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201.
Sari MM 《Applied biochemistry and biotechnology》2011,163(8):1020-1037
Cupric ion-chelated poly(hydroxyethyl methacrylate-n-vinyl imidazole) (poly(HEMA-VIM)) microspheres prepared by suspension polymerization were investigated as a specific adsorbent
for immobilization of yeast invertase in a batch system. They were characterized by scanning electron microscopy, surface
area, and pore size measurements. They have spherical shape and porous structure. The specific surface area of the p(HEMA-VIM)
spheres was found to be 81.2 m2/g with a size range of 70–120 μm in diameter, and the swelling ratio was 86.9%. Then, Cu(II) ion chelated on the microspheres
(546 μmol Cu(II)/g), and they were used in the invertase adsorption. Maximum invertase adsorption was 51.2 mg/g at pH 4.5.
Cu(II) chelation increases the tendency from Freundlich-type to Langmuir-type adsorption model. The optimum activity for both
free and adsorbed invertase was observed at pH 4.5. The optimum temperature for the poly(HEMA-VIM)/Cu(II)-invertase system
was found to be at 55 °C, 10 °C higher than that of the free enzyme at 45 °C. V
max values were determined as 342 and 304 U/mg enzyme, for free and adsorbed invertase, respectively. K
m values were found to be same for free and adsorbed invertase (20 mM). Thermal and pH stability and reusability of invertase
increased with immobilization. 相似文献
202.
Anak Agung Istri Ratnadewi Muchzainal Fanani Sari Dewi Kurniasih Makiko Sakka Eddy Bagus Wasito Kazuo Sakka Zeily Nurachman Ni Nyoman Tri Puspaningsih 《Applied biochemistry and biotechnology》2013,170(8):1950-1964
The gene encoding a thermostable β-d-xylosidase (GbtXyl43B) from Geobacillus thermoleovorans IT-08 was cloned in pET30a and expressed in Escherichia coli; additionally, characterization and kinetic analysis of GbtXyl43B were carried out. The gene product was purified to apparent homogeneity showing M r of 72 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme exhibited an optimum temperature and pH of 60 °C and 6.0, respectively. In terms of stability, GbtXyl43B was stable at 60 °C at pH 6.0 for 1 h as well as at pH 6–8 at 4 °C for 24 h. The enzyme had a catalytic efficiency (k cat/K M) of 0.0048?±?0.0010 s?1 mM?1 on p-nitrophenyl-β-d-xylopyranoside substrate. Thin layer chromatography product analysis indicated that GbtXyl43B was exoglycosidase cleaving single xylose units from the nonreducing end of xylan. The activity of GbtXyl43B on insoluble xylan was eightfold higher than on soluble xylan. Bioinformatics analysis showed that GbtXyl43B belonging to glycoside hydrolase family 43 contained carbohydrate-binding module (CBM; residues 15 to 149 forming eight antiparallel β-strands) and catalytic module (residues 157 to 604 forming five-bladed β-propeller fold with predicted catalytic residues to be Asp287 and Glu476). CBM of GbtXyl43B dominated by the Phe residues which grip the carbohydrate is proposed as a novel CBM36 subfamily. 相似文献
203.
Stable neutral double hydrophilic block copolymer capillary coating for capillary electrophoretic separations
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Katriina Lipponen Sari Tähkä Mauri Kostiainen Marja‐Liisa Riekkola 《Electrophoresis》2014,35(8):1106-1113
Quaternized diblock copolymer, poly(N‐methyl‐2‐vinylpyridinium iodide‐block‐ethylene oxide), was successfully used as a neutral, dynamic coating to suppress the electroosmotic flow. The block copolymer consisted of two polymers that were linked covalently together. The cationic block (poly(N‐methyl‐2‐vinylpyridinium iodide)) was bound efficiently to the negatively charged capillary wall via electrostatic interactions, and the hydrophilic block (ethylene oxide) stabilized the system and created a neutral capillary surface with ultralow electroosmotic flow (+2.0 ± 4.5 × 10?10 m2/Vs). The main advantages of the coating were simple and fast preparation, easy regeneration and automation, and stable electroosmotic flow. To emphasize the potential of this type of coating its stability was measured at a wide pH range demonstrating a high stability in the pH range of 4.0–10.5 and lifetime up to 8 days. The successful studies carried out with beta‐blockers, basic proteins, and lipoproteins proved the suitability of the coating for the separation of different sized analytes. Furthermore, the neutral coating developed is useful in a wide range of protein analysis and biological interaction studies under physiological condition. 相似文献
204.
Faisal N. Al-Obaidi Hasan Atabey Mustafa Macit Hayati Sari 《Journal of solution chemistry》2014,43(5):989-999
The protonation equilibria of (2Z, 3Z)-2H-benzo[b][1,4]thiazine-2,3(4H)-dionedioxime (BTDH2) together with the equilibria of its bis- binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) were investigated potentiometrically. The investigation was carried out at 25 ± 0.1 °C, in aqueous solution, with a constant ionic strength of 0.100 mol·dm?3 NaCl. The protonation constants of the ligand together with the stability constants of a variety of complexes were determined potentiometrically in 10 % ethanol–water mixed solution using the SUPERQUAD computer program. Theoretical calculations were set up to assist in understanding the protonation sequence in the ligand molecule via the semi-empirical molecule orbital method of parameterized model number 3. Results are discussed in connection to the basicity of the donor atoms and structural arrangement of the ligand. Although BTDH2 has two dissociable protons, four protonation constants can be measured under the experimental conditions presented. These four protonation constants (as log10 βs) are 10.245, 19.397, 22.414 and 25.176. 相似文献
205.
Fatemeh Bootorabi Janne Jänis Jarkko Valjakka Sari Isoniemi Pirjo Vainiotalo Daniela Vullo Claudiu T Supuran Abdul Waheed William S Sly Onni Niemelä Seppo Parkkila 《BMC biochemistry》2008,9(1):1-8
Background
Bacillus thuringiensis Cry1Aa insecticidal protein is the most active known B. thuringiensis toxin against the forest insect pest Lymantria dispar (gypsy moth), unfortunately it is also highly toxic against the non-target insect Bombyx mori (silk worm).Results
Surface exposed hydrophobic residues over domains II and III were targeted for site-directed mutagenesis. Substitution of a phenylalanine residue (F328) by alanine reduced binding to the Bombyx mori cadherin by 23-fold, reduced biological activity against B. mori by 4-fold, while retaining activity against Lymantria dispar.Conclusion
The results identify a novel receptor-binding epitope and demonstrate that virtual elimination of binding to cadherin BR-175 does not completely remove toxicity in the case of B. mori. 相似文献206.
Ibrahim Narin Salih Sarioglan Beril Anilanmert Hayati Sari 《Journal of solution chemistry》2010,39(10):1582-1588
The pK
a constants and relative abundances of unionized and ionized forms of Montelukast sodium {the sodium salt of 2-[1-[[(1R)-1-[3-[2-(7-chloroquinolin-2-yl)ethenyl] phenyl]-3-[2-(2-hydroxypropan-2-yl)phenyl]propyl]sulfanylmethyl]cyclopropyl]acetic
acid} and Levodropropizine {(2S)-3-(4-phenylpiperazin-1-yl)propane-1,2-diol} were determined potentiometrically from measurements at various pHs. These determinations
were in order to relate their pK
a values with their bioavailability and to provide chemical data to be used in their analysis. 相似文献