1102 results about "Histidine" patented technology

Aspects of the disclosure relate to complexes and other aspects relate to formulations (e.g., aqueous, lyophilized forms) comprising such complexes (e.g., wherein each complex is of the exemplary formula shown below) comprising a phosphorodiamidate morpholino oligomer (e.g., useful for targeting DMD) covalently linked to an antibody (e.g., anti-TfR1 antibody). In some embodiments, the complexes are formulated with histidine (e.g., L-histidine) and sucrose at a specified pH (e.g., about 5.0 to 7.0). Also provided are uses of these formulations for treating a subject having a mutated DMD allele associated with Duchenne Muscular Dystrophy.

The invention provides recombinant escherichia coli with high yield of ergothioneine and a method for preparing ergothioneine, the recombinant escherichia coli co-expresses ergothioneine anabolic enzymes Egt1 and Egt2, the methyltransferase structural domain of the Egt1 is derived from trichoderma reesei, mycobacterium smegmatis EgtD or rhizopus nigricans, and the methyltransferase structural domain of the Egt2 is derived from the trichoderma reesei, the mycobacterium smegmatis EgtD or the rhizopus nigricans. The histidine sulfoxide synthase structural domain is derived from trichoderma reesei, schizosaccharomyces pombe or rhizopus nigricans, and the Egt2 is derived from claviceps purpurea, neurospora crassa or aspergillus niger. After the recombinant escherichia coli obtained by screening is cultured for 68 hours in a 5L fermentation tank, the yield of ergothioneine can reach 5g / L or above; wherein after recombinant escherichia coli co-expressing Egt1 enzyme (the structural domain of methyltransferase is derived from mycobacterium smegmatis EgtD, and the structural domain of histidine sulfoxide synthase is derived from trichoderma reesei) and Egt2 enzyme (derived from neurospora crassa) are cultured in a 5L fermentation tank for 68 hours, the yield of ergothioneine can reach 8.7 g / L, and the production intensity reaches 127.9 mg / (L.h).

The invention discloses a formate dehydrogenase mutant and application thereof in catalytic synthesis of D-mannitol, and belongs to the technical field of bioengineering. According to the formate dehydrogenase mutant provided by the invention, the 18th-site glutamic acid of wild-type formate dehydrogenase with an amino acid sequence shown as SEQ ID NO.2 is mutated into proline, the 57th-site asparagine is mutated into glutamic acid, the 70th-site histidine is mutated into tryptophan, the 235th-site serine is mutated into threonine, and the 316th-site valine is mutated into threonine, so that the formate dehydrogenase mutant is high in enzyme activity and catalytic activity; the coenzyme circulation efficiency during the production of D-mannitol can be obviously improved, so that the yield of D-mannitol can be effectively improved. When the genetically engineered bacterium co-expressed by the formate dehydrogenase mutant and the mannitol dehydrogenase mutant is used for catalyzing 150 g / L fructose to produce D-mannitol, the yield of D-mannitol within 15 h can reach 140 g / L or above.

The invention provides a composite reagent system and a chalcopyrite and sphalerite collecting method, and belongs to the technical field of mineral processing. The composite reagent system comprises a histidine derived functional group collecting agent and a black agent, and the histidine derived functional group collecting agent (containing a total sulfur ester group, a sulfydryl functional group and a side chain imidazole ring) serves as a core and is compounded with the black agent according to a specific proportion to form a target combination-synergistic interaction flotation mechanism. The histidine derivative collecting agent derives high-activity functional groups under the alkaline condition, and after sulfydryl is dissociated, stable chemical bonds are formed by the dissociated sulfydryl and metal ions on the surfaces of the chalcopyrite and the zinc sulfide. The black powder serves as an auxiliary collecting agent, and the collecting capacity of fine-grain or low-activity sulfide minerals is enhanced through chemical adsorption of dithiophosphate radicals and metal ions on the surfaces of the chalcopyrite and the sphalerite. After the two components are compounded, the selective enrichment efficiency of copper-zinc minerals in the flotation process is remarkably improved.

The invention discloses a graphene nanometer heavy anti-corrosion coating and a preparation method thereof, and belongs to the technical field of anti-corrosion coatings. The coating is prepared from the following components in parts by mass: 50 to 70 parts of diallyl bisphenol A type epoxy resin, 8 to 15 parts of histidine modifier, 12 to 20 parts of graphene nano composite modified filler, 5 to 10 parts of curing agent, 0.5 to 2 parts of flatting agent and 0.3 to 1 part of defoaming agent. The preparation method of the histidine modifier comprises the following steps: carrying out a Schiff base reaction on 1-palmitoyl-2-oleoyl ethanolamine and N-formyl-L-histidine to generate an intermediate A; reacting with a spiro quaternization reagent to form a quaternary ammonium salt intermediate B; and then compounding with aminopropyltriethoxysilane and silicotungstic heteropoly acid salt to obtain the product. The graphene nano-composite modified filler is prepared by modifying the surface of a graphene oxide / bentonite mutual intercalation layer structure through allyl trimethoxy silane. The graphene nano heavy anti-corrosion coating prepared by the invention forms a high-density cross-linked network, and has excellent barrier property, strong adhesive force, impact resistance and long-acting anti-corrosion performance.

The invention relates to the field of polypeptide compositions, in particular to a polypeptide metal chelate and application thereof in the field of cosmetics, and the polypeptide metal chelate is formed by chelating a polypeptide compound and a metal ion compound. The structure of the polypeptide compound is [gamma-Glu] n-AA, n is greater than or equal to 1, and AA is selected from glycine, alanine, valine, leucine, isoleucine, methionine (methionine), proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, asparaginic acid, glutamic acid, lysine, arginine or histidine; the polypeptide chelated zinc prepared by the invention has remarkable oil control and anti-inflammatory effects, and can be compounded with other raw materials to form cosmetics with oil control and acne removal effects.

The invention discloses a preparation method and application of a manganese-based amino acid coordination polymer, and belongs to the technical field of nano-enzymes and nano-drugs. Divalent manganese salt, histidine and other amino acids are subjected to a co-precipitation reaction to prepare the manganese-based amino acid coordination polymer, and the polymer is of a nanoparticle structure, small in size and high in stability, has enzyme-like activity, catalyzes hydrogen peroxide to generate high-toxicity hydroxyl free radicals and is used for specifically killing tumor cells. The catalyst has the capability of catalytically generating singlet oxygen in the presence of hydrogen peroxide. Meanwhile, the manganese-based amino acid complex has glutathione oxidase-like activity, consumes glutathione to overcome the resistance of tumors to oxidative stress, improves the chemical kinetic curative effect, and has anti-tumor application potential.

The invention discloses preparation of a bionic copper-based MOF nano-enzyme and application of the bionic copper-based MOF nano-enzyme in hydroquinone detection, and the bionic copper-based MOF nano-enzyme is prepared by the following method: dissolving terephthalic acid H2BDC and L-histidine His in N, N-dimethylformamide DMF to obtain a solution A; adding copper chloride CuCl2. 2H2O into the solution A obtained by C1, and stirring to form a uniform mixed solution; carrying out hydrothermal reaction on the mixed solution obtained from C2 for a certain time, centrifuging to obtain a solid precipitate, cleaning the solid precipitate, and drying to obtain the bionic Cu / His-MOF nano-enzyme; the invention also discloses an application of the sensor in hydroquinone detection. The bionic copper-based MOF nano-enzyme has the advantages of being simple and convenient to synthesize, high in substrate affinity, high in catalytic capacity and the like, and meanwhile, a rapid, sensitive and reliable HQ detection method is provided.

The invention relates to laccase as well as a mutant and application thereof, and belongs to the technical field of biology. The amino acid sequence of the laccase PnLac1 is as shown in SEQ ID NO. 2, and the nucleotide sequence of the laccase PnLac1 is as shown in SEQ ID NO. 1. The mutant is characterized in that aspartic acid at the 166th position of laccase PnLac1 is subjected to site-specific mutagenesis, histidine at the 348th position of laccase PnLac1 is subjected to site-specific mutagenesis, methionine at the 403th position of laccase PnLac1 is subjected to site-specific mutagenesis, or leucine at the 467th position of laccase PnLac1 is subjected to site-specific mutagenesis, amino acid sequences are shown as SEQ ID NO.4, SEQ ID NO.6, SEQ ID NO.8 and SEQ ID NO.10, and nucleotide sequences are shown as SEQ ID NO.3, SEQ ID NO.5, SEQ ID NO.7 and SEQ ID NO.9. The decoloring efficiency of the laccase PnLac1 on crystal violet reaches 5h, and the degradation rate reaches 75%. When the ABTS is used as a substrate, the enzyme activities of the laccase mutants H348F and L467M are respectively improved by 1.89 times and 1.65 times, and the ABTS has the potential of degrading stubborn substances; when guaiacol is used as a substrate, the enzyme activities of the laccase mutants D166A and M403F are respectively improved by 2.07 times and 3.72 times, and the guaiacol has a relatively high application prospect in the field of lignin.

The invention discloses an L-histidine transporter mutant and a method for increasing the yield of L-histidine, and the mutant has any one mutation of I20A, V28L, I20A-V28L and I20A-V21L-T28S relative to an escherichia coli wild type yeaS. The yield of the L-histidine of the recombinant escherichia coli containing the yeaS mutant protein is remarkably increased, it is indicated that the yeaS mutant protein and the coding gene of the yeaS mutant protein can be used for increasing the yield of the L-histidine, and the mutant can lay a good foundation for industrial efficient production of the L-histidine and downstream metabolites.

The invention relates to the technical field of microorganisms, and particularly discloses a recombinant microorganism and application thereof in fermentation production of decarboxylated carnosine. Compared with an original strain, the recombinant microorganism disclosed by the invention has the advantages that the expression of the mdtK gene is enhanced; the starting strain is escherichia coli capable of producing decarboxylated carnosine. When the recombinant microorganism is used for fermentation production, the yield of the decarboxylated carnosine can be increased, L-histidine, histamine or beta-alanine and other precursors do not need to be added in the production process, and an effective novel method is provided for industrial production of the decarboxylated carnosine.

The invention provides a preparation method of antitoxin serum containing an horse F (ab ') 2 fragment, and the specific steps are as follows: a recombinant streptococcus immunoglobulin G degrading enzyme is immobilized to obtain an immobilized enzyme chromatography column, the recombinant streptococcus immunoglobulin G degrading enzyme comprises a glutathione-S-transferase tag and a histidine tag; performing primary treatment on the immune plasma to obtain a pretreated antibody solution; the pretreatment antibody solution is added into an immobilized enzyme chromatography column for digestion, after digestion is completed, ultrafiltration, purification and solution preparation are sequentially conducted through an immobilized glutathione affinity column or a nickel affinity column, an antitoxin serum stock solution is obtained, and the antitoxin serum stock solution contains F (ab ') 2 fragments and does not contain Fc fragments, impure protein and small molecule impurities. Through the process steps, the Fc fragment and impure protein are effectively removed, and only the horse F (ab ') 2 fragment is reserved, so that the immunogenicity of antitoxin serum and the risk of causing anaphylactic reaction are remarkably reduced.

The invention relates to the technical field of biology, and discloses a carbonyl reductase mutant and application thereof in enzymatic synthesis of chiral alcohol. The amino acid sequence as shown in SEQ ID NO.2 is subjected to mutation that 36th lysine is mutated into any one of aspartic acid, threonine and valine, or / and 125th histidine is mutated into any one of lysine, serine and leucine, or 170th histidine is mutated into any one of lysine, cysteine and leucine. The carbonyl reductase mutants, especially single-site mutants Mut-T75K, Mut-T75D and Mut-E216M and a combined mutant Mut-T75K-E216M, with activity improved to different extents compared with that of a wild type are obtained, have excellent relative enzyme activity, thermal stability and substrate tolerance, have relatively high activity and stability for various chiral alcohols, and can be used for preparing the carbonyl reductase mutants. The catalyst has the advantages of high catalytic activity, high thermal stability, strong substrate tolerance, easiness in fermentation and the like.

The invention discloses a p-nitrophenyl ethyl esterase mutant with high enantioselectivity as well as a construction method and application of the p-nitrophenyl ethyl esterase mutant. The p-nitrophenyl ethyl esterase mutant is obtained by mutating an amino acid sequence of wild p-nitrophenyl ethyl esterase pnbA as shown in SEQ ID NO.1 according to one or a combination of more of the following modes: leucine at the 273rd site is mutated into aspartic acid, phenylalanine at the 314th site is mutated into histidine, and leucine at the 362nd site is mutated into arginine. The mutant pnbA-L273D / F314H / L362R provided by the invention shows optimal catalytic performance (E = 47.16) for racemization-acetic acid pinyl hydrate, the enantiomeric excess value of the mutant is 95.13%, the conversion rate of 1S, 5R-acetic acid pinyl hydrate is 90.42%, the enantioselectivity of the mutant is obviously higher than that of a wild type, and the mutant has great application potential in biological catalytic synthesis of monocyclic monoterpenoid chiral alcohols.

The invention relates to a biosynthesis method of cosmetic tripeptide GHK (glycine-histidine-lysine), which is characterized in that a GHK oligopeptide is prepared by carrying out microbial fermentation synthesis and trypsin specific hydrolysis on artificially designed GHK multiple artificial sequences. And on the basis of the original sequence, the GHK yield is improved by adding a specific interval sequence. Compared with a traditional chemical synthesis method, the GHK oligopeptide biosynthesis method has the advantages that raw materials are cheap and simple, steps are easy to implement, and the GHK oligopeptide biosynthesis method is environmentally friendly and beneficial to improving the application level of GHK tripeptide in the field of beauty makeup.

The invention provides an oxygen-carrying protein molecule and a preparation method and application thereof, and relates to the technical field of functional protein preparation, the oxygen-carrying protein molecule comprises at least one cysteine part and at least one histidine part, the cysteine part comprises acetyl or ethyl maleoyl, and the histidine part comprises histidine. The histidine moiety includes a benzimidazole derivative group. The benzimidazole derivative is adopted as an auxiliary molecule and participates in the modification process of the sulfydryl modified compound on the hemoglobin, the modification site selectivity is improved, the conformational change is reduced, and the modification degree is accurately controlled, so that the oxygen binding force P50 of the modified hemoglobin is effectively improved.

The invention discloses a diluent for whole blood lateral immunochromatography detection as well as a preparation method and a detection method thereof, and belongs to the technical field of immunochromatography detection. The diluent solves the technical problems of unsmooth chromatography, background interference, poor stability of detection results and the like caused by red blood cells during direct detection of whole blood samples. The diluent comprises a buffer system, an osmotic pressure regulator glycine, a nonionic surfactant polysorbate, an erythrocyte aggregation inducer polyvinylpyrrolidone, a dynamic viscosity regulator trehalose, a blocking protein, a stabilizer combination L-methionine and L-histidine, and a composite formula of water. Red blood cells are effectively induced to gather and intercept on the sample pad through the synergistic effect of all the components, and meanwhile the stability of the chromatography process and the activity of the detection reagent are maintained. The diluent is mainly used for lateral immunochromatography quantitative detection of markers such as pro-enkephalin, C-reactive protein, cardiac troponin I or N-terminal pro-brain natriuretic peptide in a whole blood sample.

The invention belongs to the technical field of immunodetection, and discloses a kit for detecting the ratio of proBDNF to maure BDNF based on structural dynamics guidance and a preparation method of the kit, the kit comprises a solid phase carrier and a detection reagent, the three antibodies are determined on the basis of full-length conformational kinetics analysis of brain-derived neurotrophic factors; the first capture antibody targets an innate disorder region (SEQ ID NO: 1) of a proBDNF propeptide region; the second capture antibody targets an innate disorder region (SEQ ID NO: 2) of a proBDNF propeptide region; the second capture antibody is a neo-epitope specific antibody, is specifically combined with an N terminal (SEQ ID NO: 2) exposed by maure BDNF enzyme digestion, and is combined with a free alpha-amino group strictly dependent on the first histidine; and the universal detection antibody is combined to a Loop 4 region (SEQ ID NO: 3) of the Mature structural domain. The problems of steric hindrance and cross reaction in traditional immunodetection are solved through a structural biology strategy, and accurate distinguishing and ratio quantification of proBDNF and maure BDNF are achieved.

The invention discloses a preparation method of an edible pectin film capable of monitoring and prolonging fruit freshness, which comprises the following steps: carrying out oxidation reaction on pectin and sodium periodate, then terminating the reaction and purifying to obtain oxidized pectin; the preparation method comprises the following steps: dissolving oxidized pectin in water, then adding histidine, and carrying out heating reaction at 60-120 DEG C for 1-3 hours to obtain a reaction product with pH-responsive fluorescence characteristics; adding a calcium chloride aqueous solution as a cross-linking agent into the reaction product, simultaneously adding glycerol as a plasticizer, stirring and mixing for 5-15 minutes at the temperature of 50-70 DEG C, and then stirring and mixing for 1.5-2.5 hours at the temperature of 20-30 DEG C to obtain a uniform film forming solution; pouring the film-forming liquid into a film, and drying to obtain an edible pectin film; the invention also provides the edible pectin film prepared by the preparation method. The prepared edible pectin film is mainly used for packaging fruits, and the freshness of the fruits can be visually displayed through fluorescence change while the fruits are kept fresh.

The invention relates to the field of agricultural protection preparations, in particular to preparation of gold nanoclusters and application of the gold nanoclusters to prevention and treatment of plant parasitic nematodes. The invention provides a preparation method of a gold nanocluster, which comprises the following steps: preparing by using HAuCl4 and L-His to obtain an L-type histidine modified gold nanocluster; the preparation method comprises the steps that a HAuCl4 aqueous solution and an L-His aqueous solution are evenly mixed and then incubated, an obtained reaction solution containing L-His-AuNCs is centrifuged and then subjected to aftertreatment such as ultrafiltration, and the gold nanocluster is obtained. The gold nanocluster can be used for preventing and treating pine wood nematodes.

The present invention relates to a highly concentrated, stable pharmaceutical formulation of a pharmaceutically active anti-HER2 antibody, such as e.g. Trastuzumab (HERCEPTIN™), Pertuzumab or T-DM1, or a mixture of such antibody molecules for subcutaneous injection. In particular, the present invention relates to formulations comprising, in addition to a suitable amount of the anti-HER2 antibody, an effective amount of at least one hyaluronidase enzyme as a combined formulation or for use in form of a co-formulation. The formulations comprise additionally at least one buffering agent, such as e.g. a histidine buffer, a stabilizer or a mixture of two or more stabilizers (e.g. a saccharide, such as e.g. α,α-trehalose dihydrate or sucrose, and optionally methionine as a second stabilizer), a nonionic surfactant and an effective amount of at least one hyaluronidase enzyme. Methods for preparing such formulations and their uses thereof are also provided.

The invention discloses a preparation method and application of collagen microspheres, and belongs to the technical field of genetic engineering. Two histidines are respectively inserted into the N end and the C end of the collagen B-domain amino acid sequence, the high polymerization self-assembly of the collagen is promoted by utilizing the metal chelating effect to form a three-dimensional network structure, and a histidine is further inserted into the middle of the collagen, so that the three-dimensional morphology transformation of the collagen assembly is realized, and a loose and porous microsphere structure is formed. Experiments prove that by controlling the number and position of His residues in the collagen B-domain amino acid sequence expressed by microbial cells, the three-dimensional morphology of collagen can be controlled, and the collagen microspheres are formed; the prepared collagen microspheres can significantly promote cell adhesion, extension and migration.

The invention belongs to the technical field of nano-enzymes, and particularly relates to a CuPH (at) KMO composite nano-enzyme material as well as a preparation method and application thereof. Aiming at the problems of poor catalytic activity, complex steps, high raw material cost and low biocompatibility of nano-enzyme prepared by the existing method, the preparation method comprises the following steps: by taking terephthalic acid and histidine as dual-coordination copper-based nano-enzyme as a precursor, introducing manganese oxide in situ under a hydrothermal condition; and the flower-like nano mimic enzyme which is uniform in size and has high laccase-like catalytic characteristics at the same time is synthesized. The composite nano-enzyme provided by the invention can catalytically oxidize phenol amine organic compounds under the condition that the pH value is 3-9, can realize the detection of the content of ergothioneine in cosmetics and nutritional supplement capsules, and can be applied to the field of cosmetic and food safety monitoring.

The invention discloses a method for efficiently producing ergothioneine by metabolic engineering modified escherichia coli and application, and belongs to the technical field of biology. By adopting the recombinant escherichia coli EGT-1-B * provided by the invention, glucose can be converted into ergothioneine; therefore, the raw materials are cheap and easy to obtain, additives and heavy metals which are harmful to human health are avoided, a good foundation is laid for later product purification, and the requirements of commercial application can be met. Furthermore, genes related to metabolism of histidine, methionine, cysteine and S-adenosylmethionine are further overexpressed in the recombinant escherichia coli EGT-1-B *, so that the content of precursor amino acid synthesized by the ergothioneine is increased, and meanwhile, after the gene yqaB is knocked out, the yield of the ergothioneine is further increased; the utilization rate of glucose to ergothioneine can be further improved, and the yield of ergothioneine can reach 140.29 mg / L.

The invention discloses a gelator and a preparation method and application thereof, the structural formula of the gelator is # imgabs0 #, R1 is a side chain group connected to an amino acid central carbon atom except an amino group, a carboxyl group and a hydrogen atom; the amino acid is selected from one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrole lysine; the amino acid is selected from one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrole lysine; r2 is alkyl with the carbon atom number of 16 to 19; and R3 is 9-fluorenyl methoxy carbonyl group or t-butyloxycarbonyl group. The gelator has a hydrophobic long alkyl tail chain, can spontaneously gather and assemble into a three-dimensional network structure through hydrogen bonds, pi-pi interaction and hydrophobic force, and fixes an oil phase in an oil solvent or an oil-water mixture in an effective manner to form high-strength gel.

The present invention relates to a highly concentrated, stable pharmaceutical formulation of a pharmaceutically active anti-HER2 antibody, such as e.g. Trastuzumab (HERCEPTIN™), Pertuzumab or T-DM1, or a mixture of such antibody molecules for subcutaneous injection. In particular, the present invention relates to formulations comprising, in addition to a suitable amount of the anti-HER2 antibody, an effective amount of at least one hyaluronidase enzyme as a combined formulation or for use in form of a co-formulation. The formulations comprise additionally at least one buffering agent, such as e.g. a histidine buffer, a stabilizer or a mixture of two or more stabilizers (e.g. a saccharide, such as e.g. α,α-trehalose dihydrate or sucrose, and optionally methionine as a second stabilizer), a nonionic surfactant and an effective amount of at least one hyaluronidase enzyme. Methods for preparing such formulations and their uses thereof are also provided.

The invention belongs to the technical field of bioengineering, and particularly relates to alginate lyase Alaa1 as well as a modification method and application thereof. The amino acid sequence of the alginate lyase Alya1 is as shown in SEQ ID NO. 1, and the nucleotide sequence of the Alya1 gene for coding the alginate lyase Alya1 is as shown in SEQ ID NO. 2. The 406th glutamic acid of the alginate lyase Alya1 is mutated into histidine or lysine, and the high temperature resistance, the thermal stability, the pH stability and the half-life period of the alginate lyase Alya1 are remarkably improved.

According to the application of the controllable delivery of the multi-membraneless compartment interlamellar substances in the cell-free system, two independent and coexisting protein enrichment phases are rapidly formed in the optimized cell-free system by utilizing the protein expression of a protein expression vector and adding histidine tag (His Tag) protein, namely, after the multi-membraneless compartment is formed, the two independent and coexisting protein enrichment phases are separated from the cell-free system, and the cell-free system can be used for controlling the delivery of the multi-membraneless compartment interlamellar substances in the cell-free system. And controllable delivery of micromolecular substances and macromolecular substances in multiple membrane-free zone chambers is carried out. The multiple membrane-free compartments constructed by the invention can controllably enrich specific active components and biochemical reactions in a cell-free system into the compartments and separate the specific active components and biochemical reactions from other complex metabolic reactions, and due to the high dynamic nature of the compartments, controllable communication between biomolecules and the external environment and among multiple compartments can be realized; further, the accuracy and controllability of metabolic reaction are greatly improved, and a solid foundation is laid for application of a cell-free system in the aspects of complex metabolic pathway exploration, multi-enzyme catalysis, drug delivery and the like.

The invention discloses a preparation method of a metal doped type hydroxyapatite nanoflower. The method specifically comprises the following steps: dispersing a calcium source and soluble metal salt into water, adding acid phosphate, urea and L-histidine, uniformly mixing, carrying out a hydrothermal reaction, mechanically stirring, filtering, washing, and drying a hydrothermal system precipitate to obtain the corresponding metal-doped hydroxyapatite nanoflower. Compared with the prior art, the metal-doped hydroxyapatite nanoflower prepared by the preparation method disclosed by the invention is directly assembled by nanosheets, and a single metal type can be doped in a customized manner. According to the method, water is used as a unique solvent, the use of an organic solvent is avoided, the pH does not need to be adjusted in advance, the technological process is simple, operation is convenient, equipment investment is small, and the method is suitable for industrial production.

The invention belongs to the technical field of microbial engineering and genetic engineering, and discloses escherichia coli for producing histidine as well as a construction method and application thereof. The escherichia coli contains a growth dependent promoter PprpB of a methyl isocitrate lyase gene prpB and / or a stable phase dependent promoter PydgI of an ornithine reverse transport protein / lysine permease gene ydgI. Escherichia coli for producing histidine uses growth dependent promoter PprpB of methylisocitrate lyase gene prpB to regulate expression of glutamine phosphoribose pyrophosphate transamidase gene purF and uses ornithine reverse transport protein / lysine permease gene (ydgI) The stable-phase dependent promoter PydgI regulates the expression of the ATP phosphoribosyltransferase gene hisG, so that the energy supply of thalli in early-stage cell growth and the metabolic flux of L-histidine in later-stage thalli production can be realized, and the balanced distribution of the metabolic flux between the cell growth of a microbial cell factory and the production of L-histidine is effectively balanced.