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ABSTRACT: Emulsions composed of an ionic liquid (IL) 3-methyl-1-octylimidazolium hexafluorophosphate, water, and surfactant TX-100 (poly(ethylene glycol)-tert-octylphenyl) were studied by laser confocal scanning microscopy, stability determination and electrical conductivity. Multiple water-in-ionic liquid-in-water (W/IL/W) emulsions were formed around water volume fractions ~0.70. Further studies showed that the W/IL/W multiple emulsions were formed through an inversion between water-in-IL emulsion and IL-in-water emulsion.
Journal of Colloid and Interface Science 12/2011; 368(1):395-9. · 3.07 Impact Factor
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ABSTRACT: High-internal-ionic liquid-phase emulsions were formed for the first time. The novel emulsions are very stable and do not involve any volatile organic solvent. They have great potential of applications in different fields, such as material synthesis, extraction, encapsulation, and chemical reactions.
Chemical Communications 12/2011; 48(7):994-6. · 6.17 Impact Factor
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ABSTRACT: Tailor-made emulsion: A CO(2) -in-ionic-liquid microemulsion was produced for the first time. The CO(2) -swollen micelles are "tunable" because the micellar size can be easily adjusted by changing the pressure of CO(2) . The microemulsion has potential applications in materials synthesis, chemical reactions, and extraction.
Angewandte Chemie International Edition 09/2011; 50(42):9911-5. · 13.45 Impact Factor
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ABSTRACT: CO(2) can be used to separate surfactant and organic solvent completely in various surfactant/solvent solutions without contaminating the surfactants and solvents. We believe that the simple, efficient, and greener method has wide applications.
Chemical Communications 05/2011; 47(20):5816-8. · 6.17 Impact Factor
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ABSTRACT: The micellization of amphiphilic molecules is an interesting topic from both theoretical and practical points of view. Herein we have studied the effects of compressed CO(2) on the micellization of Pluronics in water by means of fluorescence, UV/Vis spectra, and small-angle X-ray scattering. It was found that CO(2) can induce the micellization of Pluronics in water, and the micelle can return to the initial state of molecular dispersion after depressurization. Therefore, the micellization of Pluronics in water can be switched through the easy control of pressure. Different from the common micelles with hydrophobic cores, interestingly, this CO(2)-induced micelle has an amphiphilic core, in which hydrophobic and hydrophilic domains coexist. On account of the ability to dissolve both polar and nonpolar components in the micellar core, the CO(2)-induced micelles can improve the reagent compatibilities frequently encountered in various applications. In an attempt to address this advantage, this micelle was utilized as template to the one-step synthesis of Au/silica core-shell composite nanoparticles. Furthermore, the underlying mechanism for the CO(2)-induced micellization of Pluronics in water was investigated by a series of experiments.
Chemistry 03/2011; 17(15):4266-72. · 5.93 Impact Factor
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ABSTRACT: Herein it was found that CO(2) could trigger an O/W to W/O emulsion inversion via a W/O/W nanoemulsion. In comparison with the conventionally used liquid or solid additives, the unusual advantage of this method is that the emulsion morphologies can be switched reversibly by the control of CO(2) pressure. Besides, CO(2) can be easily removed by depressurization and thus no extra separation process is needed, and CO(2) can be recycled. Furthermore, other lipophilic gases of ethylene, propylene and isobutane can also induce the O/W to W/O emulsion inversion. A possible mechanism for the gas-triggered emulsion inversion was proposed.
Physical Chemistry Chemical Physics 02/2011; 13(13):6065-70. · 3.57 Impact Factor
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Angewandte Chemie International Edition 01/2011; 50(3):636-9. · 13.45 Impact Factor
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Yueju Zhao,
Yunhua Zhang,
Yang Cao,
Jianxun Qi,
Liangwei Mao,
Yanfen Xue,
Feng Gao,
Hao Peng,
Xiaowei Wang,
George F Gao,
Yanhe Ma
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ABSTRACT: Significant progress has been made in isolating novel alkaline β-mannanases, however, there is a paucity of information concerning the structural basis for alkaline tolerance displayed by these β-mannanases. We report the catalytic domain structure of an industrially important β-mannanase from the alkaliphilic Bacillus sp. N16-5 (BSP165 MAN) at a resolution of 1.6 Å. This enzyme, classified into subfamily 8 in glycosyl hydrolase family 5 (GH5), has a pH optimum of enzymatic activity at pH 9.5 and folds into a classic (β/α)(8)-barrel. In order to gain insight into molecular features for alkaline adaptation, we compared BSP165 MAN with previously reported GH5 β-mannanases. It was revealed that BSP165 MAN and other subfamily 8 β-mannanases have significantly increased hydrophobic and Arg residues content and decreased polar residues, comparing to β-mannanases of subfamily 7 or 10 in GH5 which display optimum activities at lower pH. Further, extensive structural comparisons show alkaline β-mannanases possess a set of distinctive features. Position and length of some helices, strands and loops of the TIM barrel structures are changed, which contributes, to a certain degree, to the distinctly different shaped (β/α)(8)-barrels, thus affecting the catalytic environment of these enzymes. The number of negatively charged residues is increased on the molecular surface, and fewer polar residues are exposed to the solvent. Two amino acid substitutions in the vicinity of the acid/base catalyst were proposed to be possibly responsible for the variation in pH optimum of these homologous enzymes in subfamily 8 of GH5, identified by sequence homology analysis and pK(a) calculations of the active site residues. Mutational analysis has proved that Gln91 and Glu226 are important for BSP165 MAN to function at high pH. These findings are proposed to be possible factors implicated in the alkaline adaptation of GH5 β-mannanases and will help to further understanding of alkaline adaptation mechanism.
PLoS ONE 01/2011; 6(1):e14608. · 4.09 Impact Factor
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ABSTRACT: A xylanase gene (xyn10) from alkaliphilic Bacillus sp. N16-5 was cloned and expressed in Pichia pastoris. The deduced amino acid sequence has 85% identity with xylanase xyn10A from B. halodurans and contains two potential N-glycosylation sites. The glycosylated Xyn10 with MW 48 kDa can hydrolyze birchwood and oatspelt xylan. The enzyme had optimum activity at pH 7 and 70°C, with the specific activity of 92.5U/mg. The Xyn10 retained over 90% residual activity at 60°C for 30 min but lost all activity at 80°C over 15 min. Most tested ions showed no or slight inhibition effects on enzyme activity.
Biotechnology Letters 12/2010; 32(12):1915-20. · 1.68 Impact Factor
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Chemical Communications 11/2010; 47(3):1033-5. · 6.17 Impact Factor
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ABSTRACT: The cetyltrimethylammonium bromide (CTAB)/water/heptane emulsion system with different CO(2) pressure has been studied. The phase behavior investigation shows the nanoemulsion can be formed at suitable pressure range. The generalized indirect Fourier transformation (GIFT) analysis of the small-angle X-ray scattering (SAXS) data has drawn a clear picture of the structural information of the nanoemulsion, which reveals that the droplet of emulsion has a double structure with both the outer and inner droplet size in nanometre range. Furthermore, the investigation of the heptane/CTAB/water/CO(2) emulsion system by using electrical conductivity confirms the emulsion type transforms from O/W to W/O/W. In addition, the effect of different CTAB concentration on the nanoemulsion formation has been studied. It is found that enough CTAB concentration is necessary for the inclusion of continuous water into oil droplets. We also explored the application of the W/O/W double nanoemulsion in material synthesis. Interestingly, the hollow silica spheres with double shells were obtained in this CO(2)-induced double nanoemulsion.
Physical Chemistry Chemical Physics 10/2010; 13(2):684-9. · 3.57 Impact Factor
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ABSTRACT: The effect of CO(2) on the microstructure of L-alpha-phosphatidylcholine (lecithin) reverse micelles was studied. The small-angle X-ray scattering (SAXS) results show that CO(2) could induce a cylindrical-to-spherical micellar shape transformation. Fourier transform infrared (FT-IR) and UV-vis techniques were also utilized to investigate intermolecular interactions and micropolarity in the reverse micelles at different CO(2) pressures. The reduction of the degree of hydrogen bonding between surfactant headgroups and water with added CO(2) was found to be the main reason for the micellar shape transformation. In the absence of CO(2), the hydrogen bonding between water and P=O of lecithin forms a linking bridge in the interfacial layer. Therefore, the free movement of the polar head of lecithin is limited and the cylindrical reverse micelles are formed. Upon adding CO(2) to the reverse micelles, the hydrogen bonds between lecithin and water in reverse micelles are destroyed, which is favorable to forming spherical micelles. Moreover, the CO(2)-combined reverse micelles were utilized in the synthesis of silica particles. Rodlike silica nanoparticles were obtained in the absence of CO(2), and ellipsoidal and spherical mesoporous silica particles were formed in the presence of CO(2). This method of tuning micellar shape has many advantages compared to traditional methods.
Langmuir 03/2010; 26(7):4581-5. · 4.19 Impact Factor
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ABSTRACT: The study of the micelle-to-vesicle transition (MVT) is of great importance from both theoretical and practical points of view. Herein, we studied the effect of compressed CO(2) on the aggregation behavior of dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactants in aqueous solution by means of direct observation, turbidity and conductivity measurements, steady-state fluorescence, time-resolved fluorescence quenching (TRFQ), fluorescence quantum yield, and template methods. Interestingly, all these approaches showed that compressed CO(2) could induce the MVT in the surfactant system, and the vesicles returned to the micelles simply by depressurization; that is, CO(2) can be used to switch the MVT reversibly by controlling pressure. Some other gases, such as methane, ethylene, and ethane, could also induce the MVT of the surfactant solution. A possible mechanism is proposed on the basis of the packing-parameter theory and thermodynamic principles. It is shown that the mechanism of the MVT induced by a nonpolar gas is different from the MVT induced by polar and electrolyte additives.
Chemistry 12/2009; 16(4):1296-305. · 5.93 Impact Factor
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ABSTRACT: Beta-mannanases (beta-1,4-D-mannanase, EC 3.2.1.78), as a hemicellulose hydrolase, are widely distributed in bacteria, fungi, plants and even animals. They can randomly hydrolyze the beta-1,4-mannosidic linkages in mannan and heteromannan and have great potential in the food/feed, pulp/paper, medicine, oil exploitation and detergent industries. Most beta-mannanases often display a modular organization and usually contain structurally discrete catalytic and non-catalytic modules. Catalytic domains of these enzymes share a (beta/alpha)8-barrel fold, which play important roles in substrate binding and catalysis. Carbohydrate binding modules, as the most common non-catalytic modules, fold as beta-sandwich and facilitate the targeting of these enzymes to polysaccharide. In this review, a brief introduction is given concerning structural characteristics and function of these beta-mannanase modules.
ACTA MICROBIOLOGICA SINICA 09/2009; 49(9):1131-7.
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ABSTRACT: Monodisperse hollow silica spheres of uniform size and ordered mesoporous shells have been successfully fabricated in water/heptane/CTAB nanoemulsions induced by compressed CO(2).
Chemical Communications 06/2009; · 6.17 Impact Factor
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ABSTRACT: In this work, we studied the effect of compressed CO2 on the stability of vesicles formed in a dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactant system by combination of phase behavior and turbidity study, and UV-vis and fluorescence techniques. It was discovered that compressed CO2 could enhance the stability of vesicles significantly. This new and effective method to stabilize vesicles has some unique advantages over conventional methods. For example, the size and stability of the vesicles can be easily controlled by CO2 pressure; the method is greener because CO2 is a green reagent and it can be released completely after depressurization, which simplifies postseparation processes in applications. The main reason for CO2 to stabilize the vesicles is that CO2 molecules can insert into the hydrophobic bilayer region to enhance the rigidity of the vesicle film and reduce the size of the vesicles, which is different from that of conventional cosolvents (e.g., alcohols) used to stabilize vesicles. On the basis of this discovery, we developed a method to prepare hollow silica spheres using tetraethoxysilane as the precursor and CO2-stabilized vesicles as the template, in which CO2 acts as both the stabilizer of the vesicular template and the catalyst for the hydrolysis reaction of the precursor, and other cosolvents and catalysts are not required. Besides, the size of the silica hollow spheres prepared can be controlled by the pressure of CO2.
Langmuir 01/2009; 25(1):196-202. · 4.19 Impact Factor
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Angewandte Chemie International Edition 12/2008; 47(52):10119-23. · 13.45 Impact Factor
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ABSTRACT: The catalytic domain of an alkaline beta-mannanase from the alkaliphilic Bacillus sp. N16-5 has been expressed and purified. The recombinant enzyme was crystallized using the hanging-drop vapour-diffusion method at 298 K. X-ray diffraction data were collected to 1.6 A resolution. The crystal belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 59.03, b = 63.31, c = 83.34 A. Initial phasing was carried out by molecular replacement using the three-dimensional structure of a mannanase from the alkaliphilic Bacillus sp. JAMB602 as a search model.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 11/2008; 64(Pt 10):957-9. · 0.51 Impact Factor
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ABSTRACT: Lecithin is a very useful biosurfactant. In this work, the effects of compressed CO 2 on the critical micelle concentration (cmc) of lecithin in cyclohexane and solubilization of water, lysozyme, and PdCl 2 in the lecithin reverse micelles were studied. The micropolarity and pH value of the polar cores of the reverse micelles with and without CO 2 were also investigated. It was found that CO 2 could reduce the cmc of the micellar solution and enhance the capacity of the reverse micelles to solubilize water, the biomolecule, and the inorganic salt significantly. Moreover, the water pools could not be formed in the reverse micelles in the absence of CO 2 because of the limited amount of water solubilized. However, the water pools could be formed in the presence of CO 2 because large amounts of water could be solubilized. All of these provide more opportunity for effective utilization of this green surfactant. The possible mechanism for tuning the properties of the reverse micelles by CO 2 is discussed.
Langmuir 09/2008; 24(17):9328-33. · 4.19 Impact Factor
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ABSTRACT: A thermophilic, alkaliphilic and catalase-positive bacterium, designated strain HA6(T), was isolated from a hot spring in China. The strain was aerobic and chemo-organotrophic and grew optimally at 60 degrees C, pH 8.5 and 1.5 % (w/v) NaCl. The cells were Gram-positive rods, forming single terminal endospores. The predominant cellular fatty acids were iso-C(15 : 0) and iso-C(17 : 0). The cell-wall peptidoglycan contained meso-diaminopimelic acid. The genomic DNA G+C content was 45.2 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain HA6(T) formed a distinct lineage within the family Bacillaceae and was most closely related to Bacillus horti K13(T) and Bacillus smithii DSM 4216(T), with sequence similarities of 91.8 and 93.1 %, respectively. On the basis of its physiological and molecular properties, strain HA6(T) should be placed in a novel genus and species, for which the name Caldalkalibacillus thermarum gen. nov., sp. nov. is proposed. The type strain of Caldalkalibacillus thermarum is strain HA6(T) (=CGMCC 1.4242(T)=JCM 13486(T)).
International journal of systematic and evolutionary microbiology 07/2006; 56(Pt 6):1217-21. · 2.27 Impact Factor
