Production of high-purity recombinant human vascular endothelial growth factor (rhVEGF165) by Pichia pastoris / 生物工程学报

Vascular endothelial growth factor (VEGF165) is a highly specific vascular endothelial growth factor that can be used to treat many cardiovascular diseases. The development of anti-tumor drugs and disease detection reagents requires highly pure VEGF165 (at least 95% purity). To date, the methods for heterologous expression and purification of VEGF165 require multiple purification steps, but the product purity remains to be low. In this study, we optimized the codons of the human VEGF165 gene (vegf165) according to the yeast codon preference. Based on the Pichia pastoris BBPB vector, we used the Biobrick method to construct a five-copy rhVEGF165 recombinant expression vector using Pgap as the promoter. In addition, a histidine tag was added to the vector. Facilitated by the His tag and the heparin-binding domain of VEGF165, we were able to obtain highly pure rhVEGF165 (purity > 98%) protein using two-step affinity chromatography. The purified rhVEGF165 was biologically active, and reached a concentration of 0.45 mg/mL. The new design of the expression vector enables production of active and highly pure rhVEGF165 ) in a simplified purification process, the purity of the biologically active natural VEGF165 reached the highest reported to date.

An experimental study of the effect of extraction and retention of canine primary intruded teeth to the permanent successors / 中华口腔医学杂志

Objective@#To compare the influence of extraction and retention of the intruded dogs' teeth on permanent successors.@*Methods@#Nine healthy 45-days-old Chinese rural puppies were selected, and six were submitted to the intrusion of the bilateral canine. Intruded teeth on the left side were extracted 30 minutes later and the teeth on the right side were kept in their sockets. After 8 months, all dogs were sacrificed. General observation, periapical radiograph and cone beam CT were used to observe the preoperative and postoperative deciduous teeth, permanent germs and permanent teeth development. The structure and content of successors' enamel were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).@*Results@#In the extraction groups, the enamel hypoplasia was found in 19 permanent successors, ectopic eruption in 2 cases and abnormal teeth were in 19 cases in total (79%). In the retention groups, enamel hypoplasia of the permanent successors occurred in 2 cases, root dilaceration in 6 cases, and ectopic eruption in 5 cases, retained deciduous teeth in 3 cases, and there were 22 abnormal teeth in total (92%). In blank control group, there was no abnormal teeth. The major effect of intruded deciduous teeth on the permanent successors exhibited enamel hypoplasia [85% (41/48)], presented as enamel coloration and enamel defect (P=0.416).@*Conclusions@#The intruded deciduous teeth should be removed early in order to reduce the effect on the permanent teeth.

Animal experimental study of tooth transplantation into artificial tooth socket / 实用口腔医学杂志

Objective: To observe morphological change and diversity of periodontium and alveolar bone after tooth transplantation into artificial tooth socket. Methods: 6 dogs were divided randomly into 2 groups: 2 dogs were used as the controls and 4 used for the experiment. In the control group 4 teeth were autotransplanted into the inherent sockets. In the experiment group 4 teeth were autotransplanted into the artificial sockets. The dogs were sacrificed at the 16th week after operation. The healing condition of periodontal tissue and the remodeling of alveolar bone were examined. Results: None of the transplanted teeth in both groups was loosen or dropped. Mircro-CT examination showed that cancellous bone and bone trabecula around the transplanted teeth lined tightly,no significant difference of bone trabecula thickness was observed between the 2 groups. Hard tissue slice examination revealed that parodontium of both groups grew and adhered to the teeth,and the quantity of new-born bone between the top of alveolar ridge and the neck of transplanted teeth was fundamentally the same in the 2 groups. Conclusion: Autotransplantation of teeth into the artificial socket is similar to that into inherent socket.

Covalent immobilization of glucose oxidase within organic media / 生物工程学报

Activity losing during the covalent immobilization of enzyme is a serious problem. Here we studied organic phase immobilization by using glucose oxidase (GOD) as a model. After lyophilized at optimum pH, GOD is covalently immobilized onto glutaraldhyde-activated chitosan microsphere carrier under the condition of water, 1, 4-dioxane, ether and ethanol separately. The special activities, enzyme characterization and kinetic parameters are determined. Results show that all of the organic phase immobilized GODs have higher special activities and larger K(cat) than that of aqueous phase. Under the conditions of 0.1% of glutaraldehyde, 1.6% moisture content with 80 mg of GOD added to per gram of carrier, 2.9-fold of the special activity and 3-fold of the effective activity recovery ratio were obtained, and 3-fold of the residue activity was demonstrated after 7 runs when compares 1, 4-dioxane phase immobilized GOD with water phase immobilized one. In addition, kinetic study shows that 1,4-dioxane immobilized GOD (Km(app) = 5.63 mmol/L, V(max) = 1.70 micromol/(min x mg GOD), K(cat) = 0.304 s(-1) was superior to water immobilized GOD (Km(app) = 7.33 mmol/L, V(max) = 1.02 micromol/(min x mg GOD), K(cat) = 0.221 s(-1)). All above indicated GOD immobilized in proper organic media presented a better activity with improved catalytic performance. Organic phase immobilization might be one of the ways to overcome the conformational denature of enzyme protein during covalent modification.

Directed evolution of aflatoxin detoxifzyme in vitro by error-prone PCR / 生物工程学报

The experiment was conducted by directed evolution strategy (error-prone PCR) to improve the activity of aflatoxin detoxifzyme with the high-throughput horse radish peroxidas and recessive brilliant green (HRP-RBG) screening system. We built up a mutant library to the order of 10(4). Two rounds of EP-PCR and HRP-RBG screening were used to obtain three optimum mutant strains A1773, A1476 and A2863. We found that mutant A1773 had upper temperature tolerance of 70 degrees C and that its enzyme activity was 6.5 times higher than that of the parent strain. Mutant strains A1476 worked well at pH 4.0 and its enzyme activity was 21 times higher than that of the parent strain. Mutant A2863 worked well at pH 4.0 and pH 7.5, and its enzyme activity was 12.6 times higher than that of the parent strain. With DNA sequencing we found that mutant A1773 revealed two amino acid substitutions, Glu127Lys and Gln613Arg. Mutant A1476 revealed four amino acid substitutions: Ser46Pro, Lys221Gln, Ile307Leu and Asn471lle. Mutant A2863 revealed four amino acid substitutions: Gly73Ser, Ile307Leu, Va1596Ala and Gln613Arg. The results provided a useful illustration for the deep understanding of the relationship between the function and structure of aflatoxin detoxifzyme.

Directed evolution by error-prone PCR of Armillariella tabescens MAN47 beta-mannanase gene toward enhanced thermal resistance / 生物工程学报

Firstly, We used error-prone PCR to induce mutations on Armillariella tabescens MAN47 beta-mannanase gene, Secondly, we cloned the mutated fragments into secreted expression vector pYCalpha, Then the recombinant plasmids were transformed into Saccharomyces cerevisiae BJ5465 after amplified and extracted in DH5alpha cells. Through three cycles of error-prone PCR we built a mutant database, Then we screened one optimum (named M262) from about 104 mutants. The evoluted MAN47 beta-mannanase displayed both higher thermal stability and activity than wide type. The evoluted enzyme M262 retained high activity after treatment at 80 degrees C for 30 min, whereas, the wild type nearly lost activity under this condition. Meanwhile, the activity of M262 can reach to 25 U/mL, which is 4.3 times as wide type under optimum temperature. In addition, pH stability and pH range of evoluted enzyme M262 were both improved compared with wild-type enzyme. The optimum pH was estimated to be similar to that of wild-type enzyme. The sequence comparison illustrated that there were three nucleotide substitutions (T343A/C827T/T1139C) which carried corresponding amino acid changes (Ser115Thr/Thr276Met/Val380Ala). According to homologous modeling by SWISS-MODEL Repository, three mutated amino acids located at the sixth amino acid of the fourth beta-sheet, the first amino acid of the sixth alpha-helix, the turn between the tenth and eleventh beta-sheet, respectively.

Investigation of micro-aqueous covalent immobilization of horseradish peroxidase by "conformation memory" / 生物工程学报

We has studied the feasibility of preventing protein from denature during covalent immobilization by "conformation memory", which was achieved by freeze-drying under enzyme active conformation and cross-linked with carrier under micro-aqueous media (MAM). Horseradish peroxidase (HRP) and chitosan beads have been used as the model enzyme and carrier. The MAM consisted of 99% dioxane and 1% water. We compared the immobilized HRP under MAM with that under traditional aqueous solvent, found that the optimum temperature of both was raised to 60 degrees C, and the optimum pH was 6.5. However, the MAM-immobilized HRP had shown less activity loss during usage and six times higher activity than that immobilized under aqueous solvent. After 30 min incubation at 70 degrees C, the MAM-immobilized HRP remained 75.42% activity while the aqueous-media-immobilized enzyme only 15.4%. The MAM-immobilized HRP has shown a better operation stability with 77.69% residue activity after 5 times of repeat operation while the aqueous-media-immobilized enzyme only 16.67%. In addition, the MAM-immobilized HRP had also shown more advantages when used in phenol removal. We constructed enzyme electrodes (CS-HRP-SWCNTs/Au) to further display the different properties of the two immobilized HRP. MAM-immobilized HRP-electrode has shown two times stronger response signal to H2O2 than that immobilized under aqueous media, which indicated a better enzyme activity of MAM-immobilized HRP. Our research demonstrated that the conformation memory, to some extent, did contribute to preventing protein from denaturing when use HRP as a model, and it is feasible to immobilize enzyme by covalent cross-linking method under micro-aqueous media.

Detection of sterigmatocystin based on the novel aflatoxin-oxidase/chitosan-single-walled carbon nanotubes/poly-o-phenylenediamine modified electrode / 生物工程学报

A sensitive electrochemical biosensor based on Aflatoxin-Oxidase (AFO) was developed for detection of sterigmatocystin (ST). The enzyme was immobilized on chitosan-single-walled carbon nanotubes (CS-SWCNTs) hybrid film, which attached to the poly-o-phenylenediamine (POPD)-modified Au electrode. The fabricated procedures of the biosensor were characterized with atomic force microscopy (AFM), fourier transform-infrared spectroscopy (FT-IR), and electrochemical impedance spectroscopy (EIS). The cyclic voltammetric results of the biosensor indicated that AFO exhibited a surface-controlled and quasi-reversible electrochemical redox behavior with a formal potential of -0.436 V (vs. Ag/AgCl) in 0.1 mol/L PBS (pH 7.0), which resulted from the direct electron transfer between entrapped AFO and the underlying electrode. The enzymatic electrode exhibited an excellent electrocatalytic response to ST. The linear range of ST determination was from 10 ng/mL to 310 ng/mL with correlation coefficient of 0.997, the detection limit was 3 ng/mL (S/N=3), and the response time was less than 10 seconds. The apparent Michaelis-Menten constant (K(M)app) was estimated to be 7.13 micromol/L. The biosensor had the advantages of good repeatability and stability, remaining 85.6% of its original current value after storage at 4 degrees C for a month, and the RSD for 11 replicate determination of 20 ng/mL ST was 3.9%. This AFO/CS-SWCNTs/POPD/Au modified electrode showed high selectivity and sensitivity in real sample analysis, giving values of recovery in the range of 87.6%-105.5%. The proposed method can be applied to the determination of ST in real samples with satisfactory results.

Cloning, expression and characterization of mannanase from Armillariella tabescens EJLY2098 in Pichia pastoris / 生物工程学报

We used reverse transcriptase polymerase chain reaction (RT-PCR) and rapid amplification of cDNA end (RACE) techniques to obtain the full-length cDNA of beta-mannanase (EC 3.2.1.78) from Armillariella tabescens EJLY2098 (an edible fungus). Sequence analysis of the 1481 bp full-length cDNA encoding 445 amino acid residues indicated that the gene contained two structural domains, cellulose-binding domains (CBD) and glycoside hydrolase family 5 (GHF5) domains, other than the conserved beta-mannanase domain. Thus, we classified this gene as a member of glycoside hydrolase family 5. Next, we cloned a 1308 bp fragment encoding the beta-mannanase mature peptide (re-atMAN47) into the expression vector pPICZalphaA and expressed it in Pichia pastoris. The yield was 440 mg/L. Enzyme activity reached a maximum of 1.067 IU/mL after 72 h of methanol induction. The re-atMAN47 had an optimal temperature of 60 degrees C and an optimal pH of 5.5. It manifested broad thermostability from 30 degrees C-65 degrees C, and was stable between pH 4.5-7.0. This study represents the first record of a beta-mannanase from Armillariella tabescens EJLY2098 and provides a new source of carbohydrate hydrolysis enzyme with good biosafety, thermostability and wide pH stability. It is a good approach for the industrial needs of feed, food and pharmaceutical manufacturers.

The Assembly of a Novel Enzyme Biosensor for Aflatoxin B1 Detection / 中国生物工程杂志

A novel biosensor for aflatoxin B1 detecting has been reported. The biosensor electrode for AFB1 detecting was assembled by immobilized aflatoxin-oxidoreductase using open-ended multi-walled carbon nanotubes as matrix. Its linear range was between 0.16μM and 3.2μM. And if the specific anti-aflatoxin B1 antibody and aflatoxin oxidoreductase were both immobilized on the electrode with Multi-Walled carbon nanotubes, the detection limit of the modified electrode could be 16 nM with a 10 times improved sensitivity. The aflatoxin enzyme biosensor assembled this way strode one step forward its practical application.

Construction and Determination of an Episomal Secreting Expression Vector:pYES2/CT/?-factor for Saccharomyces cerevisiae / 中国生物工程杂志

pPIC9 was used as a template and ?-factor gene of Saccharomyces cerevisiae was amplified by PCR.The gene was cloned in the intracellular expression vector pYES2/CT for Saccharomyces cerevisiae and the secreting expression vector named pYES2/CT/?-factor(pYC?)was constructed.The gene of mannase(man)from recombinant vector of pKLAC1-man(pKLman) was cut by restriction enzymes and linked with pYC?.This recombinant vector pYC?-man was used to determine the secretory ability and stability of pYC?.The excellent secretory ability of pYC? was proved by two experiments.One showed that INVSc1/pYC?-man clones formed the clear rings around the clones on the medium contained trypan blue,while INVSc1/pYC? clones had no rings.Further analysis of mannase activity of extracellular supernatant and intracellular extracts showed that both extracellular and intracellular mannase activities of INVSc1/pYC? were not detected,while INVSc1/pYC?-man had evident extracellular mannase activities and no intracellular mannase activities.The stability of pYC? was also very good proved by continuous cultivation for about 150h.

Construction of a cDNA Library and Cloning of an Arabinosidase cDNA from Armillariella tabescens / 中国生物工程杂志

The expression cDNA library of A. tabescens was constructed by SMART technique, which useλTriplEx2 as a vector. The titer and the percentage of the constructed library were about 1.0 × 106pfu/mland 98.3% respectively, and the titer and the capacity of the amplified library were about 3.1 × 108pfu/mland 4.2 × 1010. The library was used to provide expressed sequence tags (ESTs). 147 Expressed SequenceTaqs (ESTs) were gained from 176 clones, which were selected randomly and sequenced at the 5'end. Thesequences were submitted to the EMBL database. Blasting the sequences in the GenBank, 43 of them werefound that they have significant similarity with data in GenBank. EST AJ620046 was has significantsimilarity with the arabinosidase of Bacteroides thetaiotaomicron. Using SMART-RACE a full-length cDNA ofAJ620046 was successfully obtained. In order to initially characterize the biochemical properties ofAJ620046, the ORF of AJ620046 named AF was cloned and expressed in Pichia Pastoris yeast.Recombinant pHIL-S1-AF constructed by inserting AF into pHIL-S1 was transformed into Pichia PastorisGS115. Preliminary experiments indicated that AJ620046 was expressed as a 32 kDa protein in recombinantyeast.

The role of tumor necrosis factor alpha in the pathogenesis of immunologically mediated aplastic anemia in mice / 中国病理生理杂志

The plasma levels of TNF alpha was determined dynamically using TNF ELISA; and TNF mRNA in spleen cells from varied groups was determined using Northern Blot. The results showed that: (1) Elevated levels of TNF-alpha in plasma from mice of immunologically- mediated aplastic anemia. (2) Induced production of TNF from spleen cells were much lower in exprimental groups than that in normal control group. (3) Decreased TNF-? gene expression present in spleen cell in AA group compared with normal control group.