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WO2019151435A1 - Dispersant de nanotubes de carbone, liquide de dispersion de nanotubes de carbone et procédé de dispersion de nanotubes de carbone - Google Patents

Dispersant de nanotubes de carbone, liquide de dispersion de nanotubes de carbone et procédé de dispersion de nanotubes de carbone Download PDF

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Publication number
WO2019151435A1
WO2019151435A1 PCT/JP2019/003477 JP2019003477W WO2019151435A1 WO 2019151435 A1 WO2019151435 A1 WO 2019151435A1 JP 2019003477 W JP2019003477 W JP 2019003477W WO 2019151435 A1 WO2019151435 A1 WO 2019151435A1
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amino acid
seq
sequence
fibroin
acid sequence
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PCT/JP2019/003477
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Japanese (ja)
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健大 佐藤
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Ｓｐｉｂｅｒ株式会社
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/174—Derivatisation; Solubilisation; Dispersion in solvents
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans

Definitions

  • the present invention relates to a carbon nanotube dispersant, a carbon nanotube dispersion, and a carbon nanotube dispersion method.
  • Carbon nanotubes have characteristics such as high electrical conductivity, thermal conductivity, mechanical strength, and optical nonlinearity such as a saturable absorption effect. Utilizing these characteristics of CNTs, fuel cells, electrodes, electromagnetic shielding materials, conductive resins, field emission display (FED) members, storage materials for various gases such as hydrogen, devices for high-speed optical communication, lasers Applications to a wide range of fields such as electronics for devices, energy, and medicine are expected.
  • CNT has a property that it is difficult to solubilize and disperse, and a technique for efficiently dispersing CNT is required.
  • a CNT dispersant for example, a low-molecular surfactant, cyclodextrin, or a water-soluble organic polymer is known.
  • cyclodextrin cyclodextrin
  • a water-soluble organic polymer is known.
  • dispersion of CNTs using proteins for example, Non-Patent Document 1 to Non-Patent Document 3).
  • An object of the present invention is to provide a carbon nanotube dispersant that is excellent in dispersion stability of carbon nanotubes (CNT) and can sufficiently suppress aggregation and precipitation of CNTs.
  • the present inventors have found that by dispersing CNT in a solution containing fibroin and a solvent, aggregation and precipitation over time can be suppressed and stable dispersion can be achieved.
  • the present invention is based on this novel finding.
  • a carbon nanotube dispersant comprising a solution containing fibroin and a solvent.
  • a carbon nanotube dispersion liquid comprising carbon nanotubes and the carbon nanotube dispersant according to any one of [1] to [5].
  • the carbon nanotube dispersion liquid according to [6] wherein the content of the carbon nanotube is 10 parts by mass or less with respect to 100 parts by mass of the fibroin.
  • a carbon nanotube dispersant that has excellent dispersion stability of carbon nanotubes (CNT) and can sufficiently suppress aggregation and precipitation of CNTs.
  • the carbon nanotube dispersant (CNT dispersant) of the present invention comprises a solution containing fibroin and a solvent. Since the CNT dispersant of the present invention is excellent in CNT dispersion stability and can sufficiently suppress CNT aggregation and precipitation, it is suitably used as a CNT dispersion medium, for example, for preparing a CNT dispersion.
  • CNT used as the object which uses the CNT dispersing agent of this invention
  • well-known single layer or multilayer CNT can be used.
  • limiting in particular also in the manufacturing method of CNT used as object For example, any of the CNT synthesized by the arc discharge method, the laser ablation method, or the CVD method can be used.
  • solvent Any solvent can be used without particular limitation as long as it can dissolve or disperse fibroin.
  • the solvent for example, any of a nonpolar solvent and a polar solvent may be used.
  • the solvent examples include aprotic polar solvents such as dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) and N, N-dimethylacetamide (DMAc), organic acids ( Protic polar solvents such as formic acid, acetic acid, propionic acid, butyric acid) and alcohols (methanol, ethanol, propanol, hexafluoro-2-propanol (HFIP), etc.) and nonpolar solvents such as hexane. These solvent may be used individually by 1 type, and may be used in combination of 2 or more type.
  • aprotic polar solvents such as dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) and N, N-dimethylacetamide (DMAc)
  • organic acids Protic polar solvents such as formic acid, acetic acid, propionic
  • the solvent is preferably a high boiling point solvent from the viewpoint of safety, and more preferably, for example, an aprotic polar solvent having a boiling point of 140 to 200 ° C.
  • the high boiling point solvent include aprotic polar solvents such as dimethyl sulfoxide and N, N-dimethylformamide.
  • the solvent is preferably a protic polar solvent such as hexafluoro-2-propanol (HFIP) from the viewpoint of good fibroin solubility.
  • HFIP hexafluoro-2-propanol
  • the solution may further contain an inorganic salt.
  • an inorganic salt By adding an inorganic salt, the dispersion function of the CNT dispersant can be controlled.
  • Inorganic salts include, for example, metal halides (metal chloride, metal bromide, metal iodide, etc.) such as alkali metal halides and alkaline earth metal halides, metal nitrates, metal perchlorates, and metal thiocyanates. Salt.
  • the inorganic salt include lithium salts such as lithium chloride, lithium bromide, lithium iodide, lithium nitrate, lithium perchlorate, and lithium thiocyanate, calcium chloride, calcium bromide, calcium iodide, calcium nitrate, Calcium salts such as calcium perchlorate and calcium thiocyanate, iron salts such as iron chloride, iron bromide, iron iodide, iron nitrate, iron perchlorate and iron thiocyanate, aluminum chloride, aluminum bromide, iodine
  • Aluminum salts such as aluminum chloride, aluminum nitrate, aluminum perchlorate and aluminum thiocyanate
  • potassium salts such as potassium chloride, potassium bromide, potassium iodide, potassium nitrate, potassium perchlorate and potassium thiocyanate, sodium chloride, Sodium bromide, sodium iodide, sodium nitrate Sodium salts such as sodium perchlorate and sodium thiocyanate, zinc
  • Inorganic salts include alkali metal halides (for example, LiCl, LiBr, etc.), alkaline earth metal halides (for example, CaCl 2 ), alkaline earth metal nitrates (for example, Ca (NO 3 ) 2 and the like) and an alkali metal thiocyanate (for example, NaSCN, etc.).
  • alkali metal halides for example, LiCl, LiBr, etc.
  • alkaline earth metal halides for example, CaCl 2
  • alkaline earth metal nitrates for example, Ca (NO 3 ) 2 and the like
  • an alkali metal thiocyanate for example, NaSCN, etc.
  • the content of the inorganic salt is preferably in the range of 0.1 to 20% by mass, and in the range of 0.1 to 10% by mass when the total amount of the solution is 100% by mass. More preferably.
  • the content of the inorganic salt is preferably in the range of 5 to 10% by mass when the total amount of the solution is 100% by mass from the viewpoint of controlling the dispersibility of CNTs more quickly (effectively).
  • the content of the inorganic salt is in the range of 0.1 to 5% by mass when the total amount of the solution is 100% by mass from the viewpoint of slowly reaggregating while maintaining the dispersion of CNTs for a while. Is preferred.
  • Fibroin is not particularly limited, and includes naturally occurring fibroin and modified fibroin.
  • naturally-occurring fibroin means fibroin having the same amino acid sequence as naturally-occurring fibroin
  • modified fibroin means fibroin having an amino acid sequence different from that of naturally-occurring fibroin. To do.
  • the fibroin according to the present embodiment is, for example, a domain sequence represented by Formula 1: [(A) n motif-REP] m or Formula 2: [(A) n motif-REP] m- (A) n motif. It may be a protein containing
  • an amino acid sequence (N-terminal sequence and C-terminal sequence) may be further added to either one or both of the N-terminal side and the C-terminal side of the domain sequence.
  • the N-terminal sequence and the C-terminal sequence are not limited to these, but are typically regions having no amino acid motif repeat characteristic of fibroin and consisting of about 100 amino acids.
  • domain sequence refers to a fibroin-specific crystal region (typically corresponding to the (A) n motif in the amino acid sequence) and an amorphous region (typically in the REP of the amino acid sequence).
  • (A) n motif represents an amino acid sequence mainly composed of alanine residues, and the number of amino acid residues is 2 to 27.
  • the number of amino acid residues of the n motif may be 2 to 20, 4 to 27, 4 to 20, 8 to 20, 10 to 20, 4 to 16, 8 to 16, or 10 to 16.
  • the ratio of the number of alanine residues to the total number of amino acid residues in the (A) n motif may be 40% or more, such as 60% or more, 70% or more, 80% or more, 83% or more, 85% or more, It may be 86% or more, 90% or more, 95% or more, or 100% (meaning that it is composed only of alanine residues).
  • a plurality of (A) n motifs present in the domain sequence may be composed of at least seven alanine residues alone.
  • REP indicates an amino acid sequence composed of 2 to 200 amino acid residues.
  • REP may be an amino acid sequence composed of 10 to 200 amino acid residues.
  • m represents an integer of 2 to 300, and may be an integer of 10 to 300.
  • a plurality of (A) n motifs may have the same amino acid sequence or different amino acid sequences.
  • Plural REPs may have the same amino acid sequence or different amino acid sequences.
  • Naturally occurring fibroin examples include a domain sequence represented by Formula 1: [(A) n motif-REP] m or Formula 2: [(A) n motif-REP] m- (A) n motif. Mention may be made of proteins containing. Specific examples of naturally occurring fibroin include fibroin produced by insects or spiders.
  • fibroin produced by insects include, for example, Bombyx mori, Kwako (Bombyx mandaraina), Tengea (Antheraea yamanai), ⁇ ⁇ (Antereaperanii), ⁇ ⁇ (Eriothyraminey) ), Silkworms produced by silkworms, such as Samia cythia, chestnut worms (Caligula japonica), Chuser moth (Antherea mylitta), Antheraea assama, and vespax (Vespaxia spp.) Hornet silk protein.
  • fibroin produced by insects include silkworm fibroin L chain (GenBank accession number M76430 (base sequence) and AAA27840.1 (amino acid sequence)).
  • Fibroin produced by spiders includes, for example, spiders belonging to the genus spider (Araneus spp.) Such as the spider spider, the spider spider, the red spider spider, and the bean spider, the genus spiders of the genus Araneus, the spider spider spider, the spider spider genus e Spiders, spiders such as spiders, spiders belonging to the genus Spider, spiders belonging to the genus Pronos, spiders belonging to the genus Trinofunda, such as Torinofundamas (genus Cyrtarachne) Spiders belonging to the genus (Gasteracantha), spiders belonging to the genus Spider (Ordgarius genus), such as the spiders, the spiders, and the spiders belonging to the genus Ordgarius Spiders belonging to the genus Argiope, such as the genus Argiope, spiders belonging to the genus Arachnura, such as the white-tailed spider, spiders belonging to the
  • Spiders belonging to the genus Azumigumi (Menosira), spiders belonging to the genus Dyschiriognatha (genus Dyschiriognatha) such as the common spider spider, the black spider spider, the genus Spider genus belonging to the genus Spider belonging to the genus (L) and the genus Spider belonging to the genus Usd Produced by spiders belonging to the family Tetragnathidae such as spiders belonging to the genus Prostenops
  • Examples include spider silk protein.
  • the spider silk protein include dragline proteins such as MaSp (MaSp1 and MaSp2) and ADF (ADF3 and ADF4), MiSp (MiSp1 and MiSp2), and the like.
  • spider silk proteins produced by spiders include, for example, fibroin-3 (adf-3) [derived from Araneus diadematus] (GenBank accession numbers AAC47010 (amino acid sequence), U47855 (base sequence)), fibroin-4 (adf-4) [derived from Araneus diadematus] (GenBank accession number AAC47011 (amino acid sequence), U47856 (base sequence)), dragline silk protein spiroin 1 [derived from Nephila clavipes] (GenBank accession number 4) ), U37520 (base sequence)), major ampulate spidro n 1 [derived from Latroductus hesperus] (GenBank accession number ABR68856 (amino acid sequence), EF595246 (base sequence)), dragline silk protein spidolin 2 [derived from Nephila clavata (GenBank accession number AAL32 base sequence 44 AAL32 base sequence amino acid 44, amino acid sequence 44 AAL47)
  • Naturally derived fibroin include fibroin whose sequence information is registered in NCBI GenBank.
  • sequence information is registered in NCBI GenBank.
  • spidin, sample, fibroin, “silk and polypeptide”, or “silk and protein” is described as a keyword in DEFINITION from sequences including INV as DIVISION among the sequence information registered in NCBI GenBank. It can be confirmed by extracting a character string of a specific product from the sequence, CDS, and a sequence in which the specific character string is described from SOURCE to TISSUE TYPE.
  • the modified fibroin is, for example, a modified amino acid sequence based on the amino acid sequence of naturally occurring fibroin (for example, a modified amino acid sequence by modifying the gene sequence of naturally cloned fibroin).
  • it may be one that is artificially designed and synthesized without relying on natural fibroin (for example, one having a desired amino acid sequence by chemically synthesizing a nucleic acid encoding the designed amino acid sequence).
  • the modified fibroin is, for example, a modification of the amino acid sequence corresponding to, for example, substitution, deletion, insertion and / or addition of one or more amino acid residues to the cloned natural fibroin gene sequence. Can be obtained at Substitution, deletion, insertion and / or addition of amino acid residues can be carried out by methods well known to those skilled in the art such as partial-directed mutagenesis. Specifically, Nucleic Acid Res. 10, 6487 (1982), Methods in Enzymology, 100, 448 (1983), and the like.
  • the modified fibroin may be, for example, a modified fibroin derived from a silk protein produced by a silkworm, or a modified fibroin derived from a spider silk protein produced by a spider.
  • modified fibroin examples include modified fibroin (first modified fibroin) derived from the large sphincter bookmark silk protein produced in the spider large bottle gland, modified fibroin with reduced glycine residue content (Second modified fibroin), (A) modified fibroin with reduced n- motif content (third modified fibroin), glycine residue content, and (A) n- motif content reduced
  • modified fibroin fourth modified fibroin
  • a modified fibroin having a domain sequence that locally includes a region having a large hydrophobicity index fifth modified fibroin
  • a domain sequence having a reduced glutamine residue content Modified fibroin may be mentioned.
  • the modified fibroin derived from the large sphincter bookmark silk protein produced in the spider large bottle-like gland includes a domain sequence represented by Formula 1: [(A) n motif-REP] m
  • the protein containing is mentioned.
  • n is preferably an integer of 3 to 20, more preferably an integer of 4 to 20, still more preferably an integer of 8 to 20, still more preferably an integer of 10 to 20.
  • An integer of ⁇ 16 is even more preferred, an integer of 8-16 is particularly preferred, and an integer of 10-16 is most preferred.
  • the number of amino acid residues constituting REP is preferably 10 to 200 residues, more preferably 10 to 150 residues, and 20 to 100 residues. More preferably, it is more preferably 20 to 75 residues.
  • the total number of glycine residues, serine residues and alanine residues contained in the amino acid sequence represented by the formula 1: [(A) n motif-REP] m is an amino acid residue. The total number is preferably 40% or more, more preferably 60% or more, and even more preferably 70% or more.
  • the first modified fibroin comprises an amino acid sequence unit represented by Formula 1: [(A) n motif-REP] m , and the C-terminal sequence is represented by any one of SEQ ID NOs: 1 to 3, Alternatively, it may be a polypeptide that is an amino acid sequence having 90% or more homology with the amino acid sequence shown in any one of SEQ ID NOs: 1 to 3.
  • the amino acid sequence shown in SEQ ID NO: 1 is identical to the amino acid sequence consisting of 50 amino acids at the C-terminal of the amino acid sequence of ADF3 (GI: 1263287, NCBI), and the amino acid sequence shown in SEQ ID NO: 2 is the sequence
  • the amino acid sequence shown in SEQ ID NO: 1 is identical to the amino acid sequence obtained by removing 20 residues from the C-terminal, and the amino acid sequence shown in SEQ ID NO: 3 has 29 residues removed from the C-terminal of the amino acid sequence shown in SEQ ID NO: 1. It is identical to the amino acid sequence.
  • the amino acid sequence represented by SEQ ID NO: 4 or (1-ii) the amino acid sequence represented by SEQ ID NO: 4 has a sequence identity of 90% or more. Mention may be made of modified fibroin comprising an amino acid sequence having. The sequence identity is preferably 95% or more.
  • the amino acid sequence represented by SEQ ID NO: 4 is an amino acid sequence of ADF3 in which an amino acid sequence (SEQ ID NO: 5) consisting of a start codon, a His10 tag and an HRV3C protease (Human rhinovirus 3C protease) recognition site is added to the N-terminus.
  • the 13th repeat region was increased to approximately double, and the translation was mutated to terminate at the 1154th amino acid residue.
  • the C-terminal amino acid sequence of the amino acid sequence shown in SEQ ID NO: 4 is identical to the amino acid sequence shown in SEQ ID NO: 3.
  • the modified fibroin (1-i) may be composed of the amino acid sequence represented by SEQ ID NO: 4.
  • the modified fibroin in which the content of glycine residues is reduced has an amino acid sequence in which the domain sequence of the modified fibroin has a reduced content of glycine residues compared to naturally occurring fibroin. It can be said that the second modified fibroin has an amino acid sequence corresponding to at least one or more glycine residues in REP substituted with another amino acid residue as compared with naturally occurring fibroin. .
  • the second modified fibroin has a domain sequence of GGX and GPGXX in REP (where G is a glycine residue, P is a proline residue, and X is an amino acid residue other than glycine) as compared to naturally occurring fibroin.
  • G is a glycine residue
  • P is a proline residue
  • X is an amino acid residue other than glycine
  • at least one glycine residue in at least one or more of the motif sequences is substituted with another amino acid residue. May be.
  • the ratio of the motif sequence in which the above glycine residue is replaced with another amino acid residue may be 10% or more with respect to the entire motif sequence.
  • the second modified fibroin comprises a domain sequence represented by Formula 1: [(A) n motif-REP] m , and is located on the most C-terminal side from the domain sequence (A) from the n motif to the domain sequence.
  • the number of alanine residues relative to the total number of amino acid residues in the n motif may be 83% or more, preferably 86% or more, more preferably 90% or more, and 95% or more. More preferably, it is 100% (meaning that it is composed only of alanine residues).
  • the second modified fibroin is preferably one in which the content ratio of the amino acid sequence consisting of XGX is increased by substituting one glycine residue of the GGX motif with another amino acid residue.
  • the content ratio of the amino acid sequence consisting of GGX in the domain sequence is preferably 30% or less, more preferably 20% or less, still more preferably 10% or less, % Or less is even more preferable, 4% or less is even more preferable, and 2% or less is particularly preferable.
  • the content ratio of the amino acid sequence consisting of GGX in the domain sequence can be calculated by the same method as the method for calculating the content ratio (z / w) of the amino acid sequence consisting of XGX below.
  • a fibroin modified fibroin or naturally-occurring fibroin containing a domain sequence represented by Formula 1: [(A) n motif-REP] m , (A) n located closest to the C-terminal side from the domain sequence
  • An amino acid sequence consisting of XGX is extracted from all REPs included in the sequence excluding the sequence from the motif to the C-terminal of the domain sequence.
  • z / w (%) can be calculated by dividing z by w.
  • z / w is preferably 50.9% or more, more preferably 56.1% or more, further preferably 58.7% or more, and 70% or more. It is still more preferable that it is 80% or more. Although there is no restriction
  • the second modified fibroin is obtained by, for example, modifying a cloned natural fibroin gene sequence so as to encode another amino acid residue by substituting at least a part of a base sequence encoding a glycine residue. Can be obtained. At this time, one glycine residue in GGX motif and GPGXX motif may be selected as a glycine residue to be modified, or substitution may be performed so that z / w is 50.9% or more.
  • an amino acid sequence satisfying the above-described aspect can be designed from the amino acid sequence of naturally derived fibroin, and a nucleic acid encoding the designed amino acid sequence can be obtained by chemical synthesis.
  • one or more amino acid residues are further substituted or deleted.
  • the amino acid sequence corresponding to the insertion and / or addition may be modified.
  • the other amino acid residue is not particularly limited as long as it is an amino acid residue other than glycine residue, but valine (V) residue, leucine (L) residue, isoleucine (I) residue, methionine ( M) hydrophobic amino acid residues such as proline (P) residue, phenylalanine (F) residue and tryptophan (W) residue, glutamine (Q) residue, asparagine (N) residue, serine (S ) Residues, lysine (K) residues and glutamic acid (E) residues are preferred, and valine (V) residues, leucine (L) residues, isoleucine (I) residues and glutamine ( Q) residue is more preferable, and glutamine (Q) residue is more preferable.
  • modified fibroin (2-i) the amino acid sequence represented by SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, or (2-ii) SEQ ID NO: 6, sequence Mention may be made of modified fibroin comprising an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in No. 7, SEQ ID No. 8 or SEQ ID No. 9.
  • the modified fibroin (2-i) will be described.
  • the amino acid sequence represented by SEQ ID NO: 6 is obtained by substituting all GGX in REP of the amino acid sequence represented by SEQ ID NO: 10 corresponding to naturally occurring fibroin with GQX.
  • the amino acid sequence represented by SEQ ID NO: 7 is the amino acid sequence represented by SEQ ID NO: 6, wherein every two (A) n motifs are deleted from the N-terminal side to the C-terminal side, and further before the C-terminal sequence.
  • One [(A) n motif-REP] is inserted into the.
  • the amino acid sequence represented by SEQ ID NO: 8 has two alanine residues inserted at the C-terminal side of each (A) n motif of the amino acid sequence represented by SEQ ID NO: 7, and a part of glutamine (Q) residues. Substituted with a serine (S) residue and a part of the amino acid at the N-terminal side was deleted so as to be almost the same as the molecular weight of SEQ ID NO: 7.
  • the amino acid sequence shown in SEQ ID NO: 9 is a region of 20 domain sequences present in the amino acid sequence shown in SEQ ID NO: 11 (however, several amino acid residues on the C-terminal side of the region are substituted). Is a sequence in which a His tag is added to the C-terminal of the sequence repeated four times.
  • the value of z / w in the amino acid sequence represented by SEQ ID NO: 10 (corresponding to naturally occurring fibroin) is 46.8%.
  • the z / w values of the amino acid sequence shown by SEQ ID NO: 6, the amino acid sequence shown by SEQ ID NO: 7, the amino acid sequence shown by SEQ ID NO: 8, and the amino acid sequence shown by SEQ ID NO: 9 are 58.7%, 70.1%, 66.1% and 70.0%.
  • the value of x / y at the ratio of the amino acid sequences shown in SEQ ID NO: 10, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 and SEQ ID NO: 9 (described later) 1: 1.8 to 11.3 is: 15.0%, 15.0%, 93.4%, 92.7% and 89.3%, respectively.
  • the modified fibroin (2-i) may be composed of the amino acid sequence represented by SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9.
  • the modified fibroin (2-ii) includes an amino acid sequence having 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9.
  • the modified fibroin of (2-ii) is also a protein containing a domain sequence represented by Formula 1: [(A) n motif-REP] m .
  • the sequence identity is preferably 95% or more.
  • the modified fibroin of (2-ii) has 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, and is contained in REP (XGX ( Where X is an amino acid residue other than glycine.) Z / w where z is the total number of amino acid residues of the amino acid sequence consisting of z and w is the total number of amino acid residues of REP in the domain sequence. Is preferably 50.9% or more.
  • the second modified fibroin may contain a tag sequence at one or both of the N-terminal and C-terminal. This makes it possible to isolate, immobilize, detect and visualize the modified fibroin.
  • tag sequences include affinity tags that use specific affinity (binding property, affinity) with other molecules.
  • affinity tag include a histidine tag (His tag).
  • His tag is a short peptide with about 4 to 10 histidine residues, and has the property of binding specifically to metal ions such as nickel. Therefore, the isolation of modified fibroin by metal chelating chromatography (chelating metal chromatography) Can be used.
  • Specific examples of the tag sequence include the amino acid sequence represented by SEQ ID NO: 12 (amino acid sequence including His tag sequence and hinge sequence).
  • GST glutathione-S-transferase
  • MBP maltose-binding protein
  • an “epitope tag” using an antigen-antibody reaction can also be used.
  • a peptide (epitope) exhibiting antigenicity as a tag sequence, an antibody against the epitope can be bound.
  • HA peptide sequence of hemagglutinin of influenza virus
  • myc tag peptide sequence of hemagglutinin of influenza virus
  • FLAG tag peptide sequence of hemagglutinin of influenza virus
  • a tag sequence that can be separated with a specific protease can also be used.
  • the modified fibroin from which the tag sequence has been separated can also be recovered.
  • modified fibroin containing the tag sequence (2-iii) the amino acid sequence represented by SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15, or (2-iv) Mention may be made of modified fibroin comprising an amino acid sequence having a sequence identity of 90% or more with the amino acid sequence shown in SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15.
  • amino acid sequences represented by SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14 and SEQ ID NO: 15 are SEQ ID NO: 10, SEQ ID NO: 18, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, respectively.
  • an amino acid sequence represented by SEQ ID NO: 12 (including a His tag sequence and a hinge sequence) is added to the N-terminus of the amino acid sequence represented by SEQ ID NO: 9.
  • the modified fibroin (2-iii) may be composed of the amino acid sequence represented by SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15.
  • the modified fibroin (2-iv) includes an amino acid sequence having 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15.
  • the modified fibroin of (2-iv) is also a protein containing a domain sequence represented by Formula 1: [(A) n motif-REP] m .
  • the sequence identity is preferably 95% or more.
  • the modified fibroin of (2-iv) has an XGX (which has 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15 and is contained in REP ( Where X is an amino acid residue other than glycine.) Z / w where z is the total number of amino acid residues of the amino acid sequence consisting of z and w is the total number of amino acid residues of REP in the domain sequence. Is preferably 50.9% or more.
  • the second modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host.
  • the sequence of the secretion signal can be appropriately set according to the type of host.
  • a modified fibroin with a reduced content of n motif is a domain sequence whose amino acid sequence has a reduced content of n motif compared to naturally occurring fibroin (A) Has an array. It can be said that the domain sequence of the third modified fibroin has an amino acid sequence corresponding to the deletion of at least one or more (A) n motifs, as compared to naturally occurring fibroin.
  • the third modified fibroin may have an amino acid sequence corresponding to 10% to 40% deletion of the (A) n motif from naturally occurring fibroin.
  • the third modification fibroin its domain sequence, compared to the naturally occurring fibroin, at least from the N-terminal side toward the C-terminal one to three (A) n motif every one (A) n motif May have an amino acid sequence corresponding to deletion of.
  • the third modified fibroin has a domain sequence that is at least two consecutive from the N-terminal side to the C-terminal side compared to the naturally occurring fibroin (A) deletion of the n motif, and one (A ) It may have an amino acid sequence corresponding to the deletion of the n motif repeated in this order.
  • the third modified fibroin may have an amino acid sequence whose domain sequence corresponds to that at least every two (A) n motifs are deleted from the N-terminal side to the C-terminal side. .
  • the third modified fibroin includes a domain sequence represented by Formula 1: [(A) n motif-REP] m , and two adjacent [(A) n motifs from the N-terminal side toward the C-terminal side. -REP]
  • the ratio of the number of amino acid residues in the other REP is 1.8 to
  • x the maximum total value of the total number of amino acid residues of two adjacent [(A) n motif-REP] units that becomes 11.3
  • x the total number of amino acid residues in the domain sequence is y
  • it may have an amino acid sequence in which x / y is 20% or more, 30% or more, 40% or more, or 50% or more.
  • the number of alanine residues relative to the total number of amino acid residues in the n motif may be 83% or more, preferably 86% or more, more preferably 90% or more, and 95% or more. More preferably, it is 100% (meaning that it is composed only of alanine residues).
  • FIG. 1 shows a domain sequence obtained by removing N-terminal sequence and C-terminal sequence from fibroin.
  • the domain sequence is from the N-terminal side (left side): (A) n motif-first REP (50 amino acid residues)-(A) n motif-second REP (100 amino acid residues)-(A) n Motif-third REP (10 amino acid residues)-(A) n motif-fourth REP (20 amino acid residues)-(A) n motif-fifth REP (30 amino acid residues)-(A) It has a sequence called n motif.
  • FIG. 1 includes pattern 1 (comparison between the first REP and the second REP, and comparison between the third REP and the fourth REP), pattern 2 (comparison between the first REP and the second REP, and 4th REP and 5th REP), pattern 3 (2nd REP and 3rd REP comparison, 4th REP and 5th REP comparison), pattern 4 (first REP and Comparison of the second REP).
  • pattern 1 compare between the first REP and the second REP, and comparison between the third REP and the fourth REP
  • pattern 2 comparison between the first REP and the second REP, and 4th REP and 5th REP
  • pattern 3 (2nd REP and 3rd REP comparison, 4th REP and 5th REP comparison
  • pattern 4 first REP and Comparison of the second REP
  • the number of amino acid residues of each REP in the two adjacent [(A) n motif-REP] units selected is compared.
  • each pattern the number of all amino acid residues of two adjacent [(A) n motif-REP] units indicated by solid lines is added (not only REP but also (A) the number of amino acid residues of the n motif. is there.). Then, the total value added is compared, and the total value (maximum value of the total value) of the pattern having the maximum total value is set as x. In the example shown in FIG. 1, the total value of pattern 1 is the maximum.
  • x / y (%) can be calculated by dividing x by the total number of amino acid residues y of the domain sequence.
  • x / y is preferably 50% or more, more preferably 60% or more, still more preferably 65% or more, and even more preferably 70% or more. Preferably, it is still more preferably 75% or more, and particularly preferably 80% or more. There is no restriction
  • x / y is preferably 89.6% or more, and when the jagged ratio is 1: 1.8 to 3.4, x / y / Y is preferably 77.1% or more, and when the jagged ratio is 1: 1.9 to 8.4, x / y is preferably 75.9% or more, and the jagged ratio is 1 In the case of 1.9 to 4.1, x / y is preferably 64.2% or more.
  • a plurality of third modified fibroins are present in the domain sequence (A)
  • x / y is 46.4% or more It is preferably 50% or more, more preferably 55% or more, still more preferably 60% or more, still more preferably 70% or more, and more preferably 80% or more. It is particularly preferred.
  • one or a plurality of sequences encoding the n motif is deleted so that x / y is 64.2% or more from the cloned gene sequence of naturally occurring fibroin.
  • an amino acid sequence corresponding to the deletion of one or more (A) n motifs is designed so that x / y is 64.2% or more from the amino acid sequence of naturally occurring fibroin. It can also be obtained by chemically synthesizing a nucleic acid encoding the amino acid sequence.
  • one or more amino acid residues are further substituted, deleted, inserted and / or added.
  • the amino acid sequence corresponding to this may be modified.
  • modified fibroin As more specific examples of the third modified fibroin, (3-i) SEQ ID NO: 18, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, or (3-ii) SEQ ID NO: 18, sequence Mention may be made of modified fibroin comprising an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in No. 7, SEQ ID No. 8 or SEQ ID No. 9.
  • the modified fibroin (3-i) will be described.
  • the amino acid sequence represented by SEQ ID NO: 18 is the amino acid sequence represented by SEQ ID NO: 10 corresponding to naturally occurring fibroin, wherein (A) n motif is deleted every two from the N-terminal side to the C-terminal side. Furthermore, one [(A) n motif-REP] is inserted in front of the C-terminal sequence.
  • the amino acid sequence shown in SEQ ID NO: 7 is obtained by substituting all GGX in REP of the amino acid sequence shown in SEQ ID NO: 18 with GQX.
  • the amino acid sequence represented by SEQ ID NO: 8 has two alanine residues inserted at the C-terminal side of each (A) n motif of the amino acid sequence represented by SEQ ID NO: 7, and a part of glutamine (Q) residues. Substituted with a serine (S) residue and a part of the amino acid at the N-terminal side was deleted so as to be almost the same as the molecular weight of SEQ ID NO: 7.
  • the amino acid sequence shown in SEQ ID NO: 9 is a region of 20 domain sequences present in the amino acid sequence shown in SEQ ID NO: 11 (however, several amino acid residues on the C-terminal side of the region are substituted). Is a sequence in which a His tag is added to the C-terminal of the sequence repeated four times.
  • the value of x / y in the amino acid sequence represented by SEQ ID NO: 10 (corresponding to naturally-occurring fibroin) at a jagged ratio of 1: 1.8 to 11.3 is 15.0%.
  • the value of x / y in the amino acid sequence shown by SEQ ID NO: 18 and the amino acid sequence shown by SEQ ID NO: 7 are both 93.4%.
  • the value of x / y in the amino acid sequence represented by SEQ ID NO: 8 is 92.7%.
  • the value of x / y in the amino acid sequence represented by SEQ ID NO: 9 is 89.3%.
  • the z / w values in the amino acid sequences represented by SEQ ID NO: 10, SEQ ID NO: 18, SEQ ID NO: 7, SEQ ID NO: 8 and SEQ ID NO: 9 are 46.8%, 56.2%, 70.1% and 66. respectively. 1% and 70.0%.
  • the modified fibroin (3-i) may consist of the amino acid sequence represented by SEQ ID NO: 18, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9.
  • the modified fibroin (3-ii) includes an amino acid sequence having 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 18, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9.
  • the modified fibroin of (3-ii) is also a protein containing a domain sequence represented by Formula 1: [(A) n motif-REP] m .
  • the sequence identity is preferably 95% or more.
  • the modified fibroin of (3-ii) has 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 18, SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, and from the N-terminal side to the C-terminal side
  • the number of amino acid residues of REP of two adjacent [(A) n motif-REP] units is sequentially compared, and the number of amino acid residues of REP having a small number of amino acid residues is 1, the other
  • x / y is 64.2% or more, where x is the maximum total value of the total number of bases and y is the total number of amino acid residues in the domain sequence.
  • the third modified fibroin may contain the tag sequence described above at one or both of the N-terminal and C-terminal.
  • modified fibroin containing the tag sequence (3-iii) SEQ ID NO: 17, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15, or (2-iv) sequence
  • modified fibroin comprising an amino acid sequence having a sequence identity of 90% or more with the amino acid sequence shown in SEQ ID NO: 17, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15.
  • amino acid sequences represented by SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 13, SEQ ID NO: 11, SEQ ID NO: 14 and SEQ ID NO: 15 are SEQ ID NO: 10, SEQ ID NO: 18, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, respectively.
  • an amino acid sequence represented by SEQ ID NO: 12 (including a His tag sequence and a hinge sequence) is added to the N-terminus of the amino acid sequence represented by SEQ ID NO: 9.
  • the modified fibroin may be composed of the amino acid sequence represented by SEQ ID NO: 17, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15.
  • the modified fibroin (3-iv) includes an amino acid sequence having 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 17, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15.
  • the modified fibroin of (3-iv) is also a protein containing a domain sequence represented by Formula 1: [(A) n motif-REP] m .
  • the sequence identity is preferably 95% or more.
  • the modified fibroin (3-iv) has 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 17, SEQ ID NO: 11, SEQ ID NO: 14 or SEQ ID NO: 15, and from the N-terminal side to the C-terminal side.
  • the other X is the maximum total value of the total number of amino acid residues of two adjacent [(A) n motif-REP] units with a ratio of the number of amino acid residues of REP of 1.8 to 11.3.
  • x / y is preferably 64.2% or more.
  • the third modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host.
  • the sequence of the secretion signal can be appropriately set according to the type of host.
  • the content of glycine residues, and (A) n motifs modified fibroin content is reduced in the (fourth modified fibroin), the domain sequence is compared to the naturally occurring fibroin, (A) n motif In addition to having a reduced content of glycine residues, it has an amino acid sequence with a reduced content of glycine residues.
  • the domain sequence of the fourth modified fibroin has at least one or more (A) n motifs deleted as compared to naturally occurring fibroin, and at least one or more glycine residues in the REP. It can be said to have an amino acid sequence corresponding to the substitution with another amino acid residue.
  • the fourth modified fibroin includes the modified fibroin (second modified fibroin) in which the content of the glycine residue described above is reduced, and (A) the modified fibroin (third in which the content of the n motif is reduced). It is a modified fibroin having the characteristics of modified fibroin). Specific embodiments and the like are as described in the second modified fibroin and the third modified fibroin.
  • modified fibroin (4-i) the amino acid sequence represented by SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9, (4-ii) SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: Mention may be made of modified fibroin comprising an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in FIG.
  • modified fibroin comprising the amino acid sequence represented by SEQ ID NO: 7, SEQ ID NO: 8 or SEQ ID NO: 9 are as described above.
  • a modified fibroin having a domain sequence including a region having a large hydrophobic index locally has a domain sequence of one or more amino acid residues in REP as compared to naturally occurring fibroin. Is replaced with an amino acid residue having a large hydrophobicity index and / or one or more amino acid residues having a large hydrophobicity index are inserted into REP. It may have an amino acid sequence including a region.
  • the region where the hydrophobic index is locally large is preferably composed of 2 to 4 amino acid residues.
  • the amino acid residue having a large hydrophobicity index is an amino acid selected from isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), methionine (M) and alanine (A). More preferably, it is a residue.
  • the fifth modified fibroin has one or more amino acid residues in REP substituted with amino acid residues having a higher hydrophobicity index and / or one or more in REP compared to naturally occurring fibroin.
  • substitution, deletion, insertion and / or addition of one or more amino acid residues as compared with naturally occurring fibroin There may be amino acid sequence modifications corresponding to the above.
  • the fifth modified fibroin is obtained by removing one or more hydrophilic amino acid residues (for example, amino acid residues having a negative hydrophobicity index) in the REP from the cloned natural fibroin gene sequence. It can be obtained by substituting a group (for example, an amino acid residue having a positive hydrophobicity index) and / or inserting one or more hydrophobic amino acid residues in REP.
  • hydrophilic amino acid residues for example, amino acid residues having a negative hydrophobicity index
  • a group for example, an amino acid residue having a positive hydrophobicity index
  • one or more hydrophilic amino acid residues in REP are substituted with hydrophobic amino acid residues from the amino acid sequence of naturally occurring fibroin, and / or one or more hydrophobic amino acid residues in REP It can also be obtained by designing an amino acid sequence corresponding to insertion of, and chemically synthesizing a nucleic acid encoding the designed amino acid sequence.
  • one or more hydrophilic amino acid residues in REP have been replaced with hydrophobic amino acid residues from the amino acid sequence of naturally occurring fibroin and / or one or more hydrophobic amino acids in REP
  • the amino acid sequence corresponding to the substitution, deletion, insertion and / or addition of one or more amino acid residues may be further modified.
  • the fifth modified fibroin comprises a domain sequence represented by Formula 1: [(A) n motif-REP] m , and is located on the most C-terminal side (A) from the n motif to the C terminus of the domain sequence.
  • p is the total number of amino acid residues included in the region where the average value of the hydrophobicity index of four consecutive amino acid residues is 2.6 or more
  • (A) When the total number of amino acid residues contained in the sequence excluding the sequence from the n motif to the C terminus of the domain sequence, which is located at the most C-terminal side, from the domain sequence is q, p / q is 6 It may have an amino acid sequence that is 2% or more.
  • hydrophobicity index of amino acid residues As for the hydrophobicity index of amino acid residues, a known index (Hydropathy index: Kyte J, & Doolittle R (1982) “A simple method for displaying the hydropathic character of bio.p. 7”. 105-132). Specifically, the hydrophobicity index (hydropathic index, hereinafter also referred to as “HI”) of each amino acid is as shown in Table 1 below.
  • a sequence obtained by removing the sequence from the domain sequence represented by Formula 1: [(A) n motif-REP] m to the most C-terminal side from the domain (A) n motif to the C terminus of the domain sequence. (Hereinafter referred to as “array A”).
  • array A the average value of the hydrophobicity index of four consecutive amino acid residues is calculated.
  • the average value of the hydrophobicity index is obtained by dividing the total HI of each amino acid residue contained in the four consecutive amino acid residues by 4 (number of amino acid residues).
  • the average value of the hydrophobicity index is obtained for all four consecutive amino acid residues (each amino acid residue is used for calculating the average value 1 to 4 times). Next, a region where the average value of the hydrophobicity index of four consecutive amino acid residues is 2.6 or more is specified. Even if a certain amino acid residue corresponds to a plurality of “four consecutive amino acid residues whose average value of hydrophobicity index is 2.6 or more”, it should be included as one amino acid residue in the region. become.
  • the total number of amino acid residues contained in the region is p.
  • the total number of amino acid residues contained in sequence A is q.
  • the average value of the hydrophobicity index of four consecutive amino acid residues is 2
  • p / q is preferably 6.2% or more, more preferably 7% or more, further preferably 10% or more, and preferably 20% or more. Even more preferably, it is still more preferably 30% or more.
  • the upper limit of p / q is not particularly limited, but may be 45% or less, for example.
  • the fifth modified fibroin is, for example, one or a plurality of hydrophilic amino acid residues (for example, a hydrophobicity index) in the REP so that the amino acid sequence of the naturally-derived fibroin thus cloned satisfies the above p / q condition. Is replaced with a hydrophobic amino acid residue (for example, an amino acid residue with a positive hydrophobicity index) and / or one or more hydrophobic amino acid residues are inserted in the REP By doing so, it can be obtained by locally modifying the amino acid sequence to include a region having a large hydrophobicity index.
  • hydrophilic amino acid residues for example, a hydrophobicity index
  • an amino acid sequence satisfying the above p / q conditions can be designed from the amino acid sequence of naturally derived fibroin, and a nucleic acid encoding the designed amino acid sequence can be obtained by chemical synthesis.
  • one or more amino acid residues in REP were replaced with amino acid residues having a higher hydrophobicity index and / or one or more amino acid residues in REP.
  • modifications corresponding to substitution, deletion, insertion and / or addition of one or more amino acid residues may be performed. .
  • the amino acid residue having a large hydrophobicity index is not particularly limited, but isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), methionine (M) and alanine (A ) are preferred, and valine (V), leucine (L) and isoleucine (I) are more preferred.
  • modified fibroin As specific examples of the fifth modified fibroin, (5-i) the amino acid sequence represented by SEQ ID NO: 19, SEQ ID NO: 20 or SEQ ID NO: 21, or (5-ii) SEQ ID NO: 19, SEQ ID NO: 20 or SEQ ID NO: Mention may be made of modified fibroin comprising an amino acid sequence having a sequence identity of 90% or more with the amino acid sequence shown in FIG.
  • the modified fibroin (5-i) will be described.
  • the amino acid sequence represented by SEQ ID NO: 22 is an amino acid sequence in which alanine residues in the (A) n motif of (A) naturally derived fibroin are deleted so that the number of consecutive alanine residues is five.
  • the amino acid sequence represented by SEQ ID NO: 19 has two amino acid sequences (VLI) each consisting of 3 amino acid residues inserted into every other REP with respect to the amino acid sequence represented by SEQ ID NO: 22, and represented by SEQ ID NO: 22. A part of amino acids on the C-terminal side are deleted so that the molecular weight of the amino acid sequence is almost the same.
  • the amino acid sequence represented by SEQ ID NO: 23 is obtained by inserting two alanine residues to the C-terminal side of each (A) n motif with respect to the amino acid sequence represented by SEQ ID NO: 22, and further adding some glutamine (Q) residues. A group is substituted with a serine (S) residue, and a part of amino acids on the C-terminal side is deleted so as to be approximately the same as the molecular weight of the amino acid sequence represented by SEQ ID NO: 22.
  • the amino acid sequence represented by SEQ ID NO: 20 is obtained by inserting one amino acid sequence (VLI) consisting of 3 amino acid residues every other REP to the amino acid sequence represented by SEQ ID NO: 23.
  • the amino acid sequence shown in SEQ ID NO: 21 is obtained by inserting two amino acid sequences (VLI) each consisting of 3 amino acid residues into the amino acid sequence shown in SEQ ID NO: 23 every other REP.
  • the modified fibroin (5-i) may be composed of the amino acid sequence represented by SEQ ID NO: 19, SEQ ID NO: 20 or SEQ ID NO: 21.
  • the modified fibroin (5-ii) comprises an amino acid sequence having 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 19, SEQ ID NO: 20 or SEQ ID NO: 21.
  • the modified fibroin of (5-ii) is also a protein containing a domain sequence represented by Formula 1: [(A) n motif-REP] m .
  • the sequence identity is preferably 95% or more.
  • the modified fibroin of (5-ii) has a sequence identity of 90% or more with the amino acid sequence represented by SEQ ID NO: 19, SEQ ID NO: 20 or SEQ ID NO: 21, and is located on the most C-terminal side (A) n
  • the amino acids included in the region where the average value of the hydrophobicity index of 4 consecutive amino acid residues is 2.6 or more P is the total number of residues
  • P / q is preferably 6.2% or more.
  • the fifth modified fibroin may contain a tag sequence at one or both of the N-terminal and C-terminal.
  • modified fibroin containing a tag sequence (-iii) the amino acid sequence represented by SEQ ID NO: 24, SEQ ID NO: 25 or SEQ ID NO: 26, or (5-iv) SEQ ID NO: 24, sequence Mention may be made of modified fibroin comprising an amino acid sequence having 90% or more sequence identity with the amino acid sequence shown in No. 25 or SEQ ID No. 26.
  • amino acid sequences represented by SEQ ID NO: 24, SEQ ID NO: 25, and SEQ ID NO: 26 are the amino acid sequences represented by SEQ ID NO: 12 at the N-terminus of the amino acid sequences represented by SEQ ID NO: 19, SEQ ID NO: 20 and SEQ ID NO: 21, respectively (His tag Including a sequence and a hinge sequence).
  • the modified fibroin may consist of the amino acid sequence represented by SEQ ID NO: 24, SEQ ID NO: 25 or SEQ ID NO: 26.
  • the modified fibroin (5-iv) includes an amino acid sequence having 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 24, SEQ ID NO: 25 or SEQ ID NO: 26.
  • the modified fibroin of (5-iv) is also a protein containing a domain sequence represented by Formula 1: [(A) n motif-REP] m .
  • the sequence identity is preferably 95% or more.
  • the modified fibroin (5-iv) has 90% or more sequence identity with the amino acid sequence represented by SEQ ID NO: 24, SEQ ID NO: 25 or SEQ ID NO: 26, and is located at the most C-terminal side (A) n
  • the amino acids included in the region where the average value of the hydrophobicity index of 4 consecutive amino acid residues is 2.6 or more P is the total number of residues
  • P / q is preferably 6.2% or more.
  • the fifth modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host.
  • the sequence of the secretion signal can be appropriately set according to the type of host.
  • the modified fibroin having a domain sequence in which the content of glutamine residues is reduced (sixth modified fibroin) has an amino acid sequence in which the content of glutamine residues is reduced compared to naturally occurring fibroin.
  • the sixth modified fibroin preferably contains at least one motif selected from GGX motif and GPGXX motif in the amino acid sequence of REP.
  • the content ratio of the GPGXX motif is usually 1% or more, may be 5% or more, and is preferably 10% or more.
  • the upper limit of GPGXX motif content rate 50% or less may be sufficient and 30% or less may be sufficient.
  • the “GPGXX motif content” is a value calculated by the following method.
  • Formula 1 [(A) n motif-REP] m or Formula 2: [(A) n motif-REP] m-
  • A) In the fibroin containing the domain sequence represented by the n motif, the most C-terminal side (A) In all REPs included in the sequence excluding the sequence from the n motif to the C-terminal of the domain sequence from the domain sequence, the total number of GPGXX motifs included in the region is tripled (ie, (Corresponding to the total number of G and P in the GPGXX motif) is defined as s, the sequence from the (A) n motif located at the most C-terminal side to the C-terminus of the domain sequence is excluded from the domain sequence, and (A) the n motif
  • the content ratio of GPGXX motif is calculated as s / t, where t is the total number of amino acid residues of all REPs removed.
  • “A sequence located at the most C-terminal side (A) excluding the sequence from the n motif to the C-terminal of the domain sequence from the domain sequence” (A)
  • the sequence from the n motif to the C terminus of the domain sequence ”(sequence corresponding to REP) may include a sequence that is not highly correlated with the sequence characteristic of fibroin, and m is small In this case (that is, when the domain sequence is short), the calculation result of the content ratio of the GPGXX motif is affected, so this influence is excluded.
  • the “GPGXX motif” is located at the C-terminus of REP, even if “XX” is, for example, “AA”, it is treated as “GPGXX motif”.
  • FIG. 3 is a schematic diagram showing the domain sequence of fibroin.
  • the calculation method of the content ratio of GPGXX motif will be specifically described with reference to FIG.
  • all REPs are “most C-terminally located ( A) GPGXX for calculating s because it is included in the “sequence excluding the sequence from the n motif to the C-terminal of the domain sequence from the domain sequence” (the sequence indicated by “region A” in FIG. 3).
  • the sixth modified fibroin preferably has a glutamine residue content of 9% or less, more preferably 7% or less, still more preferably 4% or less, and particularly preferably 0%. .
  • the “glutamine residue content” is a value calculated by the following method.
  • Formula 1 [(A) n motif-REP] m or Formula 2: [(A) n motif-REP] m- (A) In the fibroin containing the domain sequence represented by the n motif, the most C-terminal side Located in (A) all REPs included in the sequence (sequence corresponding to “region A” in FIG.
  • the total number of glutamine residues is u, the sequence from the (A) n- motif located at the most C-terminal side to the C-terminus of the domain sequence is removed from the domain sequence, and (A) the amino acid residues of all REPs excluding the n- motif
  • the glutamine residue content is calculated as u / t. In the calculation of the glutamine residue content rate, the reason why "A sequence located at the most C-terminal side (A) excluding the sequence from the n motif to the C-terminus of the domain sequence from the domain sequence" is the reason described above. It is the same.
  • the sixth modified fibroin corresponds to its domain sequence having one or more glutamine residues in REP deleted or replaced with other amino acid residues compared to naturally occurring fibroin. It may have an amino acid sequence.
  • the “other amino acid residue” may be an amino acid residue other than a glutamine residue, but is preferably an amino acid residue having a larger hydrophobicity index than the glutamine residue. Table 1 shows the hydrophobicity index of amino acid residues.
  • amino acid residues having a larger hydrophobicity index than glutamine residues include isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), methionine (M ) Amino acid residues selected from alanine (A), glycine (G), threonine (T), serine (S), tryptophan (W), tyrosine (Y), proline (P) and histidine (H). it can.
  • an amino acid residue selected from isoleucine (I), valine (V), leucine (L), phenylalanine (F), cysteine (C), methionine (M) and alanine (A) is more preferable. More preferred is an amino acid residue selected from among isoleucine (I), valine (V), leucine (L) and phenylalanine (F).
  • the hydrophobicity of REP is preferably ⁇ 0.8 or more, more preferably ⁇ 0.7 or more, still more preferably 0 or more, and 0.3 or more. It is still more preferable that it is and it is especially preferable that it is 0.4 or more.
  • the “hydrophobicity of REP” is a value calculated by the following method.
  • Formula 1 [(A) n motif-REP] m or Formula 2: [(A) n motif-REP] m- (A) In the fibroin containing the domain sequence represented by the n motif, the most C-terminal side (A) In all REPs included in the sequence (sequence corresponding to “region A” in FIG. 3) obtained by removing the sequence from the n motif to the C-terminal of the domain sequence from the domain sequence (each corresponding to “region A” in FIG.
  • each amino acid in the region Let v be the sum of the hydrophobicity indices of the residues, remove the sequence from the (A) n motif located at the most C-terminal side to the C-terminus of the domain sequence from the domain sequence, and (A) all REPs excluding the n motif
  • the hydrophobicity of REP is calculated as v / t, where t is the total number of amino acid residues.
  • the reason why “A sequence located at the most C-terminal side (A) excluding the sequence from the n motif to the C-terminal of the domain sequence from the domain sequence” is the reason described above. It is the same.
  • the sixth modified fibroin has its domain sequence deleted one or more glutamine residues in REP and / or one or more glutamine residues in REP compared to naturally occurring fibroin.
  • modifications corresponding to substitution of other amino acid residues there may also be amino acid sequence modifications corresponding to substitution, deletion, insertion and / or addition of one or more amino acid residues. .
  • the sixth modified fibroin is, for example, deleting one or more glutamine residues in REP from the cloned gene sequence of naturally occurring fibroin and / or other one or more glutamine residues in REP. It can obtain by substituting to the amino acid residue.
  • one or more glutamine residues in REP are deleted from the amino acid sequence of naturally occurring fibroin, and / or one or more glutamine residues in REP are replaced with other amino acid residues.
  • it can also be obtained by designing a corresponding amino acid sequence and chemically synthesizing a nucleic acid encoding the designed amino acid sequence.
  • the sixth modified fibroin (6-i) the amino acid sequence represented by SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32 or SEQ ID NO: 33
  • (6-ii) the amino acid sequence represented by SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32 or SEQ ID NO: 33 and 90% or more of the sequence Mention may be made of modified fibroin comprising amino acid sequences having identity.
  • the (6-i) modified fibroin will be described.
  • the amino acid sequence shown in SEQ ID NO: 7 is based on the base sequence and amino acid sequence of Nephila clapes (GenBank accession numbers: P46804.1, GI: 1174415), which is a naturally occurring fibroin, based on (A) n
  • the amino acid sequence in which the alanine residue in the motif is continued is modified with an amino acid to improve productivity, such as the number of consecutive alanine residues is five.
  • Met-PRT410 since Met-PRT410 has not altered the glutamine residue (Q), the glutamine residue content is comparable to the glutamine residue content of naturally occurring fibroin.
  • the amino acid sequence (M_PRT888) represented by SEQ ID NO: 27 is obtained by replacing all QQs in Met-PRT410 (SEQ ID NO: 7) with VL.
  • the amino acid sequence represented by SEQ ID NO: 28 (M_PRT965) is obtained by substituting all QQs in Met-PRT410 (SEQ ID NO: 7) with TS and replacing the remaining Q with A.
  • the amino acid sequence (M_PRT889) shown in SEQ ID NO: 29 is obtained by substituting all QQs in Met-PRT410 (SEQ ID NO: 7) with VL and replacing the remaining Q with I.
  • the amino acid sequence represented by SEQ ID NO: 30 (M_PRT916) is obtained by substituting all QQs in Met-PRT410 (SEQ ID NO: 7) with VI and replacing the remaining Q with L.
  • the amino acid sequence (M_PRT918) represented by SEQ ID NO: 31 is obtained by replacing all QQs in Met-PRT410 (SEQ ID NO: 7) with VF and replacing the remaining Q with I.
  • the amino acid sequence (M_PRT525) represented by SEQ ID NO: 34 is obtained by inserting two alanine residues into a region (A 5 ) where alanine residues are continuous with respect to Met-PRT410 (SEQ ID NO: 7).
  • the two C-terminal domain sequences were deleted and 13 glutamine residues (Q) were replaced with serine residues (S) or proline residues (P) so that they were almost the same as those in FIG.
  • the amino acid sequence (M_PRT699) represented by SEQ ID NO: 32 is obtained by substituting VL for all QQs in M_PRT525 (SEQ ID NO: 34).
  • the amino acid sequence (M_PRT698) represented by SEQ ID NO: 33 is obtained by substituting all QQs in M_PRT525 (SEQ ID NO: 34) with VL and replacing the remaining Q with I.
  • amino acid sequences represented by SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32 and SEQ ID NO: 33 all have a glutamine residue content of 9% or less (Table 2). ).
  • the modified fibroin (6-i) may be composed of the amino acid sequence represented by SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32 or SEQ ID NO: 33. .
  • the modified fibroin of (6-ii) has a sequence identity of 90% or more with the amino acid sequence represented by SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32 or SEQ ID NO: 33
  • the amino acid sequence having The modified fibroin of (6-ii) is also represented by the formula 1: [(A) n motif-REP] m or the formula 2: [(A) n motif-REP] m- (A) n motif.
  • the sequence identity is preferably 95% or more.
  • the modified fibroin (6-ii) preferably has a glutamine residue content of 9% or less.
  • the modified fibroin (6-ii) preferably has a GPGXX motif content of 10% or more.
  • the sixth modified fibroin may contain a tag sequence at one or both of the N-terminal and C-terminal. This makes it possible to isolate, immobilize, detect and visualize the modified fibroin.
  • modified fibroin containing the tag sequence (6-iii) SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40 or SEQ ID NO: 41
  • a modified fibroin comprising the amino acid sequence shown or (6-iv) SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40 or SEQ ID NO: 41 and 90 Mention may be made of modified fibroin comprising an amino acid sequence having a sequence identity of at least%.
  • amino acid sequences represented by SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, and SEQ ID NO: 41 are SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, respectively.
  • the amino acid sequence represented by SEQ ID NO: 12 (including His tag sequence and hinge sequence) is added to the N-terminus of the amino acid sequence represented by SEQ ID NO: 31, SEQ ID NO: 32 and SEQ ID NO: 33.
  • the modified fibroin of (6-iii) may be composed of the amino acid sequence represented by SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, or SEQ ID NO: 41. .
  • the modified fibroin of (6-iv) has a sequence identity of 90% or more with the amino acid sequence represented by SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40 or SEQ ID NO: 41.
  • the amino acid sequence having The modified fibroin of (6-iv) is also a domain represented by Formula 1: [(A) n motif-REP] m or Formula 2: [(A) n motif-REP] m- (A) n motif.
  • the sequence identity is preferably 95% or more.
  • the modified fibroin (6-iv) preferably has a glutamine residue content of 9% or less.
  • the modified fibroin (6-iv) preferably has a GPGXX motif content of 10% or more.
  • the sixth modified fibroin may contain a secretion signal for releasing the protein produced in the recombinant protein production system to the outside of the host.
  • the sequence of the secretion signal can be appropriately set according to the type of host.
  • the modified fibroin according to the present embodiment is characterized in that the first modified fibroin, the second modified fibroin, the third modified fibroin, the fourth modified fibroin, the fifth modified fibroin, and the sixth modified fibroin Alternatively, it may be a modified fibroin having at least two or more characteristics.
  • Fibroin is obtained by, for example, expressing the nucleic acid by a host transformed with an expression vector having a nucleic acid sequence encoding the fibroin and one or more regulatory sequences operably linked to the nucleic acid sequence. Can be produced.
  • the method for producing a nucleic acid encoding fibroin is not particularly limited. For example, using a gene encoding natural fibroin, amplified and cloned by polymerase chain reaction (PCR) or the like, modified by genetic engineering techniques as necessary, or chemically synthesized, The nucleic acid can be produced.
  • the method for chemically synthesizing nucleic acids is not particularly limited. For example, AKTA oligopilot plus 10/100 (GE Healthcare Japan Co., Ltd.) is used based on the amino acid sequence information of proteins obtained from the NCBI web database.
  • a gene can be chemically synthesized by a method of linking oligonucleotides that are synthesized automatically by PCR or the like.
  • a nucleic acid encoding fibroin consisting of an amino acid sequence in which an amino acid sequence consisting of a start codon and a His10 tag is added to the N-terminus of the above amino acid sequence is synthesized. Also good.
  • the regulatory sequence is a sequence that controls the expression of fibroin in the host (for example, promoter, enhancer, ribosome binding sequence, transcription termination sequence, etc.), and can be appropriately selected according to the type of host.
  • a promoter an inducible promoter that functions in a host cell and can induce expression of fibroin may be used.
  • An inducible promoter is a promoter that can control transcription by the presence of an inducer (expression inducer), absence of a repressor molecule, or physical factors such as an increase or decrease in temperature, osmotic pressure or pH value.
  • the type of expression vector can be appropriately selected according to the type of host, such as a plasmid vector, virus vector, cosmid vector, fosmid vector, artificial chromosome vector, and the like.
  • a vector that can replicate autonomously in a host cell or can be integrated into a host chromosome and contains a promoter at a position where a nucleic acid encoding fibroin can be transcribed is preferably used.
  • any of prokaryotes and eukaryotes such as yeast, filamentous fungi, insect cells, animal cells and plant cells can be preferably used.
  • prokaryotic hosts include bacteria belonging to the genus Escherichia, Brevibacillus, Serratia, Bacillus, Microbacterium, Brevibacterium, Corynebacterium, Pseudomonas and the like.
  • microorganisms belonging to the genus Escherichia include Escherichia coli.
  • microorganisms belonging to the genus Brevibacillus include Brevibacillus agri and the like.
  • microorganisms belonging to the genus Serratia include Serratia liqufaciens and the like.
  • microorganisms belonging to the genus Bacillus include Bacillus subtilis.
  • microorganisms belonging to the genus Microbacterium include microbacterium / ammonia film.
  • microorganisms belonging to the genus Brevibacterium include Brevibacterium divaricatam.
  • microorganisms belonging to the genus Corynebacterium include Corynebacterium ammoniagenes.
  • microorganisms belonging to the genus Pseudomonas include Pseudomonas putida.
  • vectors for introducing a nucleic acid encoding fibroin include, for example, pBTrp2 (manufactured by Boehringer Mannheim), pGEX (manufactured by Pharmacia), pUC18, pBluescriptII, pSupex, pET22b, pCold, pNCO2 (Japanese Patent Laid-Open No. 2002-238696) and the like.
  • Examples of eukaryotic hosts include yeast and filamentous fungi (molds, etc.).
  • yeast include yeasts belonging to the genus Saccharomyces, Pichia, Schizosaccharomyces and the like.
  • Examples of the filamentous fungi include filamentous fungi belonging to the genus Aspergillus, the genus Penicillium, the genus Trichoderma and the like.
  • examples of a vector into which a nucleic acid encoding fibroin is introduced include YEp13 (ATCC37115) and YEp24 (ATCC37051).
  • a method for introducing the expression vector into the host cell any method can be used as long as it is a method for introducing DNA into the host cell.
  • a method using calcium ions [Proc. Natl. Acad. Sci. USA, 69, 2110 (1972)]
  • electroporation method electroporation method
  • spheroplast method protoplast method
  • lithium acetate method competent method, and the like.
  • a method for expressing a nucleic acid by a host transformed with an expression vector in addition to direct expression, secretory production, fusion protein expression, etc. can be performed according to the method described in Molecular Cloning 2nd edition, etc. .
  • Fibroin can be produced, for example, by culturing a host transformed with an expression vector in a culture medium, producing and accumulating the protein in the culture medium, and collecting the protein from the culture medium.
  • the method for culturing a host in a culture medium can be performed according to a method usually used for culturing a host.
  • the culture medium contains a carbon source, nitrogen source, inorganic salts, etc. that can be assimilated by the host, and can efficiently culture the host. If so, either a natural medium or a synthetic medium may be used.
  • Any carbon source may be used as long as it can be assimilated by the above-mentioned transformed microorganism.
  • Examples thereof include glucose, fructose, sucrose, and carbohydrates such as molasses, starch and starch hydrolyzate, acetic acid and propionic acid, etc.
  • Organic acids and alcohols such as ethanol and propanol can be used.
  • the nitrogen source examples include ammonium salts of inorganic acids or organic acids such as ammonia, ammonium chloride, ammonium sulfate, ammonium acetate, and ammonium phosphate, other nitrogen-containing compounds, and peptone, meat extract, yeast extract, corn steep liquor, Casein hydrolyzate, soybean meal and soybean meal hydrolyzate, various fermented cells and digested products thereof can be used.
  • inorganic salts for example, monopotassium phosphate, dipotassium phosphate, magnesium phosphate, magnesium sulfate, sodium chloride, ferrous sulfate, manganese sulfate, copper sulfate and calcium carbonate can be used.
  • Cultivation of prokaryotes such as E. coli or eukaryotes such as yeast can be performed under aerobic conditions such as shaking culture or deep aeration and agitation culture.
  • the culture temperature is, for example, 15 to 40 ° C.
  • the culture time is usually 16 hours to 7 days.
  • the pH of the culture medium during the culture is preferably maintained at 3.0 to 9.0.
  • the pH of the culture medium can be adjusted using an inorganic acid, an organic acid, an alkaline solution, urea, calcium carbonate, ammonia, or the like.
  • antibiotics such as ampicillin and tetracycline may be added to the culture medium as necessary.
  • an inducer may be added to the medium as necessary.
  • isopropyl- ⁇ -D-thiogalactopyranoside is used when cultivating a microorganism transformed with an expression vector using the lac promoter
  • indole acrylic is used when culturing a microorganism transformed with an expression vector using the trp promoter.
  • An acid or the like may be added to the medium.
  • Isolation and purification of the expressed fibroin can be performed by a commonly used method.
  • the host cell is recovered by centrifugation after culturing, suspended in an aqueous buffer, and then subjected to an ultrasonic crusher, a French press, a Manton Gaurin.
  • the host cells are disrupted with a homogenizer, dynomill, or the like to obtain a cell-free extract.
  • a method usually used for protein isolation and purification that is, a solvent extraction method, a salting-out method using ammonium sulfate, a desalting method, an organic solvent, etc.
  • Precipitation method anion exchange chromatography method using resin such as diethylaminoethyl (DEAE) -Sepharose, DIAION HPA-75 (manufactured by Mitsubishi Kasei), positive using resin such as S-Sepharose FF (manufactured by Pharmacia)
  • Electrophoresis methods such as ion exchange chromatography, hydrophobic chromatography using resins such as butyl sepharose and phenyl sepharose, gel filtration using molecular sieve, affinity chromatography, chromatofocusing, isoelectric focusing Using methods such as these alone or in combination, purification It is possible to obtain the goods.
  • fibroin when fibroin is expressed by forming an insoluble substance in the cell, the host cell is similarly collected, crushed, and centrifuged to recover the fibroin insoluble substance as a precipitate fraction.
  • the recovered insoluble matter of fibroin can be solubilized with a protein denaturant.
  • a purified fibroin preparation can be obtained by the same isolation and purification method as described above.
  • the fibroin when the fibroin is secreted extracellularly, the fibroin can be recovered from the culture supernatant. That is, a culture supernatant is obtained by treating the culture with a technique such as centrifugation, and a purified preparation can be obtained from the culture supernatant by using the same isolation and purification method as described above.
  • the content of fibroin contained in the solution of the present embodiment may be, for example, 0.01 to 50 w / v%, preferably 0.05 to 40 w / v%, based on the total amount of the solution. More preferably, it is 1 to 20 w / v%, even more preferably 0.25 to 10 w / v%, and even more preferably 0.5 to 5 w / v%.
  • the solution of this embodiment is various polymers, such as surfactant, an electroconductive or nonelectroconductive polymer (The said polymer contains proteins other than fibroin), for example. Materials and the like may be included as other additives. Moreover, content of an additive can be added in the range which does not inhibit the effect of this invention.
  • the carbon nanotube dispersion liquid (CNT dispersion liquid) of the present invention contains CNT and the CNT dispersant of the present embodiment described above.
  • the dispersion is a liquid in which the obtained composition is visually free of precipitates and / or aggregates and, after standing at least for 24 hours, is visually free of precipitates and / or aggregates.
  • the CNT dispersion of the present invention is excellent in CNT dispersibility, it is possible to produce a matrix material in which CNTs are well dispersed, and the characteristics of the matrix can be controlled efficiently. Therefore, the CNT dispersion liquid of the present invention is suitably used for the production of composite materials containing CNTs, for example.
  • the CNT dispersion is prepared using CNT and the CNT dispersant of the present embodiment.
  • the CNT dispersion may be in liquid form or semi-solid like a paste or gel, but is preferably in liquid form.
  • the CNT dispersion is, for example, a CNT and the CNT dispersant of the present embodiment mixed and dispersed (for example, a ball mill, a bead mill, a sand mill, a roll mill, a homogenizer, an ultrasonic homogenizer, a high-pressure homogenizer, an ultrasonic device, an attritor, It can be prepared by mixing using a dissolver, paint shaker, or the like.
  • the CNT content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 4 parts by mass or less with respect to 100 parts by mass of fibroin. It is still more preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less.
  • Dispersion method of carbon nanotube The present invention described above can also be regarded as a carbon nanotube dispersion method including mixing a CNT dispersant and CNTs. Preferred embodiments of the dispersion method are as described above.
  • a modified spider silk fibroin having the amino acid sequence represented by SEQ ID NO: 15 was designed based on the base sequence and amino acid sequence of Nephila clavies (GenBank accession numbers: P46804.1, GI: 1174415), which is a naturally occurring fibroin.
  • Amino acid sequence shown in SEQ ID NO: 9 is a fibroin naturally occurring Nephila clavipes (GenBank accession number: P46804.1, GI: 1174415) based on the nucleotide sequence and amino acid sequence of, (A) n Productivity such as making the number of consecutive alanine residues an amino acid sequence in which the alanine residues in the motif are continuous, adding the amino acid sequence shown in SEQ ID NO: 42 (hinge sequence and His tag) to the C-terminus, etc. The amino acid was modified to improve the quality.
  • the amino acid sequence represented by SEQ ID NO: 15 is obtained by adding the amino acid sequence represented by SEQ ID NO: 12 (amino acid sequence including His tag sequence and hinge sequence) to the N-terminus of Met-PRT799.
  • a nucleic acid encoding a protein having the amino acid sequence represented by SEQ ID NO: 15 was synthesized. The nucleic acid was added with an NdeI site at the 5 'end and an EcoRI site downstream of the stop codon. These five types of nucleic acids were cloned into a cloning vector (pUC118). Thereafter, the nucleic acid was cleaved by restriction enzyme treatment with NdeI and EcoRI, and then recombined with the protein expression vector pET-22b (+) to obtain an expression vector.
  • Escherichia coli BLR (DE3) was transformed with a pET22b (+) expression vector containing a nucleic acid encoding a protein having the amino acid sequence represented by SEQ ID NO: 15.
  • the transformed Escherichia coli was cultured in 2 mL of LB medium containing ampicillin for 15 hours.
  • the culture solution was added to 100 mL of a seed culture medium (Table 4) containing ampicillin so that the OD 600 was 0.005.
  • the culture temperature was kept at 30 ° C., and flask culture was performed until the OD 600 reached 5 (about 15 hours) to obtain a seed culture solution.
  • the seed culture was added to a jar fermenter to which 500 mL of production medium (Table 5) was added so that the OD 600 was 0.05, and transformed E. coli was inoculated.
  • the culture solution temperature was maintained at 37 ° C., and the culture was performed at a constant pH of 6.9. Further, the dissolved oxygen concentration in the culture solution was maintained at 20% of the dissolved oxygen saturation concentration.
  • a feed solution (glucose 455 g / 1 L, Yeast Extract 120 g / 1 L) was added at a rate of 1 mL / min.
  • the culture solution temperature was maintained at 37 ° C., and the culture was performed at a constant pH of 6.9.
  • the dissolved oxygen concentration in the culture solution was maintained at 20% of the dissolved oxygen saturation concentration, and cultured for 20 hours.
  • 1M isopropyl- ⁇ -thiogalactopyranoside (IPTG) was added to the culture solution to a final concentration of 1 mM to induce expression of the target protein.
  • the culture solution was centrifuged, and the cells were collected. SDS-PAGE was performed using cells prepared from the culture solution before and after the addition of IPTG, and the expression of the target protein was confirmed by the appearance of a band of the desired protein size depending on the addition of IPTG.
  • the washed precipitate was suspended in 8M guanidine buffer (8M guanidine hydrochloride, 10 mM sodium dihydrogen phosphate, 20 mM NaCl, 1 mM Tris-HCl, pH 7.0) to a concentration of 100 mg / mL, and 60 ° C. And stirred for 30 minutes with a stirrer to dissolve. After dissolution, dialysis was performed with water using a dialysis tube (cellulose tube 36/32 manufactured by Sanko Junyaku Co., Ltd.). The white aggregated protein obtained after dialysis was recovered by centrifugation, the water was removed with a freeze dryer, and the lyophilized powder was recovered.
  • 8M guanidine buffer 8M guanidine hydrochloride, 10 mM sodium dihydrogen phosphate, 20 mM NaCl, 1 mM Tris-HCl, pH 7.0
  • test solution (1) (Example 1) The above-mentioned lyophilized powder of PRT799 protein was added to dimethyl sulfoxide (DMSO) so as to have a concentration of 1.0% by mass, dissolved at 40 ° C. over 1 hour, and the test solution of Example 1 (CNT dispersant). Got.
  • DMSO dimethyl sulfoxide
  • Example 2 The above-mentioned freeze-dried powder of PRT799 protein and LiCl as an inorganic salt were added to DMSO so as to have concentrations of 1.0% by mass and 4.0% by mass, respectively, and dissolved at 40 ° C. for 1 hour.
  • the test liquid (CNT dispersant) of Example 2 was obtained.
  • Comparative Example 2 A powder of lysozyme (derived from egg white, manufactured by Wako Pure Chemical Industries, Ltd.) was added to DMSO so as to have a concentration of 1.0% by mass and dissolved at 40 ° C. over 1 hour to obtain a test solution of Comparative Example 2. .
  • CNT single-walled carbon nanotubes MEIJO eDIPS, manufactured by Meijo Nanocarbon Co., Ltd.
  • CNT single-walled carbon nanotubes MEIJO eDIPS, manufactured by Meijo Nanocarbon Co., Ltd.
  • the evaluation criteria for dispersibility are as follows.
  • FIG. 4 is a photograph showing the appearance of each test solution when evaluating CNT dispersibility.
  • the test solutions of Comparative Example 1, Comparative Example 2, Example 1, and Example 2 are arranged from left to right.
  • Example 2-1 The PRT799 protein lyophilized powder described above was added to hexafluoro-2-propanol (HFIP) to a concentration of 0.1 w / v%, and dissolved at 40 ° C. over 1 hour. A test liquid (CNT dispersant) was obtained.
  • HFIP hexafluoro-2-propanol
  • Example 2-2 The above-mentioned freeze-dried PRT799 protein powder was added to HFIP to a concentration of 1.0 w / v%, dissolved at 40 ° C. over 1 hour, and the test liquid (CNT dispersant) of Example 2-2 was dissolved. Obtained.
  • FIG. 5 is a photograph showing the appearance of each test solution when evaluating CNT dispersibility.
  • the test solutions of Comparative Example 2-1, Example 2-1, and Example 2-2 are arranged from left to right.
  • Example 2-1 In the test solution of Comparative Example 2-1 containing only the solvent (HFIP), CNT aggregated and could not be dispersed.
  • CNT dispersant In the test liquid (CNT dispersant) of Example 2-2 in which 1.0 w / v% PRT799 was dissolved in HFIP as a solute, CNT was well dispersed. Even in the test solution (CNT dispersant) of Example 2-1 in which the solute concentration was reduced to 0.1 w / v%, the dispersibility of CNT was maintained.

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Abstract

La présente invention concerne un dispersant de nanotubes de carbone qui est composé d'une solution qui contient une fibroïne et un solvant.
PCT/JP2019/003477 2018-01-31 2019-01-31 Dispersant de nanotubes de carbone, liquide de dispersion de nanotubes de carbone et procédé de dispersion de nanotubes de carbone WO2019151435A1 (fr)

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WO2021065812A1 (fr) * 2019-09-30 2021-04-08 Ｓｐｉｂｅｒ株式会社 Liquide dopant et procédé de production d'un article moulé en fibroïne modifiée l'utilisant
CN113087948A (zh) * 2021-04-21 2021-07-09 哈尔滨工业大学（深圳） 薄膜及其制备方法
CN113437632A (zh) * 2021-05-10 2021-09-24 深圳技术大学 一种碳纳米管饱和吸收体及激光装置

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