Vietnam Academy of Science and Technology: Journals Online
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EFFECT OF 0.5 AT.% INDIUM ON THERMOELECTRIC PROPERTIES OF GALLIUM DOPED-ZINC OXIDE BULK
No full textThermoelectrics (TE) is well-known as a non-smoke technology for electricity production from waste heat and for greenhouse effect reduction. Enhancing power factor (PF = S2sigma, where S is Seebeck coefficient and sigma is electrical conductivity) and figure of merit of TE materials to achieve high-performance TE devices has attracted much scientific attention. Doping foreign elements into host bulk structure is a basic and traditional solution to modify the thermoelectric properties of materials. In this work, we use small amount of 0.5 at.% In as dopant which is incorporated into Ga-doped ZnO (GZO) bulk by using solid-state reaction method. The effects of In addition on electrical and thermoelectric characterizations of Ga-doped ZnO bulk are discussed in detail. As a result, the electrical conductivity of the IGZO bulk increases more than 20% as compared to the GZO bulk. The Seebeck coefficient decreases insignificantly, which leads to enhancing power factor by 55% from 184.4 uW/mK2 (GZO) to 285.2 uW/mK2 (IGZO) at 500oC. The results open possibility to enhance the figure of merit of pure and doped ZnO material
Forming active recombinant enterokinase expressed in Escherichia coli
No full textEnterokinase is a serine protease commonly used in some biotechnology researches. For these purposes, the light chain containing enterokinase activity has usually been expressed as recombinant protein in different expression systems because natural enterokinase extraction is often ineffective. In this study, we examined the formation of recombinant enterokinase expressed in Escherichia coli with biological activity. The thioredoxin-enterokinase (trx-ent) fusion protein was autocleavaged into thioredoxin and enterokinase when expressed under insoluble form, denatured with guanidine and then refolded with suitable oxidation and reduction steps. Meanwhile, soluble expression as well as insoluble form denatured by urea had not enzymatic activity. Denaturant solution of 6 M guanidine along with the re-folding conditions in oxidized glutathione oxidation buffers followed by the reduced glutathione buffer with arginine was applied to produce trx-ent protein capable of self-cleavage. The recombinant light-chain enterokinase protein had a size of about 35 kDa on the Tris-glycine gel. Initial assessment on substance had shown that enterokinase was capable of cleaving thioredoxin-sumoprotease into thioredoxin and sumoprotease. This result provides the base for the production of active recombinant enterokinase to be used in recombinant protein expression technology
Nonlinear Double-arm Optical Tweezers for Controlling 3D Microspheres
No full textIn this paper, a new nonlinear double-arm optical tweezer combining Mach-Zenhder interferometer, objective lens and organic dye layer is proposed. Based on the ray-optical and wave optical approximations, the expression describing the separation of two trap centers and laser intensity distribution is derived. The obtained results show that the separation between two trap centers, the laser intensity distribution, trap region's area and optical trap efficiency can be controlled by tuning laser power. The proposed model is seen to be a double-arm optical tweezer for controlling 3D microsphere by optical method
Cloning and expression of maltooligosyltrehalose trehalohydrolase from Sulfolobus solfataricus DSM 1616 in Bacillus subtilis WB800
No full textMaltooligosyltrehalose trehalohydrolase (MTHase) is an industrial enzyme for the production of trehalose. A DNA fragment of 1680 bp encoding for MTHase was cloned from Sulfobolus solfataricus DSM 1616 then fused with promoter acoA-amyE already amplified from pMSE3 vector by PCR to generate an expression cassette acoMTH. Afterward the cassette was inserted into pAC7 vector for expression of the gene in Bacillus subtilis WB800 – a conventional expression system. Gene MTH was inserted into the genome of B. subtilis WB800 by cross-exchange event of pAC7 vector with the host genome for expression of high quality and high quantity of extracellular recombinant protein. By crossing-exchange event at 3’amyE-5’amyE, the expressional cassette was integrated into B. subtilis WB800 genome. The expressional cassette was integrated into B. subtilis WB800 genome replacing 3’amyE-5’amyE, hindering the native amylase activity of the host. Expression of expected protein was confirmed by electrophoresis SDS-PAGE. From our results, it indicates that gene MTH was expressed successfully in B. subtilis WB800. After 0.5% acetoin induction for 48 h, the data showed that the protein with a molecular mass of ~64 kDa on SDS-PAGE was expressed. The level of recombinant protein in WBpAacoMTH was increased and reached 2.5%, 15.2% and 21.95%, respectively comparing with native B. subtilis WB800
Prediction of cellulolytic and hemicellulolytic bacterial diversity in the gut of Coptotermes gestroi in the Southern Vietnam
No full textIn lower termite such as Coptotermes gestroi, cellulose and hemicellulose are hydrolysed by cellulases and hemicellulases secreted from bacteria, archaea, protozoa and fungy in the hindgut. In which, majority of the enzymes are contributed by protozoa. From the metagenomic DNA data (125,423 open reading frames -ORFs) of free-living bacteria in the gut of C. gestroi harvested in Southern Vietnam and by MEGA 4.0 software, 100.340 ORFs were classified into 1,368 species, 628 genera, 217 families, 97 orders, 41 classes and 22 phyla (Do et al., 2014). Among these, 2,131 ORFs (2,12%) belong to 24 bacterial species (account 1,75% bacterial species), 11 families, 9 orders, 8 classes and 5 phyla were predicted have ability to produce cellulases; 679 ORFs belong to 18 bacterial species 8 families, 6 orders, 5 classes, 4 phyla were predicted have ability to produce hemicellulase. Majority of cellulase producers were species which of Firmicutes (15/24 species), accumulated in class Clostridia, order Clostridiales. The most abundant cellulase producer was Pseudomonas fluorescens (1,258 ORFs) of order Pseudomonadaceae. Out of the 18 hemicellulase producers, the most abundant species was Clostridium thermocellum (113 ORFs) in the phylum Firmicutes, followed by 3 species belonging to the phylum Bacteroidetes. The species predicted to produce both cellulase, hemicellulase were C. thermocellum, Ruminococcusns flavefaciens and Bacillus subtilis. Our study provides a data of gut cellulose and hemicellulose - degrading bacteria composition of C. gestro
Detection of protein stoichiometric phosphorylation using Phos-tag SDS-PAGE
No full textProtein phosphorylation plays an important role in many cellular signalings which are relating to many diseases. Therefore, a variety of biochemical techniques has been developed to study protein phosphorylation in cells. Protein phosphorylation has traditionally been detected by radioisotope phosphate labeling of proteins with radioactive ATP. Phosphorylation site-specific antibodies are now available for the analysis of phosphorylation status at target sites. However, these antibodies cannot be used to detect unidentified phosphorylation sites. Recently, the Phos-tag technology has been developed to overcome the disadvantages and limitations of these methods. Phos-tag and its derivatives conjugated to biotin, acrylamide, or agarose, and can capture phosphate monoester dianions bound to serine, threonine, and tyrosine residues, in an amino acid sequence-independent manner. The grouping of the Phos-tag will alter the mobility of protein on the gel depending on the amount of serine, threonine or tyrosine which are phosphorylated. Here, we describe the method to detect the phosphorylation of Pop2 protein, one of the exonucleases in the Ccr4-Not complex regulating the shortening of poly(A) tail of mRNAs using phosphate affinity Phos-tag SDS-PAGE. We observed clear electrophoretic 04 shift bands of Pop2-3XFlag under unstressed conditions. This is the first study which observes Pop2 phosphorylation in normal culture conditions. This study showed the convenience and advantages of Phos-tag SDS-PAGE for research on molecular mechanisms regulating the function of protein
Cloning of sucrose isomerase encoding gene from Klebsiella singaporensis ISB-36 and its expression in Pichia pastoris
No full textGiven potential health benefits including low glycemic index, tooth friendly, suitable to infants, elderly and diabetic patients, isomaltulose was considered as a promising alternative sweetener to sucrose. Due to the presence of liposaccharide endotoxin in Serratia plymuthica CBS 574.44, a Gram-negative bacterium, and minute amount of formaldehyde carried over, purification of isomaltulose requires rigorous controls in industry. To reduce the cost associated with product purification, here we propose the use of recombinant enzyme in isomaltulose production. The mature gene coding for sucrose isomerase synthase (K.SI36.PalI) from Klebsiella singarporensis ISB 36, which isolated from woodborer in Vietnam, was expressed in Pichia pastoris X33. The nucleotide sequence of K.SI36.PalI gene was similar to AY040843.1 of Klebsiella sp. LX3 except one nucleotide C1025 in AY040843.1 replaced by T1025 in K.SI36.PalI. This leads to single amino acid difference in deduced protein sequence (from 342Ser to 342Phe). Furthermore, the addition of two amino acids (Glu and Phe) was observed at N-terminus. The calculated molecular weight of sucrose isomerase from K.SI36.PalI was 67.46 kDa and the pI was 6.55. There was one potential glycosylation site at 466Asn. The maximum sucrose isomerase activity in the culture broth reached 36,6 U.mL-1in 1 L shake-flask. The purified recombinant enzyme was most active at 40°C and pH 7.0. At the optimum condition, within 6 hours, the enzyme converted 94% of sucrose in a 40% sucrose solution into isomaltulose. This was the first study on the expression of sucrose isomerase synthase gene in P. pastoris, and the results showed the efficient conversion of sucrose isomerase recombinant
Caffeine improves the developmental competence of parthenogenetic embryos derived from aging porcine oocytes
No full textOocytes are committed to deterioration in quality as they aged due to a long duration manipulation which leads to the reduced success rate of somatic cell nuclear transfer (SCNT). Caffeine with an effect to maintain the maturation-promoting factor (MPF) from the metaphase of oocytes is expected to enhance the quality of the aging oocytes. To investigate the timely treatment of caffeine to rescue aging oocytes, caffeine was supplemented after in vitro maturation (IVM) or during metaphase I – metaphase II (MI – MII) transition. First, the effect of caffeine after IVM of oocytes was examined. After IVM for 42 h, oocytes were left for aging within 6 or 8 hours in supplement with various concentrations of caffeine (0, 5 and 10 mM), and then, examined the quality of embryo from aged oocyte through parthenogenesis activation. We found that 5 mM caffeine for the first 6 hours of aging process was suggested to improve the early development of parthenogenetic diploid embryos. However, the cytoplasmic homogeneity is significantly reduced in aging oocyte compared to fresh oocyte and it could not be improved by caffeine treatment. Next, the effect of caffeine during MI – MII transition of oocyte was examined. Caffeine was supplemented during MI – MII transition (27 – 42 h) of IVM. Then mature oocytes were left for aging within 6 h to examine on aging porcine oocyte quality via parthenogenesis embryos. The results indicated that 5 mM caffeine during MI-MII transition could efficiently rescue aged oocytes and improve the development of embryos derived from aging oocytes to four-cell, eight-cell and blastocyst stage as compared to fresh oocytes. Especially, these aged oocytes treated by caffeine could improve the cytoplasmic homogeneity in embryos and the quality of blastocysts by increasing cell number similar to fresh oocytes
A contribution to the establishment of extract standards from the leaves of Clinacanthus nutans (Burm.f.) Lindau
No full textNowadays, herbs have become a popular form of healthcare. Clinacanthus nutans (Burm.f.) Lindau (family Acanthaceae) is popular in Asia, especially in the tropical countries. Extracts of C. nutans leaves are widely used to treat diseases of skin, anti-inflammatory, anti-virus, anticancer, antioxidant, antidiabetic, immunomodulatory, wound healing and analgesic activities, etc. This study determined the parameters of ethanol extract of C. nutans leaves including pH, total weight loss due to water, total ash content, heavy metal content, microbiological limits, pesticide residual content, presence and contents of C-flavones. The C-flavones such as shaftoside, orientin, isovitexin and vitexin have been found to be major flavonoids in the leaves of this plant. Therefore, we had used a two-step method using thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) for the rapid identification and quantification of the flavones C-glycosides in ethanol extract C. nutans leaves. These results provided useful information for the evaluation of quality of C. nutans raw materials and its commercial products. Moreover, that contributed to the establishment of extract standard from the leaves of C. nutans. The parameters of the ethanol extract of C. nutans leaves were obtained as follows: pH (5,23 ± 0,35), total weight loss due to water (15,62 ± 0,25%), total ash (13,85 ± 0,98%), microbiological limits are achieved the requirement of medicinal standards, content heavy metal and residue of pesticide are not detected. Contents of C-flavones: shaftoside (0,69 ± 0,04 mg/g), orientin (0,24 ± 0,008 mg/g), isovitexin (0,015 ± 0,003 mg/g), vitexin were very low or undetectable
SURVEY ON THE CONCENTRATION OF RADON (222Rn) AND RADIUM (226Ra) IN DOMESTIC WATER IN BAC TU LIEM DISTRICT, HANOI CITY
No full textRadon (222Rn) and Radium (226Ra) are natural radiation isotopes that greatly affect human health. Based on that study, we surveyed the 222Rn and 226Ra concentration in domestic water, including: 12 samples of supply water, 18 samples of treated well water and 30 samples of well water in households in the area of Bac Tu Liem District, Hanoi City. Radon gas concentration is determined by a specialized measuring device, RAD-7 and Radium gas concentration is determined by Radium adsorption method on MnO2 plate. The results of the study showed that the radium concentration in the survey area had 07 samples of treated well water with concentration from ~ 1.03 to ~ 1.27 times higher than the allowed limit. The radon concentration in supply water is from (0.05 ± 0.02) Bq.l-1 to (1.05 ± 0.04) Bq.l-1; Well treated water is worth (0.8 ± 0.03) Bq.l-1 to (3.56 ± 0.08) Bq.l-1 and bore well water has values ranging from (1.67 ± 0.08) Bq.l-1 to (8.87 ± 0.23) Bq.l-1, these values are within the limits allowed by the Environmental Protection Agency (EPA) is 0.185 Bq.l-1. Samples of well water concentration of 222Rn, 226Ra are higher than those of tap water and treated water. In addition, concentrations of 222Rn and 226Ra in the surveyed sources have no linear relationship