M. (2011) J. Biol. Chem. 286, 10735–10743). Here we report characterization of interactions between the remaining enzymes of this pathway and show another stable complex, PaaFG, an enoyl-CoA hydratase and enoyl-Coa isomerase, both belonging to the crotonase superfamily. These steps are biochemically similar to the well studied fatty acid β-oxidation, which can be catalyzed by individual monofunctional enzymes, multifunctional enzymes comprising several domains, or enzymatic complexes such as the bacterial fatty acid β-oxidation complex. We have determined the structure of the PaaFG complex and determined that although individually PaaF and PaaG are similar to enzymes from the fatty acid β-oxidation pathway, the structure of the complex is dissimilar from bacterial fatty acid β-oxidation complexes. The PaaFG complex has a four-layered structure composed of homotrimeric discs of PaaF and PaaG. The active sites of PaaF and PaaG are adapted to accept the intermediary components of the Paa pathway, different from those of the fatty acid β-oxidation. The association of PaaF and PaaG into a stable complex might serve to speed up the steps of the pathway following the conversion of phenylacetyl-CoA to a toxic and unstable epoxide-CoA by PaaABCE monooxygenase. 相似文献