Mutation induction of Pleurotus ferulae by low-energy N^+ ion implantation and characters of the selected mutant

In order to obtain Pleurotus ferulae with high temperature tolerance, mycelium mono-cells of wild type strain ACK was treated by nitrogen ion (5~30 keV, 1.5×1015~1.5×1016 cm-2) implantation, and mutant CGMCC1762 was selected through auxotrophy screening method, which was Lys, VB6 auxotrophy stress with high temperature. We found that during riper period the surface layer mycelium of the mutant was not aging neither grew tegument even above 30°C. The mycelium endurable temperature of the mutant was increased 7°C compared with that of the wild type strain. The fruiting bodies growth temperature of the mutant was 16~20°C in daytime and was 6~12°C at night. The highest growth temperature of fruiting bodies of the mutant was increased by 5°C than that of original strain. Through three generation investigation, we found that the mutant CGMCC1762 was stable with high temperature tolerance.

Synthesis of a New Rigid Bicyclic AMPP Ligand (TIAMPP) and Application in Asymmetric Hydrogenation

The new rigid bicyclic AMPP（（S）-TIAMPP） has been synthesized from the corresponding Ticol and Ph2PCI. The application of （S）-TIAMPP in Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acids derivatives has been examined. Up to 93% ee was obtained.

Purification and Biochemical Characterization of D-hydantoinase and D-N-carbamoylase from Burkholderia cepecia.njut01

Hydantoinase and N-carbamoylase play important rol es in the production of optically pure amino acids from racemic 5-monosubstitut ed hydantoins. In this report, hydantoinase and the N-carbamoylase from Burkh olderia cepecia.njut01 were purified to homogeneity by chromatography (Pharma cia Explorer 100 system). The substrate specificity, enantioselectivity, pH depe ndence of activity and temperature stability of the activity were characterized. The results show that the hydantoinase and N-carbamoylase induced from Burkh olderia cepecia.njut01 are both strict D-stereo selective enzymes. They both hydrolyze substrates with side chains containing aliphatic and aromatic res idues with higher activity and affinity toward aromatic than aliphatic substitu ted substrates. The hydantoinase is a homotetramer with subunit molecular weight near 52,000 and is active between pH 6.5 and 10 with an optimum near pH 9.0. The en zyme is active at temperatures up to 60°C, however,it appears instable at h ig her temperatures. The subunit molecular weight of N-carbamoylase is about 35KD. The N-carbamoylase is active in the pH range from 6.0 to 9.5. The optim-pH is 7.2 and the optimizing bioconversion temperature of the N-carbamyolase is 52 °C.

Synthesis of New Ligand 1,2-Bis{di[(R,R)-1,3,2-oxzaphosphlidine]phosphino}ethane with C_2-symmetric Axis and Application in Rh-catalyzed Asymmetric Hydrogenation

New ligand 1,2-bis{di[（R,R）-1,3,2-oxzaphosphlidine]phosphino}ethane [（R,R）-BDOPPEs 1,2,3 and 4] with C2-symmetric axis and bearing nitrogen and oxygen were synthesized from readily available optically active amino alcohols.Rh complexes with these ligands were highly enantioselective catalysts for asymmetric hydrogenation of N-benzoyldehydroamino acid derivatives and α-functionalized ketones in 99%e.e.and 98%e.e.,respectively.This new class of（R,R）-BDOPPEs 1,2,3 and 4 gave much more effectivity and enantionselectivity than their corresponding non-C2-asymmetric aminophosphine phosphinite.

KNaY-zeolite catalyzed dehydration of methyl lactate

A promising catalyst, KNaY was prepared by an ion exchange method with aqueous potassium chloride solution, Compared with NaY, KNaY was an effective catalyst for the dehydration of methyl lactate to methyl acrylate. Under the optimized conditions, an improved yield of 37.9 mol% was achieved.

Effects of Doping CeO_2,Er_2O_3 on Properties of TiO_2-SiO_2 Ceramics for Catalyst Supporter of deNO_x

Effects of doping CeO2 and Er2O3 on the mechanical strength, thermal expansion coefficient, sintering temperature of TiO2-SiO2 ceramics were investigated. The experimental results and the microscopic analysis of SEM, XRD, TG-DSC, FT-IR and TEM show that adding CeO2 and Er2O3 into TiO2-SiO2 ceramics can prohibit the growth of its crystal grains, make their size uniform and form them into a dense structure, which finally enhance its mechanical behaviors, and the lower thermal expansion coefficient that leads to an excellent property of thermal shock resistance. After the reforming TiO2-SiO2 ceramics doped by CeO2 was sintered at 1380℃, the bending strength reached to 83 MPa, and the thermal expansion coefficient was 9.8×10-6/℃within the temperature range of 25 ~ 800℃, which provides a promising basis of making equipped honeycomb catalyst of deNOx.

Molecular Dynamics Simulation of Temperature-dependent Flexibility of Thermophilic Xylose Isomerase

The complex model of Thermus thermophilus xylose isomerase （TtXI） with D-xylose was constructed, and molecular dynamics （MD） simulations were carried out at 300 and 360 K for 10 ns by NAMD2.5. The radius of gyration （Rg）, subunit interactions, and residue flexibility were analyzed. The results show that residues 60-69, 142-148, 169-172, and 332-340 have high flexibility at 300 and 360 K. Residues with higher flexibility at 360 K than that at 300 K can mainly be divided into two groups： one locates in the helix-loophelix region consisting of residues 55-80 in catalytic domain; the other at subunit interfaces. The Rg of catalytic domain at 360 K shows 0.16 A higher than that at 300 K, but Rg of small C-terminal domain has no obvious difference. The results indicate that enhanced Rg of catalytic domain may lead to the intense motion of the active site of TtXI and promote the D-xylose isomization reaction. Eight hydrogen bonds and five ion pairs are reduced at subunit interfaces at 360 K compared with 300 K, that may be the main reason for the decrease in rigidity and increase in activity at high temperature of TtXI. This result also help to explain the cold-adaption phenomenon of TtXI E372G mutant reported previously. Our results reveal the relationship between temperature and structure flexibility of TtXI, and play an important role in understanding the thermostability of thermophile protein with multiple subunits.

Mutation-Screening of Pleurotus Ferulae with High Temperature Tolerance by Nitrogen Ion Implantation

In order to obtain Pleurotus ferulae with high temperature tolerance, conidiophores of wild type strain ACK were implanted with nitrogen ions in energy of 5 -15 keV and dose of 1.5×10^15 - 1.5 × 10^16 cm^-2, and a mutant CGMCC1763 was isolated subsequently through thermotolerant screening method. It was found that during riper period the surface layer mycelium of the mutant in mushroom bag wasn＇t aging neither grew tegument even above 30℃. The mycelium endurable temperature of the mutant was increased by 5℃ compared to that of the wild type strain. The fruiting bodies growth temperature of the mutant was 18 -22℃ in daytime and 8 -14℃ at night. The highest growth temperature of fruiting bodies of the mutant was increased about 7℃ w.r.t, that of original strain. Through three generations investigations, it was found that the mutant CGMCC1763 was stable with high temperature tolerance.

Properties and catalytic mechanism of γ-glutamyltranspeptidase from B.subtilis NX-2

Sinceγ-glutamyltranspeptidase(GGT)especially catalyses the transfer of theγ-glutamyl moiety to a variety of amino acids and short peptides,GGT has important practical value for enzymatic synthesis ofγ-glutamyl compounds.In this paper,the GGT produced from Bacillus subtilis NX-2 was purified by a combination of ammonium sulfate fractionation and ion exchange chromatography,and the properties of purified GGT were investigated.At the conditions of pH 10.0,D-glutamine(D-Gln)/L-tryptophan(L-Trp)with a molar ratio of 5:7,a temperature 40℃ and a reaction time of 4 h,a higher conversion rate of 42%was obtained.According to the time course,the catalytic mechanism of enzymatic synthesis ofγ-D-glutamyl-L-tryptophan(γ-D-Gln-L-Trp)was discussed.It was demonstrated that the GGT can catalyze not only the reaction of transpeptidation,but also the irreversible hydrolysis of the products which results in the decrease of the yield of the products.The affinity parameter of GGT to D-Gln(Km)was 5.08 mmol·L-1 and the maximum reaction rate of transpeptidation(rmax)was determined as 0.034 mmol·min-1·L-1,while the affinity parameter of GGT toγ-D-Gln-L-Trp(K’m)was 2.267 mmol·L-1,and the maximum reaction rate of hydrolysis(r’max)was 0.012 mmol·min-1·L-1.

Architecture of severe fever with thrombocytopenia syndromevirus

Dear Editor,Severe fever with thrombocytopenia syndrome(SFTS)is an acute infectious disease caused by severe fever with thrombocytopenia syndrome virus(SFTSV)and is characterized by rapid onset,high mortality and widespread distribution.The fatality rate can be as high as 10%-30%,which is significantly higher than that of the hemorrhagic fever caused by Hantavirus in the same area(Song et al.,2018).However,no effective treatments or vaccines are available yet,and the underlying pathogenic mechanisms of the virus are poorly understood.

Recombinant aspartate aminotransferase-catalyzed synthesis of L-4-fluorophenylalanine

L-4-Fluorophenylalanine(FPhe)was prepared from 4-fluorophenylpyruvate(FPPA)catalyzed by aspartate aminotransferase(Asp-AT)of the recombinant E.coli BL21-pET/aspC.After 12 h enzymatic reaction,the FPPA conversion was over 90%and the yield of FPhe could be above 85%under the following optimal conditions:37uC,pH value range of 5.0–8.0,5.5 mass ratio of cell to FPPA,0.6%(w/v)of Tween 80,7.08 g/L FPPA,and 1.6 of molar ratio of L-Asp to FPPA.