1
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Malakar P, Gholami S, Aarabi M, Rivalta I, Sheves M, Garavelli M, Ruhman S. Retinal photoisomerization versus counterion protonation in light and dark-adapted bacteriorhodopsin and its primary photoproduct. Nat Commun 2024; 15:2136. [PMID: 38459010 PMCID: PMC10923925 DOI: 10.1038/s41467-024-46061-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 02/08/2024] [Indexed: 03/10/2024] Open
Abstract
Discovered over 50 years ago, bacteriorhodopsin is the first recognized and most widely studied microbial retinal protein. Serving as a light-activated proton pump, it represents the archetypal ion-pumping system. Here we compare the photochemical dynamics of bacteriorhodopsin light and dark-adapted forms with that of the first metastable photocycle intermediate known as "K". We observe that following thermal double isomerization of retinal in the dark from bio-active all-trans 15-anti to 13-cis, 15-syn, photochemistry proceeds even faster than the ~0.5 ps decay of the former, exhibiting ballistic wave packet curve crossing to the ground state. In contrast, photoexcitation of K containing a 13-cis, 15-anti chromophore leads to markedly multi-exponential excited state decay including much slower stages. QM/MM calculations, aimed to interpret these results, highlight the crucial role of protonation, showing that the classic quadrupole counterion model poorly reproduces spectral data and dynamics. Single protonation of ASP212 rectifies discrepancies and predicts triple ground state structural heterogeneity aligning with experimental observations. These findings prompt a reevaluation of counter ion protonation in bacteriorhodopsin and contribute to the broader understanding of its photochemical dynamics.
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Affiliation(s)
- Partha Malakar
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Samira Gholami
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy
| | - Mohammad Aarabi
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy
| | - Ivan Rivalta
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy
- ENSL, CNRS, Laboratoire de Chimie UMR 5182, 46 allée d'Italie, 69364, Lyon, France
| | - Mordechai Sheves
- Department of Molecular Chemistry and Materials Science, The Weizmann Institute of Science, Rehovot, 7610001, Israel.
| | - Marco Garavelli
- Dipartimento di Chimica industriale "Toso Montanari", Università di Bologna, Viale del Risorgimento 4, 40136, Bologna, Italy.
| | - Sanford Ruhman
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel.
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2
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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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3
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Chang C, Kuramochi H, Singh M, Abe‐Yoshizumi R, Tsukuda T, Kandori H, Tahara T. A Unified View on Varied Ultrafast Dynamics of the Primary Process in Microbial Rhodopsins. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202111930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Chun‐Fu Chang
- Molecular Spectroscopy Laboratory RIKEN 2-1 Hirosawa Wako Saitama 351-0198 Japan
- Department of Chemistry Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-Ku Tokyo 113-0033 Japan
| | - Hikaru Kuramochi
- Molecular Spectroscopy Laboratory RIKEN 2-1 Hirosawa Wako Saitama 351-0198 Japan
- Ultrafast Spectroscopy Research Team RIKEN Center for Advanced Photonics (RAP), RIKEN 2-1 Hirosawa Wako Saitama 351-0198 Japan
- PRESTO (Japan) Science and Technology Agency 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan
- Present address: Research Center of Integrative Molecular Systems Institute for Molecular Science 38 Nishigo-Naka Myodaiji Okazaki 444-8585 Japan
| | - Manish Singh
- Department of Life Science and Applied Chemistry Nagoya Institute of Technology, Showa-Ku Nagoya Aichi 466-8555 Japan
| | - Rei Abe‐Yoshizumi
- Department of Life Science and Applied Chemistry Nagoya Institute of Technology, Showa-Ku Nagoya Aichi 466-8555 Japan
| | - Tatsuya Tsukuda
- Department of Chemistry Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-Ku Tokyo 113-0033 Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry Nagoya Institute of Technology, Showa-Ku Nagoya Aichi 466-8555 Japan
- OptoBioTechnology Research Center Nagoya Institute of Technology Showa-Ku, Nagoya Aichi 466-8555 Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory RIKEN 2-1 Hirosawa Wako Saitama 351-0198 Japan
- Ultrafast Spectroscopy Research Team RIKEN Center for Advanced Photonics (RAP), RIKEN 2-1 Hirosawa Wako Saitama 351-0198 Japan
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4
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Chang CF, Kuramochi H, Singh M, Abe-Yoshizumi R, Tsukuda T, Kandori H, Tahara T. A Unified View on Varied Ultrafast Dynamics of the Primary Process in Microbial Rhodopsins. Angew Chem Int Ed Engl 2021; 61:e202111930. [PMID: 34670002 DOI: 10.1002/anie.202111930] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Indexed: 11/08/2022]
Abstract
All-trans to 13-cis photoisomerization of the protonated retinal Schiff base (PRSB) chromophore is the primary step that triggers various biological functions of microbial rhodopsins. While this ultrafast primary process has been extensively studied, it has been recognized that the relevant excited-state relaxation dynamics differ significantly from one rhodopsin to another. To elucidate the origin of the complicated ultrafast dynamics of the primary process in microbial rhodopsins, we studied the excited-state dynamics of proteorhodopsin, its D97N mutant, and bacteriorhodopsin by femtosecond time-resolved absorption (TA) spectroscopy in a wide pH range. The TA data showed that their excited-state relaxation dynamics drastically change when pH approaches the pKa of the counterion residue of the PRSB chromophore in the ground state. This result reveals that the varied excited-state relaxation dynamics in different rhodopsins mainly originate from the difference of the ground-state heterogeneity (i.e., protonation/deprotonation of the PRSB counterion).
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Affiliation(s)
- Chun-Fu Chang
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-0033, Japan
| | - Hikaru Kuramochi
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,PRESTO (Japan) Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan.,Present address: Research Center of Integrative Molecular Systems, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, 444-8585, Japan
| | - Manish Singh
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-Ku, Nagoya, Aichi, 466-8555, Japan
| | - Rei Abe-Yoshizumi
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-Ku, Nagoya, Aichi, 466-8555, Japan
| | - Tatsuya Tsukuda
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-0033, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-Ku, Nagoya, Aichi, 466-8555, Japan.,OptoBioTechnology Research Center, Nagoya Institute of Technology, Showa-Ku, Nagoya, Aichi, 466-8555, Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
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5
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Smitienko OA, Feldman TB, Petrovskaya LE, Nekrasova OV, Yakovleva MA, Shelaev IV, Gostev FE, Cherepanov DA, Kolchugina IB, Dolgikh DA, Nadtochenko VA, Kirpichnikov MP, Ostrovsky MA. Comparative Femtosecond Spectroscopy of Primary Photoreactions of Exiguobacterium sibiricum Rhodopsin and Halobacterium salinarum Bacteriorhodopsin. J Phys Chem B 2021; 125:995-1008. [PMID: 33475375 DOI: 10.1021/acs.jpcb.0c07763] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The primary stages of the Exiguobacterium sibiricum rhodopsin (ESR) photocycle were investigated by femtosecond absorption laser spectroscopy in the spectral range of 400-900 nm with a time resolution of 25 fs. The dynamics of the ESR photoreaction were compared with the reactions of bacteriorhodopsin (bR) in purple membranes (bRPM) and in recombinant form (bRrec). The primary intermediates of the ESR photocycle were similar to intermediates I, J, and K in bacteriorhodopsin photoconversion. The CONTIN program was applied to analyze the characteristic times of the observed processes and to clarify the reaction scheme. A similar photoreaction pattern was observed for all studied retinal proteins, including two consecutive dynamic Stokes shift phases lasting ∼0.05 and ∼0.15 ps. The excited state decays through a femtosecond reactive pathway, leading to retinal isomerization and formation of product J, and a picosecond nonreactive pathway that leads only to the initial state. Retinal photoisomerization in ESR takes 0.69 ps, compared with 0.48 ps in bRPM and 0.74 ps in bRrec. The nonreactive excited state decay takes 5 ps in ESR and ∼3 ps in bR. We discuss the similarity of the primary reactions of ESR and other retinal proteins.
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Affiliation(s)
| | - Tatiana B Feldman
- Emanuel Institute of Biochemical Physics, Moscow 119334, Russia.,Department of Biology, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Lada E Petrovskaya
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
| | - Oksana V Nekrasova
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
| | | | - Ivan V Shelaev
- Semenov Federal Research Center of Chemical Physics, Moscow 119991, Russia
| | - Fedor E Gostev
- Semenov Federal Research Center of Chemical Physics, Moscow 119991, Russia
| | | | - Irina B Kolchugina
- Department of Biology, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Dmitry A Dolgikh
- Department of Biology, Lomonosov Moscow State University, Moscow 119991, Russia.,Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
| | - Victor A Nadtochenko
- Semenov Federal Research Center of Chemical Physics, Moscow 119991, Russia.,Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Mikhail P Kirpichnikov
- Department of Biology, Lomonosov Moscow State University, Moscow 119991, Russia.,Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117997, Russia
| | - Mikhail A Ostrovsky
- Emanuel Institute of Biochemical Physics, Moscow 119334, Russia.,Department of Biology, Lomonosov Moscow State University, Moscow 119991, Russia
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6
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First-Principles Characterization of the Elusive I Fluorescent State and the Structural Evolution of Retinal Protonated Schiff Base in Bacteriorhodopsin. J Am Chem Soc 2019; 141:18193-18203. [DOI: 10.1021/jacs.9b08941] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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7
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Agathangelou D, Orozco-Gonzalez Y, Del Carmen Marín M, Roy PP, Brazard J, Kandori H, Jung KH, Léonard J, Buckup T, Ferré N, Olivucci M, Haacke S. Effect of point mutations on the ultrafast photo-isomerization of Anabaena sensory rhodopsin. Faraday Discuss 2019; 207:55-75. [PMID: 29388996 DOI: 10.1039/c7fd00200a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Anabaena sensory rhodopsin (ASR) is a particular microbial retinal protein for which light-adaptation leads to the ability to bind both the all-trans, 15-anti (AT) and the 13-cis, 15-syn (13C) isomers of the protonated Schiff base of retinal (PSBR). In the context of obtaining insight into the mechanisms by which retinal proteins catalyse the PSBR photo-isomerization reaction, ASR is a model system allowing to study, within the same protein, the protein-PSBR interactions for two different PSBR conformers at the same time. A detailed analysis of the vibrational spectra of AT and 13C, and their photo-products in wild-type ASR obtained through femtosecond (pump-) four-wave-mixing is reported for the first time, and compared to bacterio- and channelrhodopsin. As part of an extensive study of ASR mutants with blue-shifted absorption spectra, we present here a detailed computational analysis of the origin of the mutation-induced blue-shift of the absorption spectra, and identify electrostatic interactions as dominating steric effects that would entail a red-shift. The excited state lifetimes and isomerization reaction times (IRT) for the three mutants V112N, W76F, and L83Q are studied experimentally by femtosecond broadband transient absorption spectroscopy. Interestingly, in all three mutants, isomerization is accelerated for AT with respect to wild-type ASR, and this the more, the shorter the wavelength of maximum absorption. On the contrary, the 13C photo-reaction is slightly slowed down, leading to an inversion of the ESLs of AT and 13C, with respect to wt-ASR, in the blue-most absorbing mutant L83Q. Possible mechanisms for these mutation effects, and their steric and electrostatic origins are discussed.
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Affiliation(s)
- D Agathangelou
- University of Strasbourg, CNRS, Inst. de Physique et Chimie des Matériaux de Strasbourg, 67034 Strasbourg, France.
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8
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Barata-Morgado R, Sánchez ML, Muñoz-Losa A, Martín ME, Olivares Del Valle FJ, Aguilar MA. How Methylation Modifies the Photophysics of the Native All- trans-Retinal Protonated Schiff Base: A CASPT2/MD Study in Gas Phase and in Methanol. J Phys Chem A 2018; 122:3096-3106. [PMID: 29489369 DOI: 10.1021/acs.jpca.8b00773] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A comparison between the free-energy surfaces of the all- trans-retinal protonated Schiff base (RPSB) and its 10-methylated derivative in gas phase and methanol solution is performed at CASSCF//CASSCF and CASPT2//CASSCF levels. Solvent effects were included using the average solvent electrostatic potential from molecular dynamics method. This is a QM/MM (quantum mechanics/molecular mechanics) method that makes use of the mean field approximation. It is found that the methyl group bonded to C10 produces noticeable changes in the solution free-energy profile of the S1 excited state, mainly in the relative stability of the minimum energy conical intersections (MECIs) with respect to the Franck-Condon (FC) point. The conical intersections yielding the 9- cis and 11- cis isomers are stabilized while that yielding the 13- cis isomer is destabilized; in fact, it becomes inaccessible by excitation to S1. Furthermore, the planar S1 minimum is not present in the methylated compound. The solvent notably stabilizes the S2 excited state at the FC geometry. Therefore, if the S2 state has an effect on the photoisomerization dynamics, it must be because it permits the RPSB population to branch around the FC point. All these changes combine to speed up the photoisomerization in the 10-methylated compound with respect to the native compound.
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Affiliation(s)
- Rute Barata-Morgado
- Área de Química Física , University of Extremadura , Avda. Elvas s/n , Edif. José Ma Viguera Lobo 3a, planta, Badajoz 06006 , Spain
| | - M Luz Sánchez
- Área de Química Física , University of Extremadura , Avda. Elvas s/n , Edif. José Ma Viguera Lobo 3a, planta, Badajoz 06006 , Spain
| | - Aurora Muñoz-Losa
- Dpto. Didáctica de las Ciencias Experimentales y Matemáticas, Facultad de Formación del Profesorado , University of Extremadura , Avda. Universidad s/n , Cáceres 10003 , Spain
| | - M Elena Martín
- Área de Química Física , University of Extremadura , Avda. Elvas s/n , Edif. José Ma Viguera Lobo 3a, planta, Badajoz 06006 , Spain
| | - Francisco J Olivares Del Valle
- Área de Química Física , University of Extremadura , Avda. Elvas s/n , Edif. José Ma Viguera Lobo 3a, planta, Badajoz 06006 , Spain
| | - Manuel A Aguilar
- Área de Química Física , University of Extremadura , Avda. Elvas s/n , Edif. José Ma Viguera Lobo 3a, planta, Badajoz 06006 , Spain
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9
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Farag MH, Jansen TLC, Knoester J. The origin of absorptive features in the two-dimensional electronic spectra of rhodopsin. Phys Chem Chem Phys 2018; 20:12746-12754. [DOI: 10.1039/c8cp00638e] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A three-state three-mode model Hamiltonian reveals the origin of the absorptive features in the two-dimensional electronic spectra of rhodopsin.
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Affiliation(s)
- Marwa H. Farag
- University of Groningen
- Zernike Institute for Advanced Materials
- 9747 AG Groningen
- The Netherlands
| | - Thomas L. C. Jansen
- University of Groningen
- Zernike Institute for Advanced Materials
- 9747 AG Groningen
- The Netherlands
| | - Jasper Knoester
- University of Groningen
- Zernike Institute for Advanced Materials
- 9747 AG Groningen
- The Netherlands
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10
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Smitienko OA, Nekrasova OV, Kudriavtsev AV, Yakovleva MA, Shelaev IV, Gostev FE, Dolgikh DA, Kolchugina IB, Nadtochenko VA, Kirpichnikov MP, Feldman TB, Ostrovsky MA. Femtosecond and picosecond dynamics of recombinant bacteriorhodopsin primary reactions compared to the native protein in trimeric and monomeric forms. BIOCHEMISTRY (MOSCOW) 2017; 82:490-500. [DOI: 10.1134/s0006297917040113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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11
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Iyer ESS, Misra R, Maity A, Liubashevski O, Sudo Y, Sheves M, Ruhman S. Temperature Independence of Ultrafast Photoisomerization in Thermophilic Rhodopsin: Assessment versus Other Microbial Proton Pumps. J Am Chem Soc 2016; 138:12401-7. [DOI: 10.1021/jacs.6b05002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Ramprasad Misra
- Department
of Organic Chemistry, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Arnab Maity
- Institute
of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190501, Israel
| | - Oleg Liubashevski
- Institute
of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190501, Israel
| | - Yuki Sudo
- Division
of Pharmaceutical sciences, Okayama University, Kita-Ku, Okayama 700-0082, Japan
| | - Mordechai Sheves
- Department
of Organic Chemistry, The Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sanford Ruhman
- Institute
of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190501, Israel
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12
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Roy P, Kantor-Uriel N, Mishra D, Dutta S, Friedman N, Sheves M, Naaman R. Spin-Controlled Photoluminescence in Hybrid Nanoparticles Purple Membrane System. ACS NANO 2016; 10:4525-4531. [PMID: 27018195 PMCID: PMC4850504 DOI: 10.1021/acsnano.6b00333] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 03/27/2016] [Indexed: 05/29/2023]
Abstract
Spin-dependent photoluminescence (PL) quenching of CdSe nanoparticles (NPs) has been explored in the hybrid system of CdSe NP purple membrane, wild-type bacteriorhodopsin (bR) thin film on a ferromagnetic (Ni-alloy) substrate. A significant change in the PL intensity from the CdSe NPs has been observed when spin-specific charge transfer occurs between the retinal and the magnetic substrate. This feature completely disappears in a bR apo membrane (wild-type bacteriorhodopsin in which the retinal protein covalent bond was cleaved), a bacteriorhodopsin mutant (D96N), and a bacteriorhodopsin bearing a locked retinal chromophore (isomerization of the crucial C13═C14 retinal double bond was prevented by inserting a ring spanning this bond). The extent of spin-dependent PL quenching of the CdSe NPs depends on the absorption of the retinal, embedded in wild-type bacteriorhodopsin. Our result suggests that spin-dependent charge transfer between the retinal and the substrate controls the PL intensity from the NPs.
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Affiliation(s)
- Partha Roy
- Department
of Chemical Physics and Department of Organic Chemistry, Weizmann Institute, Rehovot 76100, Israel
| | - Nirit Kantor-Uriel
- Department
of Chemical Physics and Department of Organic Chemistry, Weizmann Institute, Rehovot 76100, Israel
| | - Debabrata Mishra
- Department
of Chemical Physics and Department of Organic Chemistry, Weizmann Institute, Rehovot 76100, Israel
| | - Sansa Dutta
- Department
of Chemical Physics and Department of Organic Chemistry, Weizmann Institute, Rehovot 76100, Israel
| | - Noga Friedman
- Department
of Chemical Physics and Department of Organic Chemistry, Weizmann Institute, Rehovot 76100, Israel
| | - Mordechai Sheves
- Department
of Chemical Physics and Department of Organic Chemistry, Weizmann Institute, Rehovot 76100, Israel
| | - Ron Naaman
- Department
of Chemical Physics and Department of Organic Chemistry, Weizmann Institute, Rehovot 76100, Israel
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13
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Cheminal A, Léonard J, Kim SY, Jung KH, Kandori H, Haacke S. 100 fs photo-isomerization with vibrational coherences but low quantum yield in Anabaena Sensory Rhodopsin. Phys Chem Chem Phys 2015; 17:25429-39. [DOI: 10.1039/c5cp04353k] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Counter-intuitive photochemistry: in Anabaena Sensory Rhodopsin, the retinal 13-cis isomer isomerizes much faster than all-trans ASR, but with a 3-times lower quantum yield.
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Affiliation(s)
- Alexandre Cheminal
- Institut de Physique et Chimie des Matériaux de Strasbourg & Labex NIE
- Université de Strasbourg – CNRS
- 67034 Strasbourg
- France
| | - Jérémie Léonard
- Institut de Physique et Chimie des Matériaux de Strasbourg & Labex NIE
- Université de Strasbourg – CNRS
- 67034 Strasbourg
- France
| | - So-Young Kim
- Department of Life Science and Institute of Biological Interfaces
- Sogang University
- Mapo-Gu
- South Korea
| | - Kwang-Hwan Jung
- Department of Life Science and Institute of Biological Interfaces
- Sogang University
- Mapo-Gu
- South Korea
| | - Hideki Kandori
- Department of Frontier Materials
- Nagoya Institute of Technology
- Showa-ku
- Japan
| | - Stefan Haacke
- Institut de Physique et Chimie des Matériaux de Strasbourg & Labex NIE
- Université de Strasbourg – CNRS
- 67034 Strasbourg
- France
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14
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Mukhopadhyay S, Cohen SR, Marchak D, Friedman N, Pecht I, Sheves M, Cahen D. Nanoscale electron transport and photodynamics enhancement in lipid-depleted bacteriorhodopsin monomers. ACS NANO 2014; 8:7714-7722. [PMID: 25003581 DOI: 10.1021/nn500202k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Potential future use of bacteriorhodopsin (bR) as a solid-state electron transport (ETp) material requires the highest possible active protein concentration. To that end we prepared stable monolayers of protein-enriched bR on a conducting HOPG substrate by lipid depletion of the native bR. The ETp properties of this construct were then investigated using conducting probe atomic force microscopy at low bias, both in the ground dark state and in the M-like intermediate configuration, formed upon excitation by green light. Photoconductance modulation was observed upon green and blue light excitation, demonstrating the potential of these monolayers as optoelectronic building blocks. To correlate protein structural changes with the observed behavior, measurements were made as a function of pressure under the AFM tip, as well as humidity. The junction conductance is reversible under pressure changes up to ∼300 MPa, but above this pressure the conductance drops irreversibly. ETp efficiency is enhanced significantly at >60% relative humidity, without changing the relative photoactivity significantly. These observations are ascribed to changes in protein conformation and flexibility and suggest that improved electron transport pathways can be generated through formation of a hydrogen-bonding network.
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Kraack JP, Buckup T, Hampp N, Motzkus M. Ground- and Excited-State Vibrational Coherence Dynamics in Bacteriorhodopsin Probed With Degenerate Four-Wave-Mixing Experiments. Chemphyschem 2011; 12:1851-9. [DOI: 10.1002/cphc.201100032] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 05/24/2011] [Indexed: 11/06/2022]
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16
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Kraack JP, Buckup T, Motzkus M. Vibrational analysis of excited and ground electronic states of all-trans retinal protonated Schiff-bases. Phys Chem Chem Phys 2011; 13:21402-10. [DOI: 10.1039/c1cp22245g] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Aborted double bicycle-pedal isomerization with hydrogen bond breaking is the primary event of bacteriorhodopsin proton pumping. Proc Natl Acad Sci U S A 2010; 107:20172-7. [PMID: 21048087 DOI: 10.1073/pnas.1007000107] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Quantum mechanics/molecular mechanics calculations based on ab initio multiconfigurational second order perturbation theory are employed to construct a computer model of Bacteriorhodopsin that reproduces the observed static and transient electronic spectra, the dipole moment changes, and the energy stored in the photocycle intermediate K. The computed reaction coordinate indicates that the isomerization of the retinal chromophore occurs via a complex motion accounting for three distinct regimes: (i) production of the excited state intermediate I, (ii) evolution of I toward a conical intersection between the excited state and the ground state, and (iii) formation of K. We show that, during stage ii, a space-saving mechanism dominated by an asynchronous double bicycle-pedal deformation of the C10═C11─C12═C13─C14═N moiety of the chromophore dominates the isomerization. On this same stage a N─H/water hydrogen bond is weakened and initiates a breaking process that is completed during stage iii.
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Bismuth O, Komm P, Friedman N, Eliash T, Sheves M, Ruhman S. Deciphering Excited State Evolution in Halorhodopsin with Stimulated Emission Pumping. J Phys Chem B 2010; 114:3046-51. [DOI: 10.1021/jp910853n] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Oshrat Bismuth
- Institute of Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel, and Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Pavel Komm
- Institute of Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel, and Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Noga Friedman
- Institute of Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel, and Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tamar Eliash
- Institute of Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel, and Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Mordechai Sheves
- Institute of Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel, and Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sanford Ruhman
- Institute of Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel, and Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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Comparing photochemistry of n- and tert-butylamine all-trans retinal protonated Schiff-base: Effects of C N configurational inhomogeneity. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.08.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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20
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Andresen ER, Hamm P. Site-specific difference 2D-IR spectroscopy of bacteriorhodopsin. J Phys Chem B 2009; 113:6520-7. [PMID: 19358550 DOI: 10.1021/jp810397u] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We demonstrate the extension of the principle of difference Fourier transform infrared (FTIR) spectroscopy to difference 2D-IR spectroscopy. To this end, we measure difference 2D-IR spectra of the protein bacteriorhodopsin in its early J- and K-intermediates. By comparing with the static 2D-IR spectrum of the protonated Schiff base of all-trans retinal, we demonstrate that the 2D-IR spectrum of the all-trans retinal chromophore in bacteriorhodopsin can be measured with the background from the remainder of the protein completely suppressed. We discuss several models to interpret the detailed line shape of the difference 2D-IR spectrum.
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Affiliation(s)
- Esben Ravn Andresen
- Physikalisch-Chemisches Institut, Universitat Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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21
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Shim S, Dasgupta J, Mathies RA. Femtosecond Time-Resolved Stimulated Raman Reveals the Birth of Bacteriorhodopsin’s J and K Intermediates. J Am Chem Soc 2009; 131:7592-7. [DOI: 10.1021/ja809137x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sangdeok Shim
- Department of Chemistry, University of California, Berkeley, California 94720
| | - Jyotishman Dasgupta
- Department of Chemistry, University of California, Berkeley, California 94720
| | - Richard A. Mathies
- Department of Chemistry, University of California, Berkeley, California 94720
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22
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Gross R, Schumann C, Wolf MMN, Herbst J, Diller R, Friedman N, Sheves M. Ultrafast Protein Conformational Alterations in Bacteriorhodopsin and Its Locked Analogue BR5.12. J Phys Chem B 2009; 113:7851-60. [PMID: 19422251 DOI: 10.1021/jp810042f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ruth Gross
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Christian Schumann
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Matthias M. N. Wolf
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Johannes Herbst
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Rolf Diller
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Noga Friedman
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | - Mordechai Sheves
- Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel
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23
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Carotenoid deactivation in an artificial light-harvesting complex via a vibrationally hot ground state. Chem Phys 2009. [DOI: 10.1016/j.chemphys.2009.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
Functions of biologically active molecules are frequently initiated by elementary chemical reactions such as energy and electron transfer, cis-trans isomerizations, and proton transfer. The nature of these reactions generally makes them very fast and efficient, occurring on picosecond and femtosecond timescales. Ultrafast spectroscopy has played an important role in the study of a number of biological processes and has provided unique information about several of nature's responses to light. Here I review the current understanding of light-energy collection and conversion in photosynthesis, the function of carotenoid molecules in photosynthesis, and the primary light-initiated reactions of the photoreceptors rhodopsin, bacteriorhodopsin, photoactive yellow protein, phytochrome, and a new type of blue-light receptor based on flavin chromophores.
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Affiliation(s)
- Villy Sundström
- Department of Chemical Physics, Lund University, S-221 00 Lund, Sweden.
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25
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Wu Y, Zhong S, Ai X, Hu K, Zhang J. Ultrafast isomerization dynamics of retinal in bacteriorhodopsin as revealed by femtosecond absorption spectroscopy. Sci Bull (Beijing) 2008. [DOI: 10.1007/s11434-008-0283-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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26
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Kobayashi T, Yabushita A, Saito T, Ohtani H, Tsuda M. Sub-5-fs real-time spectroscopy of transition states in bacteriorhodopsin during retinal isomerization. Photochem Photobiol 2007; 83:363-8. [PMID: 17132067 DOI: 10.1562/2006-08-19-ir-1006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
By using a sub-5-fs visible laser pulse, we have made the first observation of the vibrational spectra of the transition state during trans-cis isomerization in the retinal chromophore of bacteriorhodopsin (bR(S68). No instant isomerization of the retinal occurs in spite of electron promotion from the bonding pi-orbital to the anti-bonding pi*-orbital. The difference between the in-plane and out-of-plane vibrational frequencies (about 1150-1250 and 900-1000 cm(-1), respectively) is reduced during the first time period. The vibrational spectra after this period became very broad and weak and are ascribed to a "silent state." The silent state lasts for 700-900 fs until the chromophore isomerizes to the cis-C13 = C14 conformation. The frequency of the C = C stretching mode was modulated by the torsion mode of the C13 = C14 double bond with a period of 200 fs. The modulation was clearly observed for four to five periods. Using the empirical equation for the relation between bond length and stretching frequency, we determined the transitional C = C bond length with about 0.01 angstroms accuracy during the torsion motion around the double bond with 1-fs time resolution.
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Affiliation(s)
- Takayoshi Kobayashi
- Department of Physics, Graduate School of Science, University of Tokyo, Bunkyo, Tokyo, Japan.
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27
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Losi A, Michler I, Gärtner W, Braslavsky SE. Time-resolved Thermodynamic Changes Photoinduced in 5,12-trans-locked Bacteriorhodopsin. Evidence that Retinal Isomerization is Required for Protein Activation¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2000)0720590trtcpi2.0.co2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Kahan A, Nahmias O, Friedman N, Sheves M, Ruhman S. Following Photoinduced Dynamics in Bacteriorhodopsin with 7-fs Impulsive Vibrational Spectroscopy. J Am Chem Soc 2006; 129:537-46. [PMID: 17227016 DOI: 10.1021/ja064910d] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sub-10-fs laser pulses are used to impulsively photoexcite bacteriorhodopsin (BR) suspensions and probe the evolution of the resulting vibrational wave packets. Fourier analysis of the spectral modulations induced by transform-limited as well as linearly chirped excitation pulses allows the delineation of excited- and ground-state contributions to the data. On the basis of amplitude and phase variations of the modulations as a function of the dispersed probe wavelength, periodic modulations in absorption above 540 nm are assigned to ground-state vibrational coherences induced by resonance impulsive Raman spectral activity (RISRS). Probing at wavelengths below 540 nm-the red edge of the intense excited-state absorption band-uncovers new vibrational features which are accordingly assigned to wave packet motions along bound coordinates on the short-lived reactive electronic surface. They consist of high- and low-frequency shoulders adjacent to the strong C=C stretching and methyl rock modes, respectively, which have ground-state frequencies of 1008 and 1530 cm-1. Brief activity centered at approximately 900 cm-1, which is characteristic of ground-state HOOP modes, and strong modulations in the torsional frequency range appear as well. Possible assignments of the bands and their implication to photoinduced reaction dynamics in BR are discussed. Reasons for the absence of similar signatures in the pump-probe spectral modulations at longer probing wavelengths are considered as well.
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Affiliation(s)
- Anat Kahan
- Department of Physical Chemistry and the Farkas Center for Light Induced Processes, Hebrew University, Jerusalem 91904, Israel
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29
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Send R, Sundholm D. The Role of the β-Ionone Ring in the Photochemical Reaction of Rhodopsin. J Phys Chem A 2006; 111:27-33. [PMID: 17201384 DOI: 10.1021/jp065510f] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Time-dependent density functional theory (TDDFT) calculations on the photoabsorption process of the 11-cis retinal protonated Schiff base (PSB) chromophore show that the Franck-Condon relaxation of the first excited state of the chromophore involves a torsional twist motion of the beta-ionone ring relative to the conjugated retinyl chain. For the ground state, the beta-ionone ring and the retinyl chain of the free retinal PSB chromophore form a -40 degrees dihedral angle as compared to -94 degrees for the first excited state. The double bonds of the retinal are shorter for the fully optimized structure of the excited state than for the ground state suggesting a higher cis-trans isomerization barrier for the excited state than for the ground state. According to the present TDDFT calculations, the excitation of the retinal PSB chromophore does not primarily lead to a reaction along the cis-trans torsional coordinate at the C11-C12 bond. The activation of the isomerization center seems to occur at a later stage of the photo reaction. The results obtained at the TDDFT level are supported by second-order Møller-Plesset (MP2) and approximate singles and doubles-coupled cluster (CC2) calculations on retinal chromophore models; the MP2 and CC2 calculations yield for them qualitatively the same ground state and excited-state structures as obtained in the density functional theory and TDDFT calculations.
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Affiliation(s)
- Robert Send
- Institut für Physikalische Chemie, Universität Karlsruhe, Kaiserstrasse 12, D-76128 Karlsruhe, Germany
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30
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Prokhorenko VI, Nagy AM, Waschuk SA, Brown LS, Birge RR, Miller RJD. Coherent Control of Retinal Isomerization in Bacteriorhodopsin. Science 2006; 313:1257-61. [PMID: 16946063 DOI: 10.1126/science.1130747] [Citation(s) in RCA: 217] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Optical control of the primary step of photoisomerization of the retinal molecule in bacteriorhodopsin from the all-trans to the 13-cis state was demonstrated under weak field conditions (where only 1 of 300 retinal molecules absorbs a photon during the excitation cycle) that are relevant to understanding biological processes. By modulating the phases and amplitudes of the spectral components in the photoexcitation pulse, we showed that the absolute quantity of 13-cis retinal formed upon excitation can be enhanced or suppressed by +/-20% of the yield observed using a short transform-limited pulse having the same actinic energy. The shaped pulses were shown to be phase-sensitive at intensities too low to access different higher electronic states, and so these pulses apparently steer the isomerization through constructive and destructive interference effects, a mechanism supported by observed signatures of vibrational coherence. These results show that the wave properties of matter can be observed and even manipulated in a system as large and complex as a protein.
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Affiliation(s)
- Valentyn I Prokhorenko
- Institute for Optical Sciences, Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, M5S3H6, Toronto, Ontario, Canada
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Schenkl S, van Mourik F, Friedman N, Sheves M, Schlesinger R, Haacke S, Chergui M. Insights into excited-state and isomerization dynamics of bacteriorhodopsin from ultrafast transient UV absorption. Proc Natl Acad Sci U S A 2006; 103:4101-6. [PMID: 16537491 PMCID: PMC1449653 DOI: 10.1073/pnas.0506303103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A visible-pump/UV-probe transient absorption is used to characterize the ultrafast dynamics of bacteriorhodopsin with 80-fs time resolution. We identify three spectral components in the 265- to 310-nm region, related to the all-trans retinal, tryptophan (Trp)-86 and the isomerized photoproduct, allowing us to map the dynamics from reactants to products, along with the response of Trp amino acids. The signal of the photoproduct appears with a time delay of approximately 250 fs and is characterized by a steep rise ( approximately 150 fs), followed by additional rise and decay components, with time scales characteristic of the J intermediate. The delayed onset and the steep rise point to an impulsive formation of a transition state on the way to isomerization. We argue that this impulsive formation results from a splitting of a wave packet of torsional modes on the potential surface at the branching between the all-trans and the cis forms. Parallel to these dynamics, the signal caused by Trp response rises in approximately 200 fs, because of the translocation of charge along the conjugate chain, and possible mechanisms are presented, which trigger isomerization.
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Affiliation(s)
- S. Schenkl
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
| | - F. van Mourik
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
| | - N. Friedman
- Departments of Organic Chemistry and Chemical Services, The Weizmann Institute of Sciences, Rehovot 76100, Israel; and
| | - M. Sheves
- Departments of Organic Chemistry and Chemical Services, The Weizmann Institute of Sciences, Rehovot 76100, Israel; and
| | - R. Schlesinger
- Institute for Structural Biology, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - S. Haacke
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
| | - M. Chergui
- *Laboratoire de Spectroscopie Ultrarapide, Institut des Sciences et Ingeniérie Chimiques, Faculté des Sciences de Base, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne-Dorigny, Switzerland
- To whom correspondence should be addressed. E-mail:
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Zgrablić G, Voïtchovsky K, Kindermann M, Haacke S, Chergui M. Ultrafast excited state dynamics of the protonated Schiff base of all-trans retinal in solvents. Biophys J 2005; 88:2779-88. [PMID: 15792984 PMCID: PMC1305373 DOI: 10.1529/biophysj.104.046094] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present a comparative study of the ultrafast photophysics of all-trans retinal in the protonated Schiff base form in solvents with different polarities and viscosities. Steady-state spectra of retinal in the protonated Schiff base form show large absorption-emission Stokes shifts (6500-8100 cm(-1)) for both polar and nonpolar solvents. Using a broadband fluorescence up-conversion experiment, the relaxation kinetics of fluorescence is investigated with 120 fs time resolution. The time-zero spectra already exhibit a Stokes-shift of approximately 6000 cm(-1), indicating depopulation of the Franck-Condon region in < or =100 fs. We attribute it to relaxation along skeletal stretching. A dramatic spectral narrowing is observed on a 150 fs timescale, which we assign to relaxation from the S(2) to the S(1) state. Along with the direct excitation of S(1), this relaxation populates different quasistationary states in S(1), as suggested from the existence of three distinct fluorescence decay times with different decay associated spectra. A 0.5-0.65 ps decay component is observed, which may reflect the direct repopulation of the ground state, in line with the small isomerization yield in solvents. Two longer decay components are observed and are attributed to torsional motion leading to photo-isomerization. The various decay channels show little or no dependence with respect to the viscosity or dielectric constant of the solvents. This suggests that in the protein, the bond selectivity of isomerization is mainly governed by steric effects.
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Affiliation(s)
- Goran Zgrablić
- Laboratoire de Spectroscopie Ultrarapide, Ecole Polytechnique Fédérale de Lausanne, Institute of Chemical Sciences and Engineering, FSB-BSP, CH-1015 Lausanne-Dorigny, Switzerland
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Zadok U, Klare JP, Engelhard M, Sheves M. The hydroxylamine reaction of sensory rhodopsin II: light-induced conformational alterations with C13=C14 nonisomerizable pigment. Biophys J 2005; 89:2610-7. [PMID: 16085771 PMCID: PMC1366761 DOI: 10.1529/biophysj.105.065631] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sensory rhodopsin II, a repellent phototaxis receptor from Natronomonas (Natronobacterium) pharaonis (NpSRII), forms a complex with its cognate transducer (NpHtrII). In micelles the two proteins form a 1:1 heterodimer, whereas in membranes they assemble to a 2:2 complex. Similarly to other retinal proteins, sensory rhodopsin II undergoes a bleaching reaction with hydroxylamine in the dark which is markedly catalyzed by light. The reaction involves cleavage of the protonated Schiff base bond which covalently connects the retinal chromophore to the protein. The light acceleration reflects protein conformation alterations, at least in the retinal binding site, and thus allows for detection of these changes in various conditions. In this work we have followed the hydroxylamine reaction at different temperatures with and without the cognate transducer. We have found that light irradiation reduces the activation energy of the hydroxylamine reaction as well as the frequency factor. A similar effect was found previously for bacteriorhodopsin. The interaction with the transducer altered the light effect both in detergent and membranes. The transducer interaction decreased the apparent light effect on the energy of activation and the frequency factor in detergent but increased it in membranes. In addition, we have employed an artificial pigment derived from a retinal analog in which the critical C13=C14 double bond is locked by a rigid ring structure preventing its isomerization. We have observed light enhancement of the reaction rate and reduction of the energy of activation as well as the frequency factor, despite the fact that this pigment does not experience C13=C14 double bond isomerization. It is suggested that retinal excited state polarization caused by light absorption of the "locked" pigment polarizes the protein and triggers relatively long-lived protein conformational alterations.
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Affiliation(s)
- U Zadok
- Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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35
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Primary events in the bacteriorhodopsin photocycle: Torsional vibrational dephasing in the first excited electronic state. Chem Phys 2005. [DOI: 10.1016/j.chemphys.2004.12.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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36
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Schmidt B, Sobotta C, Heinz B, Laimgruber S, Braun M, Gilch P. Excited-state dynamics of bacteriorhodopsin probed by broadband femtosecond fluorescence spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1706:165-73. [PMID: 15620377 DOI: 10.1016/j.bbabio.2004.10.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 10/04/2004] [Accepted: 10/20/2004] [Indexed: 10/26/2022]
Abstract
The impact of varying excitation densities (approximately 0.3 to approximately 40 photons per molecule) on the ultrafast fluorescence dynamics of bacteriorhodopsin has been studied in a wide spectral range (630-900 nm). For low excitation densities, the fluorescence dynamics can be approximated biexponentially with time constants of <0.15 and approximately 0.45 ps. The spectrum associated with the fastest time constant peaks at 650 nm, while the 0.45 ps component is most prominent at 750 nm. Superimposed on these kinetics is a shift of the fluorescence maximum with time (dynamic Stokes shift). Higher excitation densities alter the time constants and their amplitudes. These changes are assigned to multi-photon absorptions.
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Affiliation(s)
- B Schmidt
- Department für Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, D-80538 Munich, Germany
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37
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Balzer B, Stock G. Transient Spectral Features of a cis−trans Photoreaction in the Condensed Phase: A Model Study. J Phys Chem A 2004. [DOI: 10.1021/jp048965i] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Birgit Balzer
- Institute of Physical and Theoretical Chemistry, J. W. Goethe University, Marie-Curie-Strasse 11, D-60439 Frankfurt, Germany
| | - Gerhard Stock
- Institute of Physical and Theoretical Chemistry, J. W. Goethe University, Marie-Curie-Strasse 11, D-60439 Frankfurt, Germany
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38
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Abramczyk H. Femtosecond primary events in bacteriorhodopsin and its retinal modified analogs: Revision of commonly accepted interpretation of electronic spectra of transient intermediates in the bacteriorhodopsin photocycle. J Chem Phys 2004; 120:11120-32. [PMID: 15268142 DOI: 10.1063/1.1737731] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Femtosecond primary events in bacteriorhodopsin (BR) and its retinal modified analogs are discussed. Ultrafast time resolved electronic spectra of the primary intermediates induced in the BR photocycle are discussed along with spectral and kinetic inconsistencies of the previous models proposed in the literature. The theoretical model proposed in this paper based on vibrational coupling between the electronic transition of the chromophore and intramolecular vibrational modes allows us to calculate the equilibrium electronic absorption band shape and the hole burning profiles. The model is able to rationalize the complex pattern of behavior for the primary events in BR and explain the origin of the apparent inconsistencies between the experiment and the previous theoretical models. The model presented in the paper is based on the anharmonic coupling assumption in the adiabatic approximation using the canonical transformation method for diagonalization of the vibrational Hamiltonian instead of the commonly used perturbation theory. The electronic transition occurs between the Born-Oppenheimer potential energy surfaces with the electron involved in the transition being coupled to the intramolecular vibrational modes of the molecule (chromophore). The relaxation of the excited state occurs by indirect damping (dephasing) mechanisms. The indirect dephasing is governed by the time evolution of the anharmonic coupling constant driven by the resonance energy exchange between the intramolecular vibrational mode and the bath. The coupling with the intramolecular vibrational modes results in the Franck-Condon progression of bands that are broadened due to the vibrational dephasing mechanisms. The electronic absorption line shape has been calculated based on the linear response theory whereas the third order nonlinear response functions have been used to analyze the hole burning profiles obtained from the pump-probe time-resolved measurements. The theoretical treatment proposed in this paper provides a basis for a substantial revision of the commonly accepted interpretation of the primary events in the BR photocycle that exists in the literature.
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Affiliation(s)
- Halina Abramczyk
- Technical University, Department of Chemistry, Laboratory of Molecular Laser Spectroscopy at IARC, Wroblewskiego 15 Street, 93-590 Lodz, Poland.
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39
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Groma GI, Colonna A, Lambry JC, Petrich JW, Váró G, Joffre M, Vos MH, Martin JL. Resonant optical rectification in bacteriorhodopsin. Proc Natl Acad Sci U S A 2004; 101:7971-5. [PMID: 15148391 PMCID: PMC419541 DOI: 10.1073/pnas.0306789101] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The relative role of retinal isomerization and microscopic polarization in the phototransduction process of bacteriorhodopsin is still an open question. It is known that both processes occur on an ultrafast time scale. The retinal trans-->cis photoisomerization takes place on the time scale of a few hundred femtoseconds. On the other hand, it has been proposed that the primary light-induced event is a sudden polarization of the retinal environment, although there is no direct experimental evidence for femtosecond charge displacements, because photovoltaic techniques cannot be used to detect charge movements faster than picoseconds. Making use of the known high second-order susceptibility chi(2) of retinal in proteins, we have used a nonlinear technique, interferometric detection of coherent infrared emission, to study macroscopically oriented bacteriorhodopsin-containing purple membranes. We report and characterize impulsive macroscopic polarization of these films by optical rectification of an 11-fs visible light pulse in resonance with the optical transition. This finding provides direct evidence for charge separation as a precursor event for subsequent functional processes. A simple two-level model incorporating the resonant second-order optical properties of retinal, which are known to be a requirement for functioning of bacteriorhodopsin, is used to describe the observations. In addition to the electronic response, long-lived infrared emission at specific frequencies was observed, reflecting charge movements associated with vibrational motions. The simultaneous and phase-sensitive observation of both the electronic and vibrational signals opens the way to study the transduction of the initial polarization into structural dynamics.
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Affiliation(s)
- Géza I Groma
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, H-6726, Hungary
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40
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Cembran A, Bernardi F, Olivucci M, Garavelli M. Excited-state singlet manifold and oscillatory features of a nonatetraeniminium retinal chromophore model. J Am Chem Soc 2003; 125:12509-19. [PMID: 14531695 DOI: 10.1021/ja030215j] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this paper we use ab initio multireference Møller-Plesset second-order perturbation theory computations to map the first five singlet states (S(0), S(1), S(2), S(3), and S(4)) along the initial part of the photoisomerization coordinate for the isolated rhodopsin chromophore model 4-cis-gamma-methylnona-2,4,6,8-tetraeniminium cation. We show that this information not only provides an explanation for the spectral features associated to the chromophore in solution but also, subject to a tentative hypothesis on the effect of the protein cavity, may be employed to explain/assign the ultrafast near-IR excited-state absorption, stimulated emission, and transient excited-state absorption bands observed in rhodopsin proteins (e.g. rhodopsin and bacteriorhodopsin). We also show that the results of vibrational frequency computations reveal a general structure for the first (S(1)) excited-state energy surface of PSBs that is consistent with the existence of the coherent oscillatory motions observed both in solution and in bacteriorhodopsin.
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Affiliation(s)
- Alessandro Cembran
- Dipartimento di Chimica, Università di Siena, via Aldo Moro, Siena, I-53100 Italy
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41
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Comparing photoinduced vibrational coherences in bacteriorhodopsin and in native and locked retinal protonated Schiff bases. Chem Phys Lett 2003. [DOI: 10.1016/j.cplett.2003.10.038] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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42
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Terentis AC, Zhou Y, Atkinson GH, Ujj L. Picosecond Time-Resolved Coherent Anti-Stokes Raman Spectroscopy of the Artificial Bacteriorhodopsin Pigment, BR6.11. J Phys Chem A 2003. [DOI: 10.1021/jp030612g] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrew C. Terentis
- Department of Chemistry and Optical Sciences Center, University of Arizona, Tucson, Arizona 85721
| | - Yidong Zhou
- Department of Chemistry and Optical Sciences Center, University of Arizona, Tucson, Arizona 85721
| | - George H. Atkinson
- Department of Chemistry and Optical Sciences Center, University of Arizona, Tucson, Arizona 85721
| | - Laszlo Ujj
- Department of Physics, University of West Florida, Pensacola, Florida 32514
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43
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Wang J, Link S, Heyes CD, El-Sayed MA. Comparison of the dynamics of the primary events of bacteriorhodopsin in its trimeric and monomeric states. Biophys J 2002; 83:1557-66. [PMID: 12202380 PMCID: PMC1302253 DOI: 10.1016/s0006-3495(02)73925-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In this paper, femtosecond pump-probe spectroscopy in the visible region of the spectrum has been used to examine the ultrafast dynamics of the retinal excited state in both the native trimeric state and the monomeric state of bacteriorhodopsin (bR). It is found that the excited state lifetime (probed at 490 nm) increases only slightly upon the monomerization of bR. No significant kinetic difference is observed in the recovery process of the bR ground state probed at 570 nm nor in the fluorescent state observed at 850 nm. However, an increase in the relative amplitude of the slow component of bR excited state decay is observed in the monomer, which is due to the increase in the concentration of the 13-cis retinal isomer in the ground state of the light-adapted bR monomer. Our data indicate that when the protein packing around the retinal is changed upon bR monomerization, there is only a subtle change in the retinal potential surface, which is dependent on the charge distribution and the dipoles within the retinal-binding cavity. In addition, our results show that 40% of the excited state bR molecules return to the ground state on three different time scales: one-half-picosecond component during the relaxation of the excited state and the formation of the J intermediate, a 3-ps component as the J changes to the K intermediate where retinal photoisomerization occurs, and a subnanosecond component during the photocycle.
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Affiliation(s)
- Jianping Wang
- Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 USA
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44
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Wang J, El-Sayed MA. Time-resolved long-lived infrared emission from bacteriorhodopsin during its photocycle. Biophys J 2002; 83:1589-94. [PMID: 12202383 PMCID: PMC1302256 DOI: 10.1016/s0006-3495(02)73928-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The infrared emission observed below 2000 cm(-1) upon exciting retinal in bacteriorhodopsin (bR) is found to have a rise time in the submicrosecond time regime and to relax with two exponential components on the submillisecond to millisecond time scale. These time scales, together with the assignment of this emission to hot vibrations from the all-trans retinal (in bR) and the 13-cis retinal (in the K intermediate), support the recent assignment of the J-intermediate as an electronically excited species (Atkinson et al., J. Phys. Chem. A. 104:4130-4139, 2000) rather than a vibrationally hot K intermediate. A discussion of these time scales of the observed infrared emission is given in terms of the competition between radiative and nonradiative relaxation processes of the vibrational states involved.
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Affiliation(s)
- Jianping Wang
- Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 USA
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45
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Ruhman S, Hou B, Friedman N, Ottolenghi M, Sheves M. Following evolution of bacteriorhodopsin in its reactive excited state via stimulated emission pumping. J Am Chem Soc 2002; 124:8854-8. [PMID: 12137538 DOI: 10.1021/ja026426q] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
New information concerning the photochemical dynamics of bacteriorhodopsin (BR) is obtained by impulsively stimulating emission from the reactive fluorescent state. Depletion of the excited-state fluorescence leads to an equal reduction in production of later photoproducts. Accordingly, chromophores which are forced back to the ground state via emission do not continue on in the photocycle, conclusively demonstrating that the fluorescent state is a photocycle intermediate. The insensitivity of depletion dynamics to the "dump" pulse timing, throughout the fluorescent states lifetime, and the biological inactivity of the dumped population suggest that the fluorescent-state structure is constant, well-defined, and significantly different than that where crossing to the ground state takes place naturally. In conjunction with conclusions from comparing the photophysics of BR with those of synthetic analogues containing "locked" retinals, present results show that large-amplitude torsion around C13=C14 is required to go between the above structures.
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Affiliation(s)
- Sanford Ruhman
- Department of Physical Chemistry and The Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel.
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46
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Haacke S, Schenkl S, Vinzani S, Chergui M. Femtosecond and picosecond fluorescence of native bacteriorhodopsin and a nonisomerizing analog. Biopolymers 2002; 67:306-9. [PMID: 12012454 DOI: 10.1002/bip.10092] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The spectrally and temporally resolved fluorescence properties of native bacteriorhodopsin (bR) and bR reconstituted with a nonisomerizing analog of the retinal Schiff base (bR5.12) are examined. The first attempt to experimentally monitor the excited state relaxation processes in both type of pigments using ultrafast fluorescence spectroscopy is reported. The fluorescence is emitted from retinal molecules in an all-trans configuration. Substantial energy relaxation involves very fast intramolecular and intermolecular vibrational modes and these are shown to occur on a time scale faster than isomerization. The possible contribution of dielectric interaction between the retinal Schiff base and the protein environment for the excited state energy relaxation is discussed.
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Affiliation(s)
- S Haacke
- Institut de Physique de la Matière Condensée, Université de Lausanne, CH-1015, Switzerland.
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47
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Schenkl S, Portuondo E, Zgrablić G, Chergui M, Haacke S, Friedman N, Sheves M. Ultrafast energy relaxation in bacteriorhodopsin studied by time-integrated fluorescence. Phys Chem Chem Phys 2002. [DOI: 10.1039/b205453a] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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48
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Parusel AB, Pohorille A. A semiempirical study of the optimized ground and excited state potential energy surfaces of retinal and its protonated Schiff base. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2001; 65:13-21. [PMID: 11748000 DOI: 10.1016/s1011-1344(01)00238-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The electronic ground and first excited states of retinal and its Schiff base are optimized for the first time using the semiempirical AM1 Hamiltonian. The barrier for rotation about the C(11)-C(12) double bond is characterized by variation of both the twist angle delta(C(10)-C(11)-C(12)-C(13)) and the bond length d(C(11)-C(12)). The potential energy surface is obtained by varying these two parameters. The calculated ground state rotational barrier is equal to 15.6 kcal/mol for retinal and 20.5 kcal/mol for its Schiff base. The all-trans conformation is more stable by 3.7 kcal/mol than the 11-cis geometry. For the first excited state, S(1,) the 90 degrees twisted geometry represents a saddle point for retinal with the rotational barrier of 14.6 kcal/mol. In contrast, this conformation is an energy minimum for the Schiff base. It can be easily reached at room temperature from the planar minima since it is separated from them by a barrier of only 0.6 kcal/mol. The 90 degrees minimum conformation is more stable than the all-trans by 8.6 kcal/mol. We are thus able to present a reaction path on the S(1) surface of the retinal Schiff base with an almost barrier-less geometrical relaxation into a twisted minimum geometry, as observed experimentally. The character of the ground and first excited singlet states underscores the need for the inclusion of double excitations in the calculations.
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Affiliation(s)
- A B Parusel
- NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035, USA.
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49
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Kobayashi T, Saito T, Ohtani H. Real-time spectroscopy of transition states in bacteriorhodopsin during retinal isomerization. Nature 2001; 414:531-4. [PMID: 11734850 DOI: 10.1038/35107042] [Citation(s) in RCA: 350] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Real-time investigations of the rearrangement of bonds during chemical transformations require femtosecond temporal resolution, so that the atomic vibrations within the reacting molecules can be observed. Following the development of lasers capable of emitting ultrashort laser flashes on this timescale, chemical reactions involving relatively simple molecules have been monitored in detail, revealing the transient existence of intermediate species as reactants are transformed into products. Here we report the direct observation of nuclear motion in a complex biological system, the retinal chromophore of bacteriorhodopsin (bR568), as it undergoes the trans-cis photoisomerization that is fundamental to the vision process. By using visible-light pulses of less than 5 femtosecond in duration, we are able to monitor changes in the vibrational spectra of the transition state and thus show that despite photoexcitation of the anti-bonding molecular orbital involved, isomerization does not occur instantly, but involves transient formation of a so-called 'tumbling state'. Our observations thus agree with growing experimental and ab initio evidence for a three-state photoisomerization model and firmly discount the initially suggested two-state model for this process.
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Affiliation(s)
- T Kobayashi
- Department of Physics, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan.
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50
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Logunov SL, Volkov VV, Braun M, El-Sayed MA. The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies. Proc Natl Acad Sci U S A 2001; 98:8475-9. [PMID: 11447258 PMCID: PMC37460 DOI: 10.1073/pnas.141220198] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present the results of two-pump and probe femtosecond experiments designed to follow the relaxation dynamics of the lowest excited state (S(1)) populated by different modes. In the first mode, a direct (S(0) --> S(1)) radiative excitation of the ground state is used. In the second mode, an indirect excitation is used where the S(1) state is populated by the use of two femtosecond laser pulses with different colors and delay times between them. The first pulse excites the S(0) --> S(1) transition whereas the second pulse excites the S(1) --> S(n) transition. The nonradiative relaxation from the S(n) state populates the lowest excited state. Our results suggest that the S(1) state relaxes faster when populated nonradiatively from the S(n) state than when pumped directly by the S(0) --> S(1) excitation. Additionally, the S(n) --> S(1) nonradiative relaxation time is found to change by varying the delay time between the two pump pulses. The observed dependence of the lowest excited state population as well as its dependence on the delay between the two pump pulses are found to fit a kinetic model in which the S(n) state populates a different surface (called S'(1)) than the one being directly excited (S(1)). The possible involvement of the A(g) type states, the J intermediate, and the conical intersection leading to the S(0) or to the isomerization product (K intermediate) are discussed in the framework of the proposed model.
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Affiliation(s)
- S L Logunov
- Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA
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