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Bhiri F Chaabouni SE Limam F Ghrir R Marzouki N 《Applied biochemistry and biotechnology》2008,149(2):169-182
The Pol6 mutant of Penicillium occitanis fungus is of great biotechnological interest since it possesses a high capacity of cellulases and β-glucosidase production
with high cellulose degradation efficiency (Jain et al., Enzyme Microb Technol, 12:691–696, 1990; Hadj-Taieb et al., Appl Microbiol Biotechnol, 37:197–201, 1992; Ellouz Chaabouni et al., Enzyme Microb Technol, 16:538–542, 1994; Ellouz Chaabouni et al., Appl Microbiol Biotechnol, 43:267–269, 1995). In this work, two forms of β-glucosidase (β-glu 1 and β-glu 2) were purified from the culture supernatant
of the Pol6 strain by gel filtration, ion exchange chromatography, and preparative anionic native electrophoresis. These enzymes
were eluted as two distinct species from the diethylamino ethanol Sepharose CL6B and anionic native electrophoresis. However,
both behaved identically on sodium dodecyl sulfate polyacrylamide gel electrophoresis (MW, 98 kDa), shared the same amino
acid composition, carbohydrate content (8%), and kinetic properties. Moreover, they strongly cross-reacted immunologically.
They were active on cellobiose and pNPG with Km values of 1.43 and 0.37 mM, respectively. β-glu 1 and β-glu 2 were competitively inhibited by 1 mM of glucose and 0.03 mM
of δ-gluconolactone. They were also significantly inhibited by Hg2+ and Cu2 at 2 mM. The addition of purified enzymes to the poor β-glucosidase crude extract of Trichoderma reesei increased its hydrolytic efficiency on H3P04 swollen cellulose but had no effect with P. occitanis crude extract. Besides their hydrolytic activities, β-glu 1 and β-glu 2 were endowed with trans-glycosidase activity at high
concentration of glucose. 相似文献
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Synthesis, crystal structure, and dielectric properties of [C6H4(NH3)2]2ClBiCl6.H2O are reported. The compound crystallizes in the monoclinic system with space group P21/n. The unit cell dimensions are a = 9.836(5), b = 19.582(5), c = 13.082(5) ?, β = 104.731(5)° with Z = 4. The atomic arrangement can be described by an alternation of organic and inorganic layers. The anionic layer is built
up of octahedral of [BiCl6]3- arranged in sandwich between the organic layers. The crystal packing is governed by means of the ionic N–H···Cl hydrogen
bonds, forming a three-dimensional network. The dielectric properties have been investigated at temperature range from 297
to 410 K at various frequencies (10 Hz–100 kHz). Dielectric studies were performed to confirm results obtained with thermal
analysis. The evolution of dielectric constant as a function of temperature and frequency of single crystal has been investigated
in order to determine some related parameters. 相似文献
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Houcine ZoghlamiMoufida Romdhani-Younes Mohamed Moncef Chaabouni Ahmed Baklouti 《Tetrahedron letters》2011,52(8):881-883
The solvent-free reaction of oligoethylene glycol diglycidyl ethers with dimercaptoethane in the presence of benzyltrimethylammonium hydroxide (Triton B) gave, via regiospecific epoxide opening reactions, dihydroxy dithiacrown ethers in excellent yields and in short reaction times. 相似文献
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Chehrouri M Fillion JH Chaabouni H Mokrane H Congiu E Dulieu F Matar E Michaut X Lemaire JL 《Physical chemistry chemical physics : PCCP》2011,13(6):2172-2178
Nuclear spin conversion (NSC) of ortho- to para-H(2) and para- to ortho-D(2) has been investigated on an amorphous solid water (ASW) surface at 10 K, in the presence of co-adsorbed O(2). The dynamics of the nuclear spin conversion could be revealed by combination of resonance enhanced multiphoton ionization spectroscopy (REMPI) with temperature programmed desorption (TPD) experiments. The conversion rates are consistent with a diffusion of molecular hydrogen inducing a nuclear spin conversion enhanced in the vicinity of molecular oxygen. The conversion times were found to increase with decreasing O(2) and H(2) coverage. Finally, on oxygen free ASW surface, the extremely long conversion characteristic times measured showed that such surface is not an efficient catalyst for NSC, in contradiction with hypothesis commonly made for interstellar medium. 相似文献
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Penthylene diammonium pentachlorothallate(III) exhibits a phase transition at 316 K <artwork name="GPHT21157eu1"> This transition has been characterized by optical birefringence, dielectric measurements differential scanning calorimetry and spectroscopic measurements on polycrystalline samples. The space group and the cell parameters of phase I were determined by X-ray diffraction from single crystals. Phase I has space group P212121, with Z = 4, a = 7.696(3), b = 13.2890(17) and c = 13.503(18) Å. The transition is both displacive and order-disorder involving mainly conformational changes of the organic chain [NH3(CH2)5NH3]2+ coupled with distortion of the TlCl6 octahedra. This behaviour and the crystal dynamics will be discussed and compared with those found in the literature for homologous compounds. 相似文献
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Monofluorinated ethylenic compounds have been prepared by action of potassium tertiobutylate either on2-fluorotosylates or 2-fluorochlorides. In the case of 2-fluorochlorides the action, at higher temperature, of basic salt such as KF in ethylene glycol, may be used to prepare monofluorinated ethylenics compounds. 相似文献
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A convenient method for the one-pot conversion of olefins into the corresponding enol thioethers is reported. The products were obtained via the N-bromosuccinimide cobromination reaction of olefins with thiols in basic medium. Steric hindrance present in the product alkenes may explain the stereochemistry observed. 相似文献