1
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Singh M, Hashimoto M, Katayama K, Furutani Y, Kandori H. Internal Proton Transfer in the Activation of Heliorhodopsin. J Mol Biol 2024; 436:168273. [PMID: 37709010 DOI: 10.1016/j.jmb.2023.168273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 09/07/2023] [Accepted: 09/07/2023] [Indexed: 09/16/2023]
Abstract
Heliorhodopsin (HeR), a recently discovered new rhodopsin family, contains a single counterion of the protonated Schiff base, E108 in HeR from Thermoplasmatales archaeon SG8-52-1 (TaHeR). Upon light absorption, the M and O intermediates form in HeRs, as well as type-1 microbial rhodopsins, indicating that the proton transfer from the Schiff base leads to the activation of HeRs. The present flash photolysis study of TaHeR in the presence of a pH-sensitive dye showed that TaHeR contains a proton-accepting group (PAG) inside protein. Comprehensive mutation study of TaHeR found the E108D mutant abolishing the M formation, which is not only at pH 8, but also at pH 9 and 10. The lack of M observation does not originate from the short lifetime of the M intermediate in E108D, as FTIR spectroscopy revealed that a red-shifted K-like intermediate is long lived in E108D. It is likely that the K-like intermediate returns to the unphotolyzed state without internal proton transfer in E108D. E108 and D108 are the Schiff base counterions of the wild-type and E108D mutant TaHeR, respectively, whereas small difference in length of side chains determine internal proton transfer reaction from the Schiff base. Based on the present finding, we propose that the internal water cluster (four water molecules) constitutes PAG in the M intermediate of TaHeR. In the wild type TaHeR, a protonated water cluster is stabilized by forming a salt bridge with E108. In contrast, slightly shortened counterion (D108) cannot stabilize the protonated water cluster in E108D, and thus impairs internal proton transfer from the Schiff base.
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Affiliation(s)
- Manish Singh
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Masanori Hashimoto
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Kota Katayama
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan; OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan; PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Yuji Furutani
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan; OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan; OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
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2
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Urui T, Hayashi K, Mizuno M, Inoue K, Kandori H, Mizutani Y. Cis- Trans Reisomerization Preceding Reprotonation of the Retinal Chromophore Is Common to the Schizorhodopsin Family: A Simple and Rational Mechanism for Inward Proton Pumping. J Phys Chem B 2024; 128:744-754. [PMID: 38204413 DOI: 10.1021/acs.jpcb.3c07510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2024]
Abstract
The creation of unidirectional ion transporters across membranes represents one of the greatest challenges in chemistry. Proton-pumping rhodopsins are composed of seven transmembrane helices with a retinal chromophore bound to a lysine side chain via a Schiff base linkage and provide valuable insights for designing such transporters. What makes these transporters particularly intriguing is the discovery of both outward and inward proton-pumping rhodopsins. Surprisingly, despite sharing identical overall structures and membrane topologies, these proteins facilitate proton transport in opposite directions, implying an underlying rational mechanism that can transport protons in different directions within similar protein structures. In this study, we unraveled this mechanism by examining the chromophore structures of deprotonated intermediates in schizorhodopsins, a recently discovered subfamily of inward proton-pumping rhodopsins, using time-resolved resonance Raman spectroscopy. The photocycle of schizorhodopsins revealed the cis-trans thermal isomerization that precedes reprotonation at the Schiff base of the retinal chromophore. Notably, this order has not been observed in other proton-pumping rhodopsins, but here, it was observed in all seven schizorhodopsins studied across the archaeal domain, strongly suggesting that cis-trans thermal isomerization preceding reprotonation is a universal feature of the schizorhodopsin family. Based on these findings, we propose a structural basis for the remarkable order of events crucial for facilitating inward proton transport. The mechanism underlying inward proton transport by schizorhodopsins is straightforward and rational. The insights obtained from this study hold great promise for the design of transmembrane unidirectional ion transporters.
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Affiliation(s)
- Taito Urui
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Kouhei Hayashi
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Keiichi Inoue
- The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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3
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Li Z, Mizuno M, Ejiri T, Hayashi S, Kandori H, Mizutani Y. Unique Vibrational Characteristics and Structures of the Photoexcited Retinal Chromophore in Ion-Pumping Rhodopsins. J Phys Chem B 2023; 127:9873-9886. [PMID: 37940604 DOI: 10.1021/acs.jpcb.3c02146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Photoisomerization of an all-trans-retinal chromophore triggers ion transport in microbial ion-pumping rhodopsins. Understanding chromophore structures in the electronically excited (S1) state provides insights into the structural evolution on the potential energy surface of the photoexcited state. In this study, we examined the structure of the S1-state chromophore in Natronomonas pharaonis halorhodopsin (NpHR), a chloride ion-pumping rhodopsin, using time-resolved resonance Raman spectroscopy. The spectral patterns of the S1-state chromophore were completely different from those of the ground-state chromophore, resulting from unique vibrational characteristics and the structure of the S1 state. Mode assignments were based on a combination of deuteration shifts of the Raman bands and hybrid quantum mechanics-molecular mechanics calculations. The present observations suggest a weakened bond alternation in the π conjugation system. A strong hydrogen-out-of-plane bending band was observed in the Raman spectra of the S1-state chromophore in NpHR, indicating a twisted polyene structure. Similar frequency shifts for the C═N/C═C and C-C stretching modes of the S1-state chromophore in NpHR were observed in the Raman spectra of sodium ion-pumping and proton-pumping rhodopsins, suggesting that these unique features are common to the S1 states of ion-pumping rhodopsins.
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Affiliation(s)
- Zixuan Li
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Osaka, Toyonaka 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Osaka, Toyonaka 560-0043, Japan
| | - Tomo Ejiri
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Shigehiko Hayashi
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Osaka, Toyonaka 560-0043, Japan
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4
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Chiba Y, Tsujimura M, Saito K, Ishikita H. pH-Dependent Binding and Releasing Mechanism of Acetate in the Inner Water Cavity of Heliorhodopsin. Biochemistry 2023; 62:2363-2370. [PMID: 37471424 PMCID: PMC10434121 DOI: 10.1021/acs.biochem.3c00193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 06/28/2023] [Indexed: 07/22/2023]
Abstract
The high-resolution structure of heliorhodopsin crystallized at low pH reveals the presence of a planar triangle molecule, acetate, in the inner water cavity. Here, we investigate how the acetate molecule is stabilized at the counterion Glu107 moiety, using molecular dynamics (MD) simulations and a quantum mechanical/molecular mechanical (QM/MM) approach. QM/MM calculations indicate that the density is best described as acetate among triangle acids, including nitric acid and bicarbonate. The calculated protonation state indicates that protonated acetate donates an H-bond to deprotonated Glu107 in the low-pH crystal structure. The observed red-shift of ∼30 nm in the absorption wavelength with pKa ≈ 4 is likely due to the His23/His80 protonation, rather than the Glu107 protonation. MD simulations also show that acetate can exist at the Glu107 moiety only when it is protonated. When ionized, acetate is released from the Glu107 moiety via Asn101 at the channel bottleneck and Arg91 on the intracellular protein surface. These observations could explain how acetate binds at low pH and releases at high pH.
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Affiliation(s)
- Yoshihiro Chiba
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Masaki Tsujimura
- Department
of Advanced Interdisciplinary Studies, The
University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Keisuke Saito
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research
Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Hiroshi Ishikita
- Department
of Applied Chemistry, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
- Research
Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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5
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Ganapathy S, Meng X, Mossel D, Jagt M, Brinks D. Expanding the family of genetically encoded voltage indicators with a candidate Heliorhodopsin exhibiting near-infrared fluorescence. J Biol Chem 2023; 299:104771. [PMID: 37127067 DOI: 10.1016/j.jbc.2023.104771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 04/22/2023] [Accepted: 04/23/2023] [Indexed: 05/03/2023] Open
Abstract
Genetically encoded voltage indicators (GEVIs), particularly those based on microbial rhodopsins, are gaining traction in neuroscience as fluorescent sensors for imaging voltage dynamics with high-spatiotemporal precision. Here we establish a novel GEVI candidate based on the recently discovered subfamily of the microbial rhodopsin clade, termed heliorhodopsins. We discovered that upon excitation at 530-560nm, wild type heliorhodopsin exhibits near infra-red fluorescence which is sensitive to membrane voltage. We characterized the fluorescence brightness, photostability, voltage sensitivity and kinetics of wild type heliorhodopsin in HEK293T cells and further examined the impact of mutating key residues near the retinal chromophore. The S237A mutation significantly improved the fluorescence response of heliorhodopsin by 76% providing a highly promising starting point for further protein evolution.
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Affiliation(s)
- Srividya Ganapathy
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands; Department of Pediatrics & Cellular and Molecular Medicine, UCSD School of Medicine, San Diego, USA
| | - Xin Meng
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | - Delizzia Mossel
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | - Mels Jagt
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands
| | - Daan Brinks
- Department of Imaging Physics, Delft University of Technology, Delft, The Netherlands; Department of Molecular Genetics, Erasmus University Medical Center, Rotterdam, The Netherlands.
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6
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Tsujimura M, Chiba Y, Saito K, Ishikita H. Proton transfer and conformational changes along the hydrogen bond network in heliorhodopsin. Commun Biol 2022; 5:1336. [PMID: 36474019 PMCID: PMC9726877 DOI: 10.1038/s42003-022-04311-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 11/28/2022] [Indexed: 12/12/2022] Open
Abstract
Heliorhodopsin releases a proton from the Schiff base during the L-state to M-state transition but not toward the protein bulk surface. Here we investigate proton transfer and induced structural changes along the H-bond network in heliorhodopsin using a quantum mechanical/molecular mechanical approach and molecular dynamics simulations. Light-induced proton transfer could occur from the Schiff base toward Glu107, reorienting Ser76, followed by subsequent proton transfer toward His80. His80 protonation induces the reorientation of Trp246 on the extracellular surface, originating from the electrostatic interaction that propagates along the transmembrane H-bond network [His80…His23…H2O[H23/Q26]…Gln26…Trp246] over a distance of 15 Å. Furthermore, it induces structural fluctuation on the intracellular side in the H-bond network [His80…Asn16…Tyr92…Glu230…Arg104…Glu149], opening the inner cavity at the Tyr92 moiety. These may be a basis of how light-induced proton transfer causes conformational changes during the M-state to O-state transition.
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Affiliation(s)
- Masaki Tsujimura
- grid.26999.3d0000 0001 2151 536XDepartment of Advanced Interdisciplinary Studies, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 Japan
| | - Yoshihiro Chiba
- grid.26999.3d0000 0001 2151 536XDepartment of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654 Japan
| | - Keisuke Saito
- grid.26999.3d0000 0001 2151 536XDepartment of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654 Japan ,grid.26999.3d0000 0001 2151 536XResearch Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 Japan
| | - Hiroshi Ishikita
- grid.26999.3d0000 0001 2151 536XDepartment of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654 Japan ,grid.26999.3d0000 0001 2151 536XResearch Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 Japan
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7
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Urui T, Das I, Mizuno M, Sheves M, Mizutani Y. Origin of a Double-Band Feature in the Ethylenic C═C Stretching Modes of the Retinal Chromophore in Heliorhodopsins. J Phys Chem B 2022; 126:8680-8688. [PMID: 36281583 DOI: 10.1021/acs.jpcb.2c04883] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Photoreceptor proteins play a critical role in light utilization for energy conversion and environmental sensing. Rhodopsin is a prototypical photoreceptor protein containing a retinal group that functions as a light-receptive site. It is essential to characterize the structure of the retinal chromophore because the chromophore structure, along with retinal-protein interactions, regulates which wavelengths of light are absorbed. Resonance Raman spectroscopy is a powerful tool to characterize chromophore structures in proteins. The resonance Raman spectra of heliorhodopsins, a recently discovered rhodopsin family, were previously reported to exhibit two intense ethylenic C═C stretching bands never observed for type-1 rhodopsins. Here, we show that the double-band feature in the ethylenic C═C stretching modes is not due to structural inhomogeneity but rather to the retinal polyene chain's linear structure. It contrasts with bent all-trans chromophore in type-1 rhodopsins. The linear structure of the chromophore results from weak atomic contacts between the 13-methyl group and a nearby Trp side chain, which can slow thermal reisomerization in the photocycle. It is possible that the deceleration of reisomerization increases the lifetime of the signaling intermediate for photosensory function.
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Affiliation(s)
- Taito Urui
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka 560-0043, Osaka, Japan
| | - Ishita Das
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76305, Israel
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka 560-0043, Osaka, Japan
| | - Mordechai Sheves
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76305, Israel
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka 560-0043, Osaka, Japan
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8
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Hayashi K, Mizuno M, Kandori H, Mizutani Y. Cis-Trans Reisomerization Precedes Reprotonation of the Retinal Chromophore in the Photocycle of Schizorhodopsin 4. Angew Chem Int Ed Engl 2022; 61:e202203149. [PMID: 35749139 DOI: 10.1002/anie.202203149] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Indexed: 11/08/2022]
Abstract
Recent discoveries of light-driven inward proton-pumping rhodopsins have opened new avenues to exploring the mechanism of unidirectional transport because these proteins transport protons in the opposite direction to conventional proton-pumping rhodopsins, despite their similar protein structure and membrane topology. Schizorhodopsin (SzR) is a newly discovered rhodopsin family of light-driven inward proton pumps. Here, we report time-resolved resonance Raman spectra showing that cis-trans thermal reisomerization precedes reprotonation at the Schiff base of the retinal chromophore in the photocycle of SzR AM_5_00977. This sequence has not been observed for the photocycles of conventional proton-pumping rhodopsins, in which reisomerization follows reprotonation, and thus provides insights into the mechanism of proton uptake to the chromophore during inward proton pumping. The present findings are expected to contribute to controlling the direction of proton transport in engineered proteins.
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Affiliation(s)
- Kouhei Hayashi
- Department of Chemistry, School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan.,Department of Chemistry, School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Aichi, 466-8555, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan.,Department of Chemistry, School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
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9
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Hayashi K, Mizuno M, Kandori H, Mizutani Y. Cis‐Trans Reisomerization Precedes Reprotonation of the Retinal Chromophore in the Photocycle of Schizorhodopsin 4. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202203149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Misao Mizuno
- Osaka University: Osaka Daigaku Graduate School of Science 1-1 MachikaneyamaToyonaka 560-0043 JAPAN
| | - Hideki Kandori
- Nagoya Institute of Technology: Nagoya Kogyo Daigaku Department of Life Science and Applied Chemistry JAPAN
| | - Yasuhisa Mizutani
- Osaka University: Osaka Daigaku Graduate School of Science 1-1 Machikaneyama 560-0043 Toyonaka JAPAN
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