2021/10/21 更新

写真a

フジモト カズヒロ
藤本 和宏
FUJIMOTO Kazuhiro J.
所属
トランスフォーマティブ生命分子研究所 特任准教授
大学院担当
大学院理学研究科
職名
特任准教授

学位 1

  1. 博士(工学) ( 2007年3月   京都大学 ) 

現在の研究課題とSDGs 1

  1. 光合成アンテナ系における励起エネルギー移動機構の解明

 

論文 5

  1. Spectral Tuning Mechanism of Photosynthetic Light-Harvesting Complex II Revealed by Ab Initio Dimer Exciton Model 査読有り

    Fujimoto Kazuhiro J., Minoda Takumi, Yanai Takeshi

    JOURNAL OF PHYSICAL CHEMISTRY B   125 巻 ( 37 ) 頁: 10459 - 10470   2021年9月

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    記述言語:英語   出版者・発行元:Journal of Physical Chemistry B  

    Excited states of two kinds of bacteriochlorophyll (BChl) aggregates, B850 and B800, in photosynthetic light-harvesting complex II (LH2) are theoretically investigated by developing and using an extended exciton model considering efficiently evaluated excitonic coupling. Our exciton model based on dimer fragmentation is shown to reproduce the experimental absorption spectrum of LH2 with good accuracy, entailing their different redshifts originating from aggregations of B850 and B800. The systematic analysis has been performed on the spectra by quantitatively decomposing their spectral shift energies into the contributions of various effects: structural distortion, electrostatic, excitonic coupling, and charge-transfer (CT) effects. Our results show that the spectral redshift of B800 is mainly attributed to its electrostatic interaction with the protein environment, while that of B850 arises from the marked effect of the excitonic coupling between BChl units. The interchromophore CT excitation also plays a key role in the spectral redshift of B850. This CT effect can be effectively described using our dimer model. This suited characterization reveals that the pronounced CT effect originates from the characteristics of B850 that has closely spaced BChls as dimers. We highlight the importance of the refinement of the crystal structure with the use of quantum chemical methods for prediction of the spectrum.

    DOI: 10.1021/acs.jpcb.1c04457

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  2. Electronic Couplings and Electrostatic Interactions Behind the Light Absorption of Retinal Proteins 査読有り

    Fujimoto Kazuhiro J.

    FRONTIERS IN MOLECULAR BIOSCIENCES   8 巻   頁: 752700   2021年9月

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    記述言語:英語   出版者・発行元:Frontiers in Molecular Biosciences  

    The photo-functional chromophore retinal exhibits a wide variety of optical absorption properties depending on its intermolecular interactions with surrounding proteins and other chromophores. By utilizing these properties, microbial and animal rhodopsins express biological functions such as ion-transport and signal transduction. In this review, we present the molecular mechanisms underlying light absorption in rhodopsins, as revealed by quantum chemical calculations. Here, symmetry-adapted cluster-configuration interaction (SAC-CI), combined quantum mechanical and molecular mechanical (QM/MM), and transition-density-fragment interaction (TDFI) methods are used to describe the electronic structure of the retinal, the surrounding protein environment, and the electronic coupling between chromophores, respectively. These computational approaches provide successful reproductions of experimentally observed absorption and circular dichroism (CD) spectra, as well as insights into the mechanisms of unique optical properties in terms of chromophore-protein electrostatic interactions and chromophore-chromophore electronic couplings. On the basis of the molecular mechanisms revealed in these studies, we also discuss strategies for artificial design of the optical absorption properties of rhodopsins.

    DOI: 10.3389/fmolb.2021.752700

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  3. Excitonic coupling effect on the circular dichroism spectrum of sodium-pumping rhodopsin KR2 査読有り

    Fujimoto Kazuhiro J., Inoue Keiichi

    JOURNAL OF CHEMICAL PHYSICS   153 巻 ( 4 ) 頁: 045101   2020年7月

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    記述言語:英語   出版者・発行元:Journal of Chemical Physics  

    We investigate the role of excitonic coupling between retinal chromophores of Krokinobacter eikastus rhodopsin 2 (KR2) in the circular dichroism (CD) spectrum using an exciton model combined with the transition density fragment interaction (TDFI) method. Although the multimer formation of retinal protein commonly induces biphasic negative and positive CD bands, the KR2 pentamer shows only a single positive CD band. The TDFI calculation reveals the dominant contribution of the Coulomb interaction and negligible contributions of exchange and charge-transfer interactions to the excitonic coupling energy. The exciton model with TDFI successfully reproduces the main features of the experimental absorption and CD spectra of KR2, which allow us to investigate the mechanism of the CD spectral shape observed in the KR2 pentamer. The results clearly show that the red shift of the CD band is attributed to the excitonic coupling between retinal chromophores. Further analysis reveals that the weak excitonic coupling plays a crucial role in the shape of the CD spectrum. The present approach provides a basis for understanding the origin of the KR2 CD spectrum and is useful for analyzing the mechanism of chromophore-chromophore interactions in biological systems.

    DOI: 10.1063/5.0013642

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  4. Exciton-coupled Circular Dichroism-based Glucose and Galactose Selective Sensing in Aqueous Media with an Anthracene-appended Benzoxaborole Dimer 査読有り

    Kusano Shuhei, Ichikura Yuma, Fujimoto Kazuhiro J., Konishi Sae, Yamada Yuji, Hayashida Osamu

    CHEMISTRY LETTERS   49 巻 ( 7 ) 頁: 764 - 767   2020年7月

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    記述言語:英語   出版者・発行元:Chemistry Letters  

    We developed an anthracene-appended benzoxaborole dimer 1 and established selective sensing of D-glucose (Glc) and D-galactose (Gal) via an exciton-coupled circular dichroism (CD) technique. Our analytical strategies of CD spectroscopy based on the experimental and theoretical approach effectively clarified the underlying mechanism of Glc and Gal recognition by benzoxaborole dimer 1.

    DOI: 10.1246/cl.200244

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  5. 3,4-Dibromo-7-Azaindole Modulates Arabidopsis Circadian Clock by Inhibiting Casein Kinase 1 Activity 査読有り

    Ono Azusa, Sato Ayato, Fujimoto Kazuhiro J., Matsuo Hiromi, Yanai Takeshi, Kinoshita Toshinori, Nakamichi Norihito

    PLANT AND CELL PHYSIOLOGY   60 巻 ( 11 ) 頁: 2360 - 2368   2019年11月

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    記述言語:英語   出版者・発行元:Plant and Cell Physiology  

    The circadian clock is a timekeeping system for regulation of numerous biological daily rhythms. One characteristic of the circadian clock is that period length remains relatively constant in spite of environmental fluctuations, such as temperature change. Here, using the curated collection of in-house small molecule chemical library (ITbM chemical library), we show that small molecule 3,4-dibromo-7-azaindole (B-AZ) lengthened the circadian period of Arabidopsis thaliana (Arabidopsis). B-AZ has not previously been reported to have any biological and biochemical activities. Target identification can elucidate the mode of action of small molecules, but we were unable to make a molecular probe of B-AZ for target identification. Instead, we performed other analysis, gene expression profiling that potentially reveals mode of action of molecules. Short-term treatment of B-AZ decreased the expression of four dawn- and morning-phased clock-associated genes, CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1), LATE ELONGATED HYPOCOTYL (LHY), PSEUDO-RESPONSE REGULATOR 9 (PRR9) and PRR7. Consistently, amounts of PRR5 and TIMING OF CAB EXPRESSION 1 (TOC1) proteins, transcriptional repressors of CCA1, LHY, PRR9 and PRR7 were increased upon B-AZ treatment. B-AZ inhibited Casein Kinase 1 family (CK1) that phosphorylates PRR5 and TOC1 for targeted degradation. A docking study and molecular dynamics simulation suggested that B-AZ interacts with the ATP-binding pocket of human CK1 delta, whose amino acid sequences are highly similar to those of Arabidopsis CK1. B-AZ-induced period-lengthening effect was attenuated in prr5 toc1 mutants. Collectively, this study provides a novel and simple structure CK1 inhibitor that modulates circadian clock via accumulation of PRR5 and TOC1.

    DOI: 10.1093/pcp/pcz183

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MISC 1

  1. 高精度電子カップリング計算で迫る生体分子系の光学特性

    藤本和宏  

    化学と工業74 巻   頁: 585 - 587   2021年8月

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    記述言語:日本語