1
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Fujisawa T, Unno M. Near-Infrared Excited Raman Optical Activity as a Tool to Uncover Active Sites of Photoreceptor Proteins. J Phys Chem B 2024; 128:2228-2235. [PMID: 38441478 DOI: 10.1021/acs.jpcb.4c00094] [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: 03/16/2024]
Abstract
Raman optical activity (ROA) is a chiral sensitive technique to measure the difference in Raman scattering intensity between right and left circularly polarized light. The method has been applied to the study of biological molecules such as proteins, and it is now recognized as a powerful tool for investigating biomolecular structures. We have expanded the capability of this chiroptical technique to colored molecules, such as photoreceptor proteins, by using a near-infrared excitation. A photoreceptor protein contains a light-absorbing chromophore as an active site, and the precise determination of its structure is vital for comprehending the protein's function at the atomic level. In a photoreceptor protein, the protein environment can distort an achiral chromophore into a chiral conformation. ROA spectroscopy offers detailed structural information about the chromophore under physiological conditions. Here we explore recent progress in near-infrared ROA spectroscopy and its application to biological systems.
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Affiliation(s)
- Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
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2
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Fujisawa T, Shingae T, Ren J, Haraguchi S, Hanamoto T, Hoff WD, Unno M. Spectroscopic Validation of Crystallographic Structures of a Protein Active Site by Chiroptical Spectroscopy. J Phys Chem Lett 2023; 14:9304-9309. [PMID: 37816034 DOI: 10.1021/acs.jpclett.3c01954] [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: 10/12/2023]
Abstract
Out-of-plane distortions of a cofactor molecule in a protein active site are functionally important, and in photoreceptors, it has been proposed that they are crucial for spectral tuning and energy storage in photocycle intermediates. However, these subtle structural features are often beyond the grasp of structural biology. This issue is strikingly exemplified by photoactive yellow protein: its 14 independently determined crystal structures exhibit considerable differences in the dihedral angles defining the chromophore geometry, even though most of these are at excellent resolution. Here we developed a strategy to verify cofactor distortions in crystal structures by using quantum chemical calculations and chiroptical spectroscopy, particularly Raman optical activity and electronic circular dichroism spectroscopies. Based on this approach, we identify seven crystal structures with the chromophore geometries inconsistent with the experimentally observed data. The strategy implemented here promises to be widely applicable to uncovering cofactor distortions at active sites and to studies of reaction intermediates.
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Affiliation(s)
- Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Takahito Shingae
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Jie Ren
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Shojiro Haraguchi
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Takeshi Hanamoto
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Wouter D Hoff
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
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3
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Nishikawa K, Kuroiwa R, Tamogami J, Unno M, Fujisawa T. Raman Optical Activity of Retinal Chromophore in Sensory Rhodopsin II. J Phys Chem B 2023; 127:7244-7250. [PMID: 37556781 DOI: 10.1021/acs.jpcb.3c02391] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/11/2023]
Abstract
Raman optical activity (ROA) spectroscopy was used to study the conformation of the retinal chromophore in sensory rhodopsin II (SRII), which is a blue-green light sensor of microbes. The ROA spectrum consisted of the negative vibrational bands of the chromophore, whose relative intensities are similar to those of the parent Raman spectrum. This spectral feature was explained by the left-handed helical twist of the retinal chromophore on the basis of quantum chemical calculations. On the other hand, we found that the chromophore conformation based on the crystal structures of SRII has a right-handed helical twist, which does not agree with the observation. This specific result suggests that the consistency with chiro-optical properties can be a key criterion for the accurate prediction and/or evaluation of chromophore conformation in retinal-binding proteins.
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Affiliation(s)
- Kouhei Nishikawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Ryosuke Kuroiwa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Jun Tamogami
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
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4
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Ohya M, Kikukawa T, Matsuo J, Tsukamoto T, Nagaura R, Fujisawa T, Unno M. Structure and Heterogeneity of Retinal Chromophore in Chloride Pump Rhodopsins Revealed by Raman Optical Activity. J Phys Chem B 2023. [PMID: 37201188 DOI: 10.1021/acs.jpcb.3c01801] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Chloride transport by microbial rhodopsins is actively being researched to understand how light energy is converted to drive ion pumping across cell membranes. Chloride pumps have been identified in archaea and eubacteria, and there are similarities and differences in the active site structures between these groups. Thus, it has not been clarified whether a common mechanism underlies the ion pump processes for all chloride-pumping rhodopsins. Here, we applied Raman optical activity (ROA) spectroscopy to two chloride pumps, Nonlabens marinus rhodopsin-3 (NM-R3) and halorhodopsin from the cyanobacterium Mastigocladopsis repens (MrHR). ROA is a vibrational spectroscopy that provides chiral sensitivity, and the sign of ROA signals can reveal twisting of cofactor molecules within proteins. Our ROA analysis revealed that the retinal Schiff base NH group orients toward the C helix and forms a direct hydrogen bond with a nearby chloride ion in NM-R3. In contrast, MrHR is suggested to contain two retinal conformations twisted in opposite directions; one conformation has a hydrogen bond with a chloride ion like NM-R3, while the other forms a hydrogen bond with a water molecule anchored by a G helix residue. These results suggest a general pump mechanism in which the chloride ion is "dragged" by the flipping Schiff base NH group upon photoisomerization.
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Affiliation(s)
- Masaiku Ohya
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Takashi Kikukawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Junpei Matsuo
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Takashi Tsukamoto
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Ryota Nagaura
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
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5
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Pu R, Wang Z, Zhu R, Jiang J, Weng TC, Huang Y, Liu W. Investigation of Ultrafast Configurational Photoisomerization of Bilirubin Using Femtosecond Stimulated Raman Spectroscopy. J Phys Chem Lett 2023; 14:809-816. [PMID: 36655842 DOI: 10.1021/acs.jpclett.2c03535] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Phototherapy is an efficient and safe way to reduce high levels of free 4Z,15Z-bilirubin (ZZ-BR) in the serum of newborns. The success of BR phototherapy lies in photoinduced configurational and structural isomerization processes that form excretable isomers. However, the physical picture of photoinduced photoisomerization of ZZ-BR is still unclear. Here, we strategically implement tunable femtosecond stimulated Raman spectroscopy and several time-resolved electronic spectroscopies, assisted by quantum chemical calculations, to dissect the detailed primary configurational isomerization dynamics of free ZZ-BR in organic solvents. The results of this study demonstrate that upon photoexcitation, ultrafast configurational isomerization proceeds by a volume-conserving "hula twist", followed by intramolecular hydrogen-bond distortion and large-scale rotation of the two dipyrrinone halves of the ZZ-BR isomer in a few picoseconds. After that, most of the population recovers back to ZZ-BR, and a very small amount is converted into stable BR isomers via structural isomerization.
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Affiliation(s)
- Ruihua Pu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- STU and SIOM Joint Laboratory for Superintense Lasers and the Applications, Shanghai 201210, China
| | - Ziyu Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- STU and SIOM Joint Laboratory for Superintense Lasers and the Applications, Shanghai 201210, China
| | - Ruixue Zhu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Jiaming Jiang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Tsu-Chien Weng
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yifan Huang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Weimin Liu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- STU and SIOM Joint Laboratory for Superintense Lasers and the Applications, Shanghai 201210, China
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6
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Fujisawa T, Kinoue K, Seike R, Kikukawa T, Unno M. Reisomerization of retinal represents a molecular switch mediating Na + uptake and release by a bacterial sodium-pumping rhodopsin. J Biol Chem 2022; 298:102366. [PMID: 35963435 PMCID: PMC9483557 DOI: 10.1016/j.jbc.2022.102366] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 08/08/2022] [Accepted: 08/09/2022] [Indexed: 11/27/2022] Open
Abstract
Sodium-pumping rhodopsins (NaRs) are membrane transporters that utilize light energy to pump Na+ across the cellular membrane. Within the NaRs, the retinal Schiff base chromophore absorbs light, and a photochemically induced transient state, referred to as the “O intermediate”, performs both the uptake and release of Na+. However, the structure of the O intermediate remains unclear. Here, we used time-resolved cryo-Raman spectroscopy under preresonance conditions to study the structure of the retinal chromophore in the O intermediate of an NaR from the bacterium Indibacter alkaliphilus. We observed two O intermediates, termed O1 and O2, having distinct chromophore structures. We show O1 displays a distorted 13-cis chromophore, while O2 contains a distorted all-trans structure. This finding indicated that the uptake and release of Na+ are achieved not by a single O intermediate but by two sequential O intermediates that are toggled via isomerization of the retinal chromophore. These results provide crucial structural insight into the unidirectional Na+ transport mediated by the chromophore-binding pocket of NaRs.
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Affiliation(s)
- Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan.
| | - Kouta Kinoue
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Ryouhei Seike
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Takashi Kikukawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan; Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sappo-ro 060-0810, Japan
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan.
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7
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Fujisawa T, Nishikawa K, Tamogami J, Unno M. Conformational Analysis of a Retinal Schiff Base Chromophore in Proteorhodopsin by Raman Optical Activity. J Phys Chem Lett 2021; 12:9564-9568. [PMID: 34581580 DOI: 10.1021/acs.jpclett.1c02552] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Raman optical activity (ROA) spectroscopy was used to study the conformation of the retinal Schiff base chromophore in green-light-absorbing proteorhodopsin, which is a globally distributed light-driven proton pump of aquatic bacteria. The ROA spectrum consisted mostly of the negative vibrational bands of the chromophore, while the hydrogen out-of-plane mode (at 960 cm-1) appeared as the sole positive band. This distinct spectral feature was not explained by the twisted structure of the retinal Schiff base but was reproduced by the structural model in which the polyene chain on the β-ionone ring side was bent out-of-plane. The bent chromophore structure potentially couples with proton pumping through the motion of the sixth helix in contact with the β-ionone ring.
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Affiliation(s)
- Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Kouhei Nishikawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Jun Tamogami
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
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8
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Machalska E, Zajac G, Wierzba AJ, Kapitán J, Andruniów T, Spiegel M, Gryko D, Bouř P, Baranska M. Recognition of the True and False Resonance Raman Optical Activity. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202107600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ewa Machalska
- Faculty of Chemistry Jagiellonian University Gronostajowa 2 30-387 Krakow Poland
- Jagiellonian Centre for Experimental Therapeutics (JCET) Jagiellonian University Bobrzynskiego 14 30-348 Krakow Poland
| | - Grzegorz Zajac
- Jagiellonian Centre for Experimental Therapeutics (JCET) Jagiellonian University Bobrzynskiego 14 30-348 Krakow Poland
- Institute of Organic Chemistry and Biochemistry Academy of Sciences Flemingovo náměstí 2 16610 Prague Czech Republic
| | - Aleksandra J. Wierzba
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
| | - Josef Kapitán
- Department of Optics Palacký University Olomouc 17. listopadu 12 77146 Olomouc Czech Republic
| | - Tadeusz Andruniów
- Department of Chemistry Wroclaw University of Science and Technology Wyb. Wyspianskiego 27 50-370 Wroclaw Poland
| | - Maciej Spiegel
- Department of Pharmacognosy and Herbal Medicine Wroclaw Medical University Borowska 211A 50-556 Wroclaw Poland
| | - Dorota Gryko
- Institute of Organic Chemistry Polish Academy of Sciences Kasprzaka 44/52 01-224 Warsaw Poland
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry Academy of Sciences Flemingovo náměstí 2 16610 Prague Czech Republic
| | - Malgorzata Baranska
- Faculty of Chemistry Jagiellonian University Gronostajowa 2 30-387 Krakow Poland
- Jagiellonian Centre for Experimental Therapeutics (JCET) Jagiellonian University Bobrzynskiego 14 30-348 Krakow Poland
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9
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Machalska E, Zajac G, Wierzba AJ, Kapitán J, Andruniów T, Spiegel M, Gryko D, Bouř P, Baranska M. Recognition of the True and False Resonance Raman Optical Activity. Angew Chem Int Ed Engl 2021; 60:21205-21210. [PMID: 34216087 PMCID: PMC8519086 DOI: 10.1002/anie.202107600] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/01/2021] [Indexed: 12/16/2022]
Abstract
Resonance Raman optical activity (RROA) possesses all aspects of a sensitive tool for molecular detection, but its measurement remains challenging. We demonstrate that reliable recording of RROA of chiral colorful compounds is possible, but only after considering the effect of the electronic circular dichroism (ECD) on the ROA spectra induced by the dissolved chiral compound. We show RROA for a number of model vitamin B12 derivatives that are chemically similar but exhibit distinctively different spectroscopic behavior. The ECD/ROA effect is proportional to the concentration and dependent on the optical pathlength of the light propagating through the sample. It can severely alter relative band intensities and signs in the natural RROA spectra. The spectra analyses are supported by computational modeling based on density functional theory. Neglecting the ECD effect during ROA measurement can lead to misinterpretation of the recorded spectra and erroneous conclusions about the molecular structure.
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Affiliation(s)
- Ewa Machalska
- Faculty of ChemistryJagiellonian UniversityGronostajowa 230-387KrakowPoland
- Jagiellonian Centre for Experimental Therapeutics (JCET)Jagiellonian UniversityBobrzynskiego 1430-348KrakowPoland
| | - Grzegorz Zajac
- Jagiellonian Centre for Experimental Therapeutics (JCET)Jagiellonian UniversityBobrzynskiego 1430-348KrakowPoland
- Institute of Organic Chemistry and BiochemistryAcademy of SciencesFlemingovo náměstí 216610PragueCzech Republic
| | - Aleksandra J. Wierzba
- Institute of Organic ChemistryPolish Academy of SciencesKasprzaka 44/5201-224WarsawPoland
| | - Josef Kapitán
- Department of OpticsPalacký University Olomouc17. listopadu 1277146OlomoucCzech Republic
| | - Tadeusz Andruniów
- Department of ChemistryWroclaw University of Science and TechnologyWyb. Wyspianskiego 2750-370WroclawPoland
| | - Maciej Spiegel
- Department of Pharmacognosy and Herbal MedicineWroclaw Medical UniversityBorowska 211A50-556WroclawPoland
| | - Dorota Gryko
- Institute of Organic ChemistryPolish Academy of SciencesKasprzaka 44/5201-224WarsawPoland
| | - Petr Bouř
- Institute of Organic Chemistry and BiochemistryAcademy of SciencesFlemingovo náměstí 216610PragueCzech Republic
| | - Malgorzata Baranska
- Faculty of ChemistryJagiellonian UniversityGronostajowa 230-387KrakowPoland
- Jagiellonian Centre for Experimental Therapeutics (JCET)Jagiellonian UniversityBobrzynskiego 1430-348KrakowPoland
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10
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All-dielectric chiral-field-enhanced Raman optical activity. Nat Commun 2021; 12:3062. [PMID: 34031409 PMCID: PMC8144208 DOI: 10.1038/s41467-021-23364-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 04/20/2021] [Indexed: 11/10/2022] Open
Abstract
Raman optical activity (ROA) is effective for studying the conformational structure and behavior of chiral molecules in aqueous solutions and is advantageous over X-ray crystallography and nuclear magnetic resonance spectroscopy in sample preparation and cost performance. However, ROA signals are inherently minuscule; 3–5 orders of magnitude weaker than spontaneous Raman scattering due to the weak chiral light–matter interaction. Localized surface plasmon resonance on metallic nanoparticles has been employed to enhance ROA signals, but suffers from detrimental spectral artifacts due to its photothermal heat generation and inability to efficiently transfer and enhance optical chirality from the far field to the near field. Here we demonstrate all-dielectric chiral-field-enhanced ROA by devising a silicon nanodisk array and exploiting its dark mode to overcome these limitations. Specifically, we use it with pairs of chemical and biological enantiomers to show >100x enhanced chiral light–molecule interaction with negligible artifacts for ROA measurements. Raman optical activity (ROA) is useful for studying conformational structure and behavior of chiral molecules, but is limited by the weak signals. Here, the authors demonstrate 100x signal enhancement via an all-dielectric approach, using a silicon nanodisk array and exploiting its dark mode.
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11
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Unno M, Hirose Y, Mishima M, Kikukawa T, Fujisawa T, Iwata T, Tamogami J. Spectroscopic approach for exploring structure and function of photoreceptor proteins. Biophys Physicobiol 2021; 18:127-130. [PMID: 34178563 PMCID: PMC8214923 DOI: 10.2142/biophysico.bppb-v18.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 05/11/2021] [Indexed: 12/01/2022] Open
Affiliation(s)
- Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Yuu Hirose
- Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan
| | - Masaki Mishima
- Department of Molecular Biophysics, Tokyo University of Pharmacy and Life Sciences, School of Pharmacy, Hachioji, Tokyo 192-0392, Japan
| | - Takashi Kikukawa
- Faculty of Advanced Life Science and Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Tatsuya Iwata
- Department of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, Japan
| | - Jun Tamogami
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan
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12
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Nakamizo Y, Fujisawa T, Kikukawa T, Okamura A, Baba H, Unno M. Low-temperature Raman spectroscopy of sodium-pump rhodopsin from Indibacter alkaliphilus: insight of Na + binding for active Na + transport. Phys Chem Chem Phys 2021; 23:2072-2079. [PMID: 33433533 DOI: 10.1039/d0cp05652a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We carried out the low-temperature Raman measurement of a sodium pump rhodopsin from Indibacter alkaliphilus (IaNaR) and examined the primary structural change for the light-driven Na+ pump. We observed that photoexcitation of IaNaR produced the distorted 13-cis retinal chromophore in the presence of Na+, while the structural distortion was significantly relaxed in the absence of Na+. This structural difference of the chromophore with/without Na+ was attributed to the Na+ binding to the protein, which alters the active site. Using the spectral sensitivity to the ion binding, we found that IaNaR had a second Na+ binding site in addition to the one already specified on the extracellular surface. To date, the Na+ binding has not been considered as a prerequisite for Na+ transport. However, this study provides insight that the protein structural change induced by the ion binding involved the formation of an R108-D250 salt bridge, which has critical importance in the active transport of Na+.
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Affiliation(s)
- Yushi Nakamizo
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan.
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13
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Kamura S, Tani T, Matsuo H, Onaka Y, Fujisawa T, Unno M. New Probe for Porcelain Glazes by Luminescence at Near-Infrared Excitation. ACS OMEGA 2021; 6:7829-7833. [PMID: 33778294 PMCID: PMC7992157 DOI: 10.1021/acsomega.1c00322] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 03/02/2021] [Indexed: 05/06/2023]
Abstract
Raman spectroscopy is a powerful technique for a wide range of materials, including porcelain, and near-infrared excitation is often used to suppress a fluorescence background from a sample. When we measured the Raman spectra of porcelains at 785 nm excitation, we observed a strong broad band in a high-frequency region, and its origin was not clearly elucidated. In this study, we have measured the spectra of glazed porcelains at 532, 785, and 1064 nm excitation and demonstrated that the broad feature originates from luminescence around 880 nm and not from Raman scattering. We provide experimental evidence showing that the band originates from a thin layer of glaze. Since the band shape depends on the processing temperature, the luminescence spectra can be a nondestructive probe for studying the glass formation of a glaze.
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Affiliation(s)
- Shoutaro Kamura
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Takumi Tani
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Hideyuki Matsuo
- Saga
Ceramics Research Laboratory, 3037-7 Hei Kuromuta, Arita-cho, Nishimatsuura-gun, Saga 844-0022, Japan
| | - Yoshimitsu Onaka
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Tomotsumi Fujisawa
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Masashi Unno
- Department
of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
- Ceramic
Research Center of Saga University, 2441-1 Oono-otsu, Arita-cho, Nishimatsuura-gun, Saga 844-0013, Japan
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14
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Matsuo J, Kikukawa T, Fujisawa T, Hoff WD, Unno M. "Watching" a Molecular Twist in a Protein by Raman Optical Activity. J Phys Chem Lett 2020; 11:8579-8584. [PMID: 32945678 DOI: 10.1021/acs.jpclett.0c02448] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Light-absorbing chromophores in photoreceptors contain a π-electron system and are intrinsically planar molecules. However, within a protein environment these cofactors often become nonplanar and chiral in a manner that is widely believed to be functionally important. When the same chromophore is out-of-plane distorted in opposite directions in different members of a protein family, such conformers become a set of enantiomers. In techniques using chiral optical spectroscopy such as Raman optical activity (ROA), such proteins are expected to show opposite signs in their spectra. Here we use two microbial rhodopsins, Gloeobacter rhodopsin and sodium ion pump rhodopsin (NaR), to provide the first experimental and theoretical evidence that the twist direction of the retinal chromophore indeed determines the sign of the ROA spectrum. We disrupt the hydrogen bond responsible for the distortion of the retinal in NaR and show that the sign of the ROA signals of this nonfunctional mutant is flipped. The reported ROA spectra are monosignate, a property that has been seen for a variety of photoreceptors, which we attribute to an energetically favorable gradual curvature of the chromophore.
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Affiliation(s)
- Junpei Matsuo
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Takashi Kikukawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan
- Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 060-0810, Japan
| | - Tomotsumi Fujisawa
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Wouter D Hoff
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
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Krupová M, Kapitán J, Bouř P. Induced Lanthanide Circularly Polarized Luminescence as a Probe of Protein Fibrils. ACS OMEGA 2019; 4:1265-1271. [PMID: 31459399 PMCID: PMC6648570 DOI: 10.1021/acsomega.8b03175] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 12/27/2018] [Indexed: 06/10/2023]
Abstract
Protein fibrils are involved in a number of biological processes. Because their structure is very complex and not completely understood, different spectroscopic methods are used to monitor different aspects of fibril structure. We have explored circularly polarized luminescence (CPL) induced in lanthanide compounds to indicate fibril growth and discriminate among fibril types. For hen egg-white lysozyme and polyglutamic acid-specific CPL, spectral patterns were obtained and could be correlated with vibrational circular dichroism (VCD) spectra and thioflavin T fluorescence. The CPL spectra were measured on a Raman optical activity spectrometer, and its various polarization modes are discussed. The experiments indicate that the induced CPL is sensitive to more local aspects of the fibril structure than VCD. For CPL, smaller amounts of the sample are required for the analysis, and thus this method appears to be a good candidate for future spectroscopic characterization of these peptide and protein aggregates.
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Affiliation(s)
- Monika Krupová
- Institute
of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí
2, 16610 Prague, Czech Republic
- Faculty
of Mathematics and Physics, Charles University, Ke Karlovu 3, 12116 Prague 2, Czech Republic
| | - Josef Kapitán
- Department
of Optics, Palacký University, 17. listopadu 12, 77146 Olomouc, Czech Republic
| | - Petr Bouř
- Institute
of Organic Chemistry and Biochemistry, Academy of Sciences, Flemingovo náměstí
2, 16610 Prague, Czech Republic
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