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31 results on '"Himiyama, Tomoki"'

1. Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity.

Author

Kagawa, Yoshiyuki, Oohora, Koji, Himiyama, Tomoki, Suzuki, Akihiro, and Hayashi, Takashi

Subjects
IRON porphyrins, HEMOPROTEINS, REDUCTION potential, CYCLOPROPANATION, METALLOENZYMES, MYOGLOBIN
Abstract

Design of metal cofactor ligands is essential for controlling the reactivity of metalloenzymes. We investigated a carbene transfer reaction catalyzed by myoglobins containing iron porphyrin cofactors with one and two trifluoromethyl groups at peripheral sites (FePorCF3 and FePor(CF3)2, respectively), native heme and iron porphycene (FePc). These four myoglobins show a wide range of Fe(II)/Fe(III) redox potentials in the protein of +147 mV, +87 mV, +42 mV and −198 mV vs. NHE, respectively. Myoglobin reconstituted with FePor(CF3)2 has a more positive potential, which enhances the reactivity of a carbene intermediate with alkenes, and demonstrates superior cyclopropanation of inert alkenes, such as aliphatic and internal alkenes. In contrast, engineered myoglobin reconstituted with FePc has a more negative redox potential, which accelerates the formation of the intermediate, but has low reactivity for inert alkenes. Mechanistic studies indicate that myoglobin with FePor(CF3)2 generates an undetectable active intermediate with a radical character. In contrast, this reaction catalyzed by myoglobin with FePc includes a detectable iron–carbene species with electrophilic character. This finding highlights the importance of redox‐focused design of the iron porphyrinoid cofactor in hemoproteins to tune the reactivity of the carbene transfer reaction. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Crystal Structure of the Native Chromoprotein from Pleurotus salmoneostramineusProvides Insights into the Pigmentation Mechanism

Author

Ihara, Makoto, Tsuchida, Noriko, Sumida, Marina, Himiyama, Tomoki, Kitayama, Takashi, Shirasaka, Norifumi, and Fukuta, Yasuhisa

Abstract

The pink-colored protein from the fungus Pleurotus salmoneostramineus(PsPCP) possesses unusual primary sequences with little resemblance to those of known proteins and exhibits a red color in aqueous solution. To understand the pigmentation mechanism of PsPCP, we elucidated the X-ray crystal structure of the native PsPCP. We identified a highly conjugated polyene ligand 2-dehydro-3-deoxylaetiporic acid A as a chromophore ligand, whose solution exhibits yellow. The crystal structure of PsPCP indicated that the ligand is secured in the central cavity and anchored at both termini by hydrophilic interactions and that surrounding residues show CH-pi and C–H···O hydrogen bondings. Geometrical analyses of the bound ligand demonstrated that the conjugated C–C and C═C bonds exhibit similar bond distances. The result indicated enhanced electron delocalization within the conjugated CC bond system, resulting in a redshift of the chromophore ligand. The computational estimates of the UV-vis spectra support the view that the electron delocalization within the conjugated CC bonds system of the bound ligand, induced by the specific ligand geometry within a limited space of PsPCP cavity, is responsible for the red pigmentation of PsPCP. Thus, we propose that the coloring mechanism of PsPCP, which constrains the geometry of a highly conjugated polyene ligand, is a novel type of pigment chemistry.

Published
2024
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8. Titelbild: Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity (Angew. Chem. 36/2024).

Author

Kagawa, Yoshiyuki, Oohora, Koji, Himiyama, Tomoki, Suzuki, Akihiro, and Hayashi, Takashi

Subjects
PLASTIC scrap, REDUCTION potential, SCISSION (Chemistry), LACTIC acid, OXYGEN reduction
Abstract

The article titled "Titelbild: Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity" in Angewandte Chemie discusses the use of myoglobins reconstituted with artificial cofactors to demonstrate catalytic cyclopropanation reactions. The cover image depicts protein-based trucks carrying rice ears to produce rice sacks, representing the catalysis process. Another article in the journal discusses a novel NiCoMoS-Ti3C2Tx core-shell fiber for high-performance electrochemical supercapacitors. Additionally, there is a report on a four-electron oxygen reduction reaction electrocatalyst and a process for transforming waste PET plastics into lactic acid. Lastly, a study on doping-induced kernel insertion in Cu(I) nanoclusters is presented, revealing the creation of new types of copper-silver alloy nanoclusters. [Extracted from the article]

Published
2024
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23. Unnaturally Distorted Hexagonal Protein Ring Alternatingly Reorganized from Two Distinct Chemically Modified Proteins

Author

Himiyama, Tomoki, Hamaguchi, Tasuku, Yonekura, Koji, and Nakamura, Tsutomu

Abstract

In this study, we constructed a semiartificial protein assembly of alternating ring type, which was modified from the natural assembly state via incorporation of a synthetic component at the protein interface. For the redesign of a natural protein assembly, a scrap-and-build approach employing chemical modification was used. Two different protein dimer units were designed based on peroxiredoxin from Thermococcus kodakaraensis, which originally forms a dodecameric hexagonal ring with six homodimers. The two dimeric mutants were reorganized into a ring by reconstructing the protein–protein interactions via synthetic naphthalene moieties introduced by chemical modification. Cryo-electron microscopy revealed the formation of a uniquely shaped dodecameric hexagonal protein ring with broken symmetry, distorted from the regular hexagon of the wild-type protein. The artificially installed naphthalene moieties were arranged at the interfaces of dimer units, forming two distinct protein–protein interactions, one of which is highly unnatural. This study deciphered the potential of the chemical modification technique that constructs semiartificial protein structures and assembly hardly accessible by conventional amino acid mutations.

Published
2024
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29. Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity

Author

Kagawa, Yoshiyuki, Oohora, Koji, Himiyama, Tomoki, Suzuki, Akihiro, Hayashi, Takashi, Kagawa, Yoshiyuki, Oohora, Koji, Himiyama, Tomoki, Suzuki, Akihiro, and Hayashi, Takashi

Abstract

Kagawa Y., Oohora K., Himiyama T., et al. Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity. Angewandte Chemie - International Edition, (2024); https://doi.org/10.1002/anie.202403485., Design of metal cofactor ligands is essential for controlling the reactivity of metalloenzymes. We investigated a carbene transfer reaction catalyzed by myoglobins containing iron porphyrin cofactors with one and two trifluoromethyl groups at peripheral sites (FePorCF₃ and FePor(CF₃)₂, respectively), native heme and iron porphycene (FePc). These four myoglobins show a wide range of Fe(II)/Fe(III) redox potentials in the protein of +147 mV, +87 mV, +42 mV and −198 mV vs. NHE, respectively. Myoglobin reconstituted with FePor(CF₃)₂ has a more positive potential, which enhances the reactivity of a carbene intermediate with alkenes, and demonstrates superior cyclopropanation of inert alkenes, such as aliphatic and internal alkenes. In contrast, engineered myoglobin reconstituted with FePc has a more negative redox potential, which accelerates the formation of the intermediate, but has low reactivity for inert alkenes. Mechanistic studies indicate that myoglobin with FePor(CF₃)₂ generates an undetectable active intermediate with a radical character. In contrast, this reaction catalyzed by myoglobin with FePc includes a detectable iron–carbene species with electrophilic character. This finding highlights the importance of redox-focused design of the iron porphyrinoid cofactor in hemoproteins to tune the reactivity of the carbene transfer reaction.

30. Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity

Author

Kagawa, Yoshiyuki, Oohora, Koji, Himiyama, Tomoki, Suzuki, Akihiro, Hayashi, Takashi, Kagawa, Yoshiyuki, Oohora, Koji, Himiyama, Tomoki, Suzuki, Akihiro, and Hayashi, Takashi

Abstract

Kagawa Y., Oohora K., Himiyama T., et al. Redox Engineering of Myoglobin by Cofactor Substitution to Enhance Cyclopropanation Reactivity. Angewandte Chemie - International Edition, (2024); https://doi.org/10.1002/anie.202403485., Design of metal cofactor ligands is essential for controlling the reactivity of metalloenzymes. We investigated a carbene transfer reaction catalyzed by myoglobins containing iron porphyrin cofactors with one and two trifluoromethyl groups at peripheral sites (FePorCF₃ and FePor(CF₃)₂, respectively), native heme and iron porphycene (FePc). These four myoglobins show a wide range of Fe(II)/Fe(III) redox potentials in the protein of +147 mV, +87 mV, +42 mV and −198 mV vs. NHE, respectively. Myoglobin reconstituted with FePor(CF₃)₂ has a more positive potential, which enhances the reactivity of a carbene intermediate with alkenes, and demonstrates superior cyclopropanation of inert alkenes, such as aliphatic and internal alkenes. In contrast, engineered myoglobin reconstituted with FePc has a more negative redox potential, which accelerates the formation of the intermediate, but has low reactivity for inert alkenes. Mechanistic studies indicate that myoglobin with FePor(CF₃)₂ generates an undetectable active intermediate with a radical character. In contrast, this reaction catalyzed by myoglobin with FePc includes a detectable iron–carbene species with electrophilic character. This finding highlights the importance of redox-focused design of the iron porphyrinoid cofactor in hemoproteins to tune the reactivity of the carbene transfer reaction.

31. A Pyrene-Linked Cavity within a β-Barrel Protein Promotes an Asymmetric Diels-Alder Reaction.

Author

Himiyama T, Taniguchi N, Kato S, Onoda A, and Hayashi T

Subjects
Aza Compounds chemistry, Catalysis, Copper chemistry, Cyclopentanes chemistry, Heme-Binding Proteins, Maleimides chemistry, Models, Molecular, Protein Conformation, beta-Strand, Arabidopsis chemistry, Arabidopsis Proteins chemistry, Cycloaddition Reaction methods, Hemeproteins chemistry, Pyrenes chemistry
Abstract

A unique π-expanded reaction cavity tethering a polycyclic moiety which provides a platform for substrate binding was constructed within the robust β-barrel structure of nitrobindin (NB). NB variants with cavities of different sizes and shapes are coupled with N-(1-pyrenyl)maleimide (Pyr) to prepare a series of NB-Pyr conjugates. The orientation of the pyrene moiety is fixed within the cavity by the coupling reaction. The fluorescent quenching analysis of NB-Pyr indicates that azachalcone (aza), which is a dienophile for a Diels-Alder (DA) reaction, is efficiently incorporated within the pyrene-linked reaction cavity by the aromatic interaction. The DA reaction between aza and cyclopentadiene proceeds within the reaction cavity of NB-Pyr in the presence of Cu II ion in high yield and high enantio- and regioselectivity., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2017
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