Various azo compounds(Modified dyes)have been synthesised by chemical modification of areca nut extract(epicate-chin),a plant-based Polyphenolic compound to get semi-synthetic dyes.Three different primary amines namel...Various azo compounds(Modified dyes)have been synthesised by chemical modification of areca nut extract(epicate-chin),a plant-based Polyphenolic compound to get semi-synthetic dyes.Three different primary amines namely p-nitro aniline,p-anisidine and aniline,were diazotized to form their corresponding diazonium salts which were further coupled with an areca nut extract.Preliminary characterization of the areca nut extract and the resultant azo compounds(Modified dyes)was carried out in terms of melting point,solubility tests,thin layer chromatography,UV-Visible and FTIR spectroscopy.These modified dyes were further applied on polyester and nylon fabrics and%dye exhaustion was evaluated.Dyed fabrics were further tested for their fastness properties such as wash fastness,rubbing fastness,light fastness and sublimation fastness.The results of the fastness tests indicate that,all the three modified dyes have good dyeability for polyester and nylon fabrics.The dyed fabrics were also tested for ultraviolet protection factor which showed very good ultraviolet protection.展开更多
Cellulose nanocrystals(CNCs) have been widely applied in biomaterials and show great biocompatibility and mechanical strength. In this review, the chemical reactions applied in CNC surface modification and their appli...Cellulose nanocrystals(CNCs) have been widely applied in biomaterials and show great biocompatibility and mechanical strength. In this review, the chemical reactions applied in CNC surface modification and their application in CNC based biomaterials are introduced. Furthermore, the conjugation of different functional molecules and nanostructures to the surface of CNCs are discussed, with focus on the binding modes, reaction conditions, and reaction mechanisms. With this introduction, we hope to provide a clear view of the strategies for surface modification of CNCs and their application in biomaterials, thus providing an overall picture of promising CNC-based biomaterials and their production.展开更多
Layered double hydroxides are one class or kind of 2 D layered materials that are considered promising for use in the supercapacitor.Although there have been many studies on the structure,composition,properties,and el...Layered double hydroxides are one class or kind of 2 D layered materials that are considered promising for use in the supercapacitor.Although there have been many studies on the structure,composition,properties,and electrode fabrication of layered double hydroxides,none summarize the effects of various modification methods on the structure and performance of layered double hydroxides in the supercapacitor.In a bid to fill this gap,in this review,we summarize the progress of modification methods such as exfoliation,intercalation,vacancy,doping,phase transformation,and composition regulation of layered double hydroxides in the field of the supercapacitor and put forward some opinions regarding the progress of research on the methods used in modifying the layered double hydroxides.展开更多
Superhydrophobic aluminum surfaces have been prepared by means of electrodeposition of copper on aluminum surfaces, followed by electrochemical modification using stearic acid organic molecules. Scanning electron micr...Superhydrophobic aluminum surfaces have been prepared by means of electrodeposition of copper on aluminum surfaces, followed by electrochemical modification using stearic acid organic molecules. Scanning electron microscopy(SEM) images show that the electrodeposited copper films follow "island growth mode" in the form of microdots and their number densities increase with the rise of the negative deposition potentials. At an electrodeposition potential of-0.2 V the number density of the copper microdots are found to be 4.5×104cm^(-2)that are increased to 2.9×105cm^(-2)at a potential of-0.8 V. Systematically, the distances between the microdots are found to be reduced from 26.6 μm to 11.03 μm with the increase of negative electrochemical potential from-0.2 V to-0.8 V. X-ray diffraction(XRD) analyses have confirmed the formation of copper stearate on the stearic acid modified copper films. The roughness of the stearic acid modified electrodeposited copper films is found to increase with the increase in the density of the copper microdots. A critical copper deposition potential of-0.6 V in conjunction with the stearic acid modification provides a surface roughness of 6.2 μm with a water contact angle of 157?, resulting in superhydrophobic properties on the aluminum substrates.展开更多
In the phosphate buffer solution of pH＞7,the cysteine sensitized the electrochemiluminescence (ECL) of luminol.It could be modified on the surface of platinum electrode and furthermore adsorbing the luminol on its e...In the phosphate buffer solution of pH＞7,the cysteine sensitized the electrochemiluminescence (ECL) of luminol.It could be modified on the surface of platinum electrode and furthermore adsorbing the luminol on its exterior to construct an ECL sensor.The ECL intensity of this sensor was strong enough and very stable.There wasn't obvious decrease of ECL intensity for thirty times of using in 48 hours with the relative standard deviation (RSD) of 0.98%.It could be used to determine some quenching effective molecules such as superoxide dismutase (SOD) with negative response upon the concentration range from 4.8 IU/ml to 57.6 IU/ml.展开更多
In this paper, the content of water glass before and after adding modifying agent was measured by Trimethylsilyl-gas-chromatography. The experimental results showed that different modulus of water glass could generate...In this paper, the content of water glass before and after adding modifying agent was measured by Trimethylsilyl-gas-chromatography. The experimental results showed that different modulus of water glass could generate different content of mono-silicate acid and oligomeric silicate acid in water glass. After a period of storage, different modulus of water glass led to decrease of silicate content at different levels. Because higher content of Na<sub>2</sub>O in water glass tended to incur the alkaline polymerization, the occurrence of depolymerization of silicate species would lead to an increase of oligomeric silicate species, resulting in a drawback of silicate species content after a period of storage. And contrary to that, lower content of Na<sub>2</sub>O in water glass tended to incur the acidic polymerization. When the modifying agent was added to the newly made water glass, the amount of mono-silicate acid and oligomeric silicate acid also decreased. In modified water glass, the change of each silicate acid species was less than that in unmodified water glass. These results showed that the modifying agent retarded the aging of water glass. It had remarkable significance on the theory and practical application of water glass chemistry.展开更多
Acylation has been shown to be an effective toolfor improving surface functional properties of plant proteins.Soy bean protein has been extensively modified throughchemical and enzvmatic treatments.Their effectiveness...Acylation has been shown to be an effective toolfor improving surface functional properties of plant proteins.Soy bean protein has been extensively modified throughchemical and enzvmatic treatments.Their effectiveness lies intheir high nutritional value and low cost,which promotetheir use as ingredients for the formulation of food products.This paper reports a complete review of chemical modificationof various proteins from plant and animal sources,The nutri-tive and toxicological aspects through in vitro and in vivotests are also described.展开更多
A linear a-D-(13)-glucan, named PSG, was obtained from the spores of Ganoderma lucidum. The synthesis of positively and negatively charged polyelectrolytes from PSG was developed. Amine groups and carboxymethyl groups...A linear a-D-(13)-glucan, named PSG, was obtained from the spores of Ganoderma lucidum. The synthesis of positively and negatively charged polyelectrolytes from PSG was developed. Amine groups and carboxymethyl groups were introduced through nucleophilic substitution with 3-chloropropylamine or chloroacetic acid, respectively. Reaction conditions were varied to obtain insight into the influence of variables on the degree of substitution.展开更多
Scrap vulcanized rubber is amongst a bigger waste polymers. It does not decompose easily owing to its cross linked structure. Modification of scrap tires powder by the grafting with 2-acrylamido-2-methylpropanesulfoni...Scrap vulcanized rubber is amongst a bigger waste polymers. It does not decompose easily owing to its cross linked structure. Modification of scrap tires powder by the grafting with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is described. The grafting is achieved through free radical initiation. The effects of different amount of monomer and initiator were examined. Also the influence of reaction time and temperature were investigated. The grafted waste rubber was characterized by FT/IR, SEM and DSC measurements. The proposed mechanism of the grafting reaction is discussed. From DSC and SEM studies of WR-g-AMPS compared with PAMPS and WR, the results show that the particle size and crystallinity were enhanced for the grafted copolymers. The obtained modified scraped tires will used as an ion exchanger for the future applications.展开更多
Tryptophan(Trp) residues in a pullulanase were modified by N-bromosuccinimide(NBS). The results of the Spande method indicate that there are 18 Trp residues in the pullulanase and nine of them are located on the surfa...Tryptophan(Trp) residues in a pullulanase were modified by N-bromosuccinimide(NBS). The results of the Spande method indicate that there are 18 Trp residues in the pullulanase and nine of them are located on the surface of the enzyme. Three of these Trp residues are nonessential residues which show the fastest reaction rate according to the Zou′s plot. Two of the seven relative faster reacting residues are essential for the activity of the enzyme. The other eight are the slowest in the reaction rate or non-reactive residues for the reaction. The fluorescence and circular dichroism(CD) spectra of the pullulanase have been changed after the reaction with NBS. Potassium iodide(KI) and acrylamide also have remarkable influences on the fluorescence spectra of the pullulanase.展开更多
The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerizat...The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 °C for 30 min in 15 mL 1 % PVA/H2O. Then 4.34 moi/L VAc was added dropwise and the reaction was allowed to proce at 48 °C for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.展开更多
To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium c...To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium carbonate as raw material was proposed.The effect of modifier reaction percentage, reaction time, calcining temperature and modifier amount on particle size, density, suspensibility, and hardness of compound CeO2 powder was investigated.The phase evolutions of preparation process were characterized by XRD.SEM micrograph of the final product shows that compound CeO2 powders obtained are well-dispersed, spherically-shaped, uniformly-sized and submicron-sized particles.The method is readily available in raw material, low in cost, simple in process, and has great potential for industrialization.The compound CeO2 powders of different physical properties can be synthesized by controlling the above-mentioned influence factors in preparation process.展开更多
Silicene is a two-dimensional(2D) material, which is composed of a single layer of silicon atoms with sp2–sp3mixed hybridization. The sp2–sp3mixed hybridization renders silicene excellent reactive ability, facilitat...Silicene is a two-dimensional(2D) material, which is composed of a single layer of silicon atoms with sp2–sp3mixed hybridization. The sp2–sp3mixed hybridization renders silicene excellent reactive ability, facilitating the chemical modification of silicene. It has been demonstrated that chemical modification effectively enables the tuning of the properties of silicene. We now review all kinds of chemical modification methods for silicene, including hydrogenation, halogenation,organic surface modification, oxidation, doping and formation of 2D hybrids. The effects of these chemical modification methods on the geometrical, electronic, optical, and magnetic properties of silicene are discussed. The potential applications of chemically modified silicene in a variety of fields such as electronics, optoelectronics, and magnetoelectronics are introduced. We finally envision future work on the chemical modification of silicene for further advancing the development of silicene.展开更多
Silk fibers have been grafted with ethylene glycol dimethacrylate (EGDMA) and characteristics of the grafted silk fibers were analyzed in relation to the graft yield on the basis of the tensile properties, dyeing beha...Silk fibers have been grafted with ethylene glycol dimethacrylate (EGDMA) and characteristics of the grafted silk fibers were analyzed in relation to the graft yield on the basis of the tensile properties, dyeing behaviour, durability during laundering and solubility of the specimen in NaOH solution. The amount of the acid dye absorbed by the fibers decreased with increasing graft yield, while the value of rating for washing fastness on silk fibers was almost unchanged by the graft treatment. The breaking loads of the fiber were almost unchanged whereas rigidity of the fibers increased after graft treatment. Graft treatment enhanced silk fiber durability during laundering and in NaOH solution.展开更多
Objective: To investigate the effects of acetylation and pregelatinization of cassava and sweet potato starches on the mechanical and release properties of directly compressed paracetamol tablet formulations in compar...Objective: To investigate the effects of acetylation and pregelatinization of cassava and sweet potato starches on the mechanical and release properties of directly compressed paracetamol tablet formulations in comparison with official corn starch.Methods: The native starches were modified by acetylation and pregelatinization. The tablets were assessed using friability(Fr), crushing strength(Cs), disintegration time(Dt) and dissolution parameters. Results: Starch acetylation produced paracetamol tablets that were stronger and had the best balance of mechanical and disintegration properties, while pregelatinization produced tablets that were more friable but had a better overall strength in relation to disintegration than formulations made from natural starches. Correlations mainly existed between Dt and the dissolution parameters t80, t2 and k1 in the formulations. Conclusions: Modification of the experimental starches improved the mechanical and release properties of directly compressed paracetamol tablet formulations. Thus, they can be developed for use as pharmaceutical excipients in specific formulations.展开更多
A new product PEGylated rhaFGF was obtained by site-directed chemical modification. When compared with unmodified rhaFGF, PEGylated rhaFGF showed comparable bioactivity and superior stability at 37°C in mouse ser...A new product PEGylated rhaFGF was obtained by site-directed chemical modification. When compared with unmodified rhaFGF, PEGylated rhaFGF showed comparable bioactivity and superior stability at 37°C in mouse serum and the stronger resistant potency to trypsin. This was accompanied by a substantial decreasing immunogenicity. Site-specific PEGylation of rhaFGF may increase its therapeutic potency in humans.展开更多
Tryptophan(Trp)residues in pullulanase have been chemically modified with N-bromo- ssuccinimide(NBS). The results of ultraviolet spectra indicated that there are 18 Trp residues in pullulanase and nine of them are loc...Tryptophan(Trp)residues in pullulanase have been chemically modified with N-bromo- ssuccinimide(NBS). The results of ultraviolet spectra indicated that there are 18 Trp residues in pullulanase and nine of them are located on the surface of the enzyme. Three of these Trp residues are none-essential residues which showed the fastest reaction speed by Zhou’s plot. Two of the seven relative faster reacting residues are essential for the activity of the enzyme. The other eight are none-reactive residues with lowest reaction speed.展开更多
Bio-based nanomaterial is more attractive, due to its abundance, eco-friendliness and sustainability, when compared to the non-renewable toxic petrochemicals used in the wood adhesive sector. Recent studies on the for...Bio-based nanomaterial is more attractive, due to its abundance, eco-friendliness and sustainability, when compared to the non-renewable toxic petrochemicals used in the wood adhesive sector. Recent studies on the formaldehyde emission by petrochemical binders in wood adhesives have attracted scientists for the research in biomaterial-based binders. In this aspect nanocellulose (NC) is one such material which has reinforcing ability and has natural binding properties. Conventional wood adhesive uses petrochemical-based binders and additives. Inclusion of nanocellulose in wood adhesive could drastically reduce the dependency on non-renewable petroleum sources. Even though wood adhesive uses NC for improving mechanical properties of the adhesive, usage is restricted because of its inability to enhance tackiness and adhesion compared with petrochemicals. Availability of free hydroxyl groups and feasibility for modification can be a potential way for functionalization of this nanomaterial. To improve adhesion properties and to make nanocellulose act as a functional filler, the crosslinking approach can be a possible solution. Enhancement of thermal properties with improved thermal degradation, water barrier properties of crosslinked films and enhanced mechanical properties especially in crosslinked poly (vinyl alcohol) (PVA) matrix, which is one of the binders for wood adhesive discussed in this review paper proves the potential applicability of crosslinked NC. Hence by inclusion of NC in wood adhesive and crosslinking with the binder, both mechanical and performance properties are expected to enhance which will create a new world and possibilities for the bio-based eco-friendly wood adhesives. In this review paper, we have reviewed the crosslinking of nanocellulose to enhance the performance of wood adhesives.展开更多
Acetylacetone was firstly introduced into the aqueous media with the presence of aluminum sec-butoxide and peptizator. It was confirmed that the UV (ultraviolet) absorption band of acetylacetone underwent 14 nm of red...Acetylacetone was firstly introduced into the aqueous media with the presence of aluminum sec-butoxide and peptizator. It was confirmed that the UV (ultraviolet) absorption band of acetylacetone underwent 14 nm of red-shift due to the formation of the six-membered ring of the complex between alumina and acetylacetone in the aqueous solution. It was also found that the chemical modification can be dissociated by the UV irradiation with a wavelength shorter than 286 nm as a result of the excitation of π-π* transition in the complex.展开更多
The amino acid composition of the superoxide dismutase(SOD) from camellia pollen was measured and the tryptophan(Trp) residues were modified by using N-bromosuccinimide(NBS). The results show that there are 21 Trp res...The amino acid composition of the superoxide dismutase(SOD) from camellia pollen was measured and the tryptophan(Trp) residues were modified by using N-bromosuccinimide(NBS). The results show that there are 21 Trp residues in an SOD molecule and seven of which are located on the surface of the enzyme. By researching the fluorescence spectra of the native SOD and the modified SOD, we have found that the emission wavelength of Trp is at 335 nm and the fluorescence intensity will decrease when the enzyme is modified. The results also show that potassium iodide(KI) can significantly quench the fluorescence of the native SOD, but it has a less pronounced effect on the modified enzyme. Glycerin as a surface activation reagent can stabilize the fluorescence of the modified enzyme.展开更多
基金We highly acknowledge the University Grants Commission-Special Assistance Programme(UGC-SAP)-BSR SECTION for fellowship.
文摘Various azo compounds(Modified dyes)have been synthesised by chemical modification of areca nut extract(epicate-chin),a plant-based Polyphenolic compound to get semi-synthetic dyes.Three different primary amines namely p-nitro aniline,p-anisidine and aniline,were diazotized to form their corresponding diazonium salts which were further coupled with an areca nut extract.Preliminary characterization of the areca nut extract and the resultant azo compounds(Modified dyes)was carried out in terms of melting point,solubility tests,thin layer chromatography,UV-Visible and FTIR spectroscopy.These modified dyes were further applied on polyester and nylon fabrics and%dye exhaustion was evaluated.Dyed fabrics were further tested for their fastness properties such as wash fastness,rubbing fastness,light fastness and sublimation fastness.The results of the fastness tests indicate that,all the three modified dyes have good dyeability for polyester and nylon fabrics.The dyed fabrics were also tested for ultraviolet protection factor which showed very good ultraviolet protection.
基金National Natural Science Foundation of China(51373131)Fundamental Research Funds for the Central Universities(XDJK2016A017,XDJK2016C033,and WUT-2014-II-009)+1 种基金Project of Basic Science and Advanced Technology Research,Chongqing Science and Technology Commission(cstc2016,jcyjA0796)the Talent Project of Southwest University(SWU115034)
文摘Cellulose nanocrystals(CNCs) have been widely applied in biomaterials and show great biocompatibility and mechanical strength. In this review, the chemical reactions applied in CNC surface modification and their application in CNC based biomaterials are introduced. Furthermore, the conjugation of different functional molecules and nanostructures to the surface of CNCs are discussed, with focus on the binding modes, reaction conditions, and reaction mechanisms. With this introduction, we hope to provide a clear view of the strategies for surface modification of CNCs and their application in biomaterials, thus providing an overall picture of promising CNC-based biomaterials and their production.
基金The authors gratefully acknowledge the financial support provided by the project of Technological Innovation and Application Development in Chongqing(cstc2019jscxmsxm0378)the National Natural Science Foundation of China(Grant No.21576034 and 51908092)+1 种基金the State Education Ministry and Fundamental Research Funds for the Central Universities(2019CDQYCL042,2019CDXYCL0031,106112017CDJXSYY0001,2018CDYJSY0055,106112017CDJQJ138802,106112017CDJSK04XK11,and 2018CDQYCL0027)the Joint Funds of the National Natural Science Foundation of China-Guangdong(Grant No.U1801254).
文摘Layered double hydroxides are one class or kind of 2 D layered materials that are considered promising for use in the supercapacitor.Although there have been many studies on the structure,composition,properties,and electrode fabrication of layered double hydroxides,none summarize the effects of various modification methods on the structure and performance of layered double hydroxides in the supercapacitor.In a bid to fill this gap,in this review,we summarize the progress of modification methods such as exfoliation,intercalation,vacancy,doping,phase transformation,and composition regulation of layered double hydroxides in the field of the supercapacitor and put forward some opinions regarding the progress of research on the methods used in modifying the layered double hydroxides.
基金the financial support provided by the Natural Sciences and Engineering Research Council of Canada(NSERC)
文摘Superhydrophobic aluminum surfaces have been prepared by means of electrodeposition of copper on aluminum surfaces, followed by electrochemical modification using stearic acid organic molecules. Scanning electron microscopy(SEM) images show that the electrodeposited copper films follow "island growth mode" in the form of microdots and their number densities increase with the rise of the negative deposition potentials. At an electrodeposition potential of-0.2 V the number density of the copper microdots are found to be 4.5×104cm^(-2)that are increased to 2.9×105cm^(-2)at a potential of-0.8 V. Systematically, the distances between the microdots are found to be reduced from 26.6 μm to 11.03 μm with the increase of negative electrochemical potential from-0.2 V to-0.8 V. X-ray diffraction(XRD) analyses have confirmed the formation of copper stearate on the stearic acid modified copper films. The roughness of the stearic acid modified electrodeposited copper films is found to increase with the increase in the density of the copper microdots. A critical copper deposition potential of-0.6 V in conjunction with the stearic acid modification provides a surface roughness of 6.2 μm with a water contact angle of 157?, resulting in superhydrophobic properties on the aluminum substrates.
文摘In the phosphate buffer solution of pH＞7,the cysteine sensitized the electrochemiluminescence (ECL) of luminol.It could be modified on the surface of platinum electrode and furthermore adsorbing the luminol on its exterior to construct an ECL sensor.The ECL intensity of this sensor was strong enough and very stable.There wasn't obvious decrease of ECL intensity for thirty times of using in 48 hours with the relative standard deviation (RSD) of 0.98%.It could be used to determine some quenching effective molecules such as superoxide dismutase (SOD) with negative response upon the concentration range from 4.8 IU/ml to 57.6 IU/ml.
文摘In this paper, the content of water glass before and after adding modifying agent was measured by Trimethylsilyl-gas-chromatography. The experimental results showed that different modulus of water glass could generate different content of mono-silicate acid and oligomeric silicate acid in water glass. After a period of storage, different modulus of water glass led to decrease of silicate content at different levels. Because higher content of Na<sub>2</sub>O in water glass tended to incur the alkaline polymerization, the occurrence of depolymerization of silicate species would lead to an increase of oligomeric silicate species, resulting in a drawback of silicate species content after a period of storage. And contrary to that, lower content of Na<sub>2</sub>O in water glass tended to incur the acidic polymerization. When the modifying agent was added to the newly made water glass, the amount of mono-silicate acid and oligomeric silicate acid also decreased. In modified water glass, the change of each silicate acid species was less than that in unmodified water glass. These results showed that the modifying agent retarded the aging of water glass. It had remarkable significance on the theory and practical application of water glass chemistry.
文摘Acylation has been shown to be an effective toolfor improving surface functional properties of plant proteins.Soy bean protein has been extensively modified throughchemical and enzvmatic treatments.Their effectiveness lies intheir high nutritional value and low cost,which promotetheir use as ingredients for the formulation of food products.This paper reports a complete review of chemical modificationof various proteins from plant and animal sources,The nutri-tive and toxicological aspects through in vitro and in vivotests are also described.
文摘A linear a-D-(13)-glucan, named PSG, was obtained from the spores of Ganoderma lucidum. The synthesis of positively and negatively charged polyelectrolytes from PSG was developed. Amine groups and carboxymethyl groups were introduced through nucleophilic substitution with 3-chloropropylamine or chloroacetic acid, respectively. Reaction conditions were varied to obtain insight into the influence of variables on the degree of substitution.
文摘Scrap vulcanized rubber is amongst a bigger waste polymers. It does not decompose easily owing to its cross linked structure. Modification of scrap tires powder by the grafting with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is described. The grafting is achieved through free radical initiation. The effects of different amount of monomer and initiator were examined. Also the influence of reaction time and temperature were investigated. The grafted waste rubber was characterized by FT/IR, SEM and DSC measurements. The proposed mechanism of the grafting reaction is discussed. From DSC and SEM studies of WR-g-AMPS compared with PAMPS and WR, the results show that the particle size and crystallinity were enhanced for the grafted copolymers. The obtained modified scraped tires will used as an ion exchanger for the future applications.
文摘Tryptophan(Trp) residues in a pullulanase were modified by N-bromosuccinimide(NBS). The results of the Spande method indicate that there are 18 Trp residues in the pullulanase and nine of them are located on the surface of the enzyme. Three of these Trp residues are nonessential residues which show the fastest reaction rate according to the Zou′s plot. Two of the seven relative faster reacting residues are essential for the activity of the enzyme. The other eight are the slowest in the reaction rate or non-reactive residues for the reaction. The fluorescence and circular dichroism(CD) spectra of the pullulanase have been changed after the reaction with NBS. Potassium iodide(KI) and acrylamide also have remarkable influences on the fluorescence spectra of the pullulanase.
基金This work was supported by the Young Scientist & Technician Creation Item sponsored by Fujian Province (No. 2002J021)and Scientific Research Fund Sponsored by Huaqiao University.
文摘The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 °C for 30 min in 15 mL 1 % PVA/H2O. Then 4.34 moi/L VAc was added dropwise and the reaction was allowed to proce at 48 °C for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.
基金Project supported by the National Natural Science Foundation of China (20163002)and the Jianxi Natural Science Foundation( 0220004 )
文摘To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium carbonate as raw material was proposed.The effect of modifier reaction percentage, reaction time, calcining temperature and modifier amount on particle size, density, suspensibility, and hardness of compound CeO2 powder was investigated.The phase evolutions of preparation process were characterized by XRD.SEM micrograph of the final product shows that compound CeO2 powders obtained are well-dispersed, spherically-shaped, uniformly-sized and submicron-sized particles.The method is readily available in raw material, low in cost, simple in process, and has great potential for industrialization.The compound CeO2 powders of different physical properties can be synthesized by controlling the above-mentioned influence factors in preparation process.
基金supported by the National Basic Program of China(Grant No.2013CB632101)the National Natural Science Foundation of China(Grant Nos.61222404 and 61474097)the Fundamental Research Funds for the Central Universities of China(Grant No.2014XZZX003-09)
文摘Silicene is a two-dimensional(2D) material, which is composed of a single layer of silicon atoms with sp2–sp3mixed hybridization. The sp2–sp3mixed hybridization renders silicene excellent reactive ability, facilitating the chemical modification of silicene. It has been demonstrated that chemical modification effectively enables the tuning of the properties of silicene. We now review all kinds of chemical modification methods for silicene, including hydrogenation, halogenation,organic surface modification, oxidation, doping and formation of 2D hybrids. The effects of these chemical modification methods on the geometrical, electronic, optical, and magnetic properties of silicene are discussed. The potential applications of chemically modified silicene in a variety of fields such as electronics, optoelectronics, and magnetoelectronics are introduced. We finally envision future work on the chemical modification of silicene for further advancing the development of silicene.
文摘Silk fibers have been grafted with ethylene glycol dimethacrylate (EGDMA) and characteristics of the grafted silk fibers were analyzed in relation to the graft yield on the basis of the tensile properties, dyeing behaviour, durability during laundering and solubility of the specimen in NaOH solution. The amount of the acid dye absorbed by the fibers decreased with increasing graft yield, while the value of rating for washing fastness on silk fibers was almost unchanged by the graft treatment. The breaking loads of the fiber were almost unchanged whereas rigidity of the fibers increased after graft treatment. Graft treatment enhanced silk fiber durability during laundering and in NaOH solution.
文摘Objective: To investigate the effects of acetylation and pregelatinization of cassava and sweet potato starches on the mechanical and release properties of directly compressed paracetamol tablet formulations in comparison with official corn starch.Methods: The native starches were modified by acetylation and pregelatinization. The tablets were assessed using friability(Fr), crushing strength(Cs), disintegration time(Dt) and dissolution parameters. Results: Starch acetylation produced paracetamol tablets that were stronger and had the best balance of mechanical and disintegration properties, while pregelatinization produced tablets that were more friable but had a better overall strength in relation to disintegration than formulations made from natural starches. Correlations mainly existed between Dt and the dissolution parameters t80, t2 and k1 in the formulations. Conclusions: Modification of the experimental starches improved the mechanical and release properties of directly compressed paracetamol tablet formulations. Thus, they can be developed for use as pharmaceutical excipients in specific formulations.
基金The Hi-tech Research and Development Program of China(2002AA2Z3318)Guangdong Natural Science Foundation(010424)supported this study.
文摘A new product PEGylated rhaFGF was obtained by site-directed chemical modification. When compared with unmodified rhaFGF, PEGylated rhaFGF showed comparable bioactivity and superior stability at 37°C in mouse serum and the stronger resistant potency to trypsin. This was accompanied by a substantial decreasing immunogenicity. Site-specific PEGylation of rhaFGF may increase its therapeutic potency in humans.
文摘Tryptophan(Trp)residues in pullulanase have been chemically modified with N-bromo- ssuccinimide(NBS). The results of ultraviolet spectra indicated that there are 18 Trp residues in pullulanase and nine of them are located on the surface of the enzyme. Three of these Trp residues are none-essential residues which showed the fastest reaction speed by Zhou’s plot. Two of the seven relative faster reacting residues are essential for the activity of the enzyme. The other eight are none-reactive residues with lowest reaction speed.
文摘Bio-based nanomaterial is more attractive, due to its abundance, eco-friendliness and sustainability, when compared to the non-renewable toxic petrochemicals used in the wood adhesive sector. Recent studies on the formaldehyde emission by petrochemical binders in wood adhesives have attracted scientists for the research in biomaterial-based binders. In this aspect nanocellulose (NC) is one such material which has reinforcing ability and has natural binding properties. Conventional wood adhesive uses petrochemical-based binders and additives. Inclusion of nanocellulose in wood adhesive could drastically reduce the dependency on non-renewable petroleum sources. Even though wood adhesive uses NC for improving mechanical properties of the adhesive, usage is restricted because of its inability to enhance tackiness and adhesion compared with petrochemicals. Availability of free hydroxyl groups and feasibility for modification can be a potential way for functionalization of this nanomaterial. To improve adhesion properties and to make nanocellulose act as a functional filler, the crosslinking approach can be a possible solution. Enhancement of thermal properties with improved thermal degradation, water barrier properties of crosslinked films and enhanced mechanical properties especially in crosslinked poly (vinyl alcohol) (PVA) matrix, which is one of the binders for wood adhesive discussed in this review paper proves the potential applicability of crosslinked NC. Hence by inclusion of NC in wood adhesive and crosslinking with the binder, both mechanical and performance properties are expected to enhance which will create a new world and possibilities for the bio-based eco-friendly wood adhesives. In this review paper, we have reviewed the crosslinking of nanocellulose to enhance the performance of wood adhesives.
文摘Acetylacetone was firstly introduced into the aqueous media with the presence of aluminum sec-butoxide and peptizator. It was confirmed that the UV (ultraviolet) absorption band of acetylacetone underwent 14 nm of red-shift due to the formation of the six-membered ring of the complex between alumina and acetylacetone in the aqueous solution. It was also found that the chemical modification can be dissociated by the UV irradiation with a wavelength shorter than 286 nm as a result of the excitation of π-π* transition in the complex.
文摘The amino acid composition of the superoxide dismutase(SOD) from camellia pollen was measured and the tryptophan(Trp) residues were modified by using N-bromosuccinimide(NBS). The results show that there are 21 Trp residues in an SOD molecule and seven of which are located on the surface of the enzyme. By researching the fluorescence spectra of the native SOD and the modified SOD, we have found that the emission wavelength of Trp is at 335 nm and the fluorescence intensity will decrease when the enzyme is modified. The results also show that potassium iodide(KI) can significantly quench the fluorescence of the native SOD, but it has a less pronounced effect on the modified enzyme. Glycerin as a surface activation reagent can stabilize the fluorescence of the modified enzyme.
