1
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Faries KM, Hanson DK, Buhrmaster JC, Hippleheuser S, Tira GA, Wyllie RM, Kohout CE, Magdaong NCM, Holten D, Laible PD, Kirmaier C. Two pathways to understanding electron transfer in reaction centers from photosynthetic bacteria: A comparison of Rhodobacter sphaeroides and Rhodobacter capsulatus mutants. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149047. [PMID: 38692451 DOI: 10.1016/j.bbabio.2024.149047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 04/23/2024] [Accepted: 04/24/2024] [Indexed: 05/03/2024]
Abstract
The rates, yields, mechanisms and directionality of electron transfer (ET) are explored in twelve pairs of Rhodobacter (R.) sphaeroides and R. capsulatus mutant RCs designed to defeat ET from the excited primary donor (P*) to the A-side cofactors and re-direct ET to the normally inactive mirror-image B-side cofactors. In general, the R. sphaeroides variants have larger P+HB- yields (up to ∼90%) than their R. capsulatus analogs (up to ∼60%), where HB is the B-side bacteriopheophytin. Substitution of Tyr for Phe at L-polypeptide position L181 near BB primarily increases the contribution of fast P* → P+BB- → P+HB- two-step ET, where BB is the "bridging" B-side bacteriochlorophyll. The second step (∼6-8 ps) is slower than the first (∼3-4 ps), unlike A-side two-step ET (P* → P+BA- → P+HA-) where the second step (∼1 ps) is faster than the first (∼3-4 ps) in the native RC. Substitutions near HB, at L185 (Leu, Trp or Arg) and at M-polypeptide site M133/131 (Thr, Val or Glu), strongly affect the contribution of slower (20-50 ps) P* → P+HB- one-step superexchange ET. Both ET mechanisms are effective in directing electrons "the wrong way" to HB and both compete with internal conversion of P* to the ground state (∼200 ps) and ET to the A-side cofactors. Collectively, the work demonstrates cooperative amino-acid control of rates, yields and mechanisms of ET in bacterial RCs and how A- vs. B-side charge separation can be tuned in both species.
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Affiliation(s)
- Kaitlyn M Faries
- Department of Chemistry, Washington University, St. Louis, MO 63130, United States of America
| | - Deborah K Hanson
- Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, United States of America
| | - James C Buhrmaster
- Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, United States of America
| | - Stephen Hippleheuser
- Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, United States of America
| | - Gregory A Tira
- Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, United States of America
| | - Ryan M Wyllie
- Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, United States of America
| | - Claire E Kohout
- Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, United States of America
| | - Nikki Cecil M Magdaong
- Department of Chemistry, Washington University, St. Louis, MO 63130, United States of America
| | - Dewey Holten
- Department of Chemistry, Washington University, St. Louis, MO 63130, United States of America
| | - Philip D Laible
- Biosciences Division, Argonne National Laboratory, Lemont, IL 60439, United States of America
| | - Christine Kirmaier
- Department of Chemistry, Washington University, St. Louis, MO 63130, United States of America.
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2
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Begam K, Aksu H, Dunietz BD. Antioxidative Triplet Excitation Energy Transfer in Bacterial Reaction Center Using a Screened Range Separated Hybrid Functional. J Phys Chem B 2024. [PMID: 38687467 DOI: 10.1021/acs.jpcb.3c08501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Excess energy absorbed by photosystems (PSs) can result in photoinduced oxidative damage. Transfer of such energy within the core pigments of the reaction center in the form of triplet excitation is important in regulating and preserving the functionality of PSs. In the bacterial reaction center (BRC), the special pair (P) is understood to act as the electron donor in a photoinduced charge transfer process, triggering the charge separation process through the photoactive branch A pigments that experience a higher polarizing environment. At this work, triplet excitation energy transfer (TEET) in BRC is studied using a computational perspective to gain insights into the roles of the dielectric environment and interpigment orientations. We find in agreement with experimental observations that TEET proceeds through branch B. The TEET process toward branch B pigment is found to be significantly faster than the hypothetical process proceeding through branch A pigments with ps and ms time scales, respectively. Our calculations find that conformational differences play a major role in this branch asymmetry in TEET, where the dielectric environment asymmetry plays only a secondary role in directing the TEET to proceed through branch B. We also address TEET processes asserting the role of carotenoid as the final triplet energy acceptor and in a mutant form, where the branch pigments adjacent to P are replaced by bacteriopheophytins. The necessary electronic excitation energies and electronic state couplings are calculated by the recently developed polarization-consistent framework combining a screened range-separated hybrid functional and a polarizable continuum mode. The polarization-consistent potential energy surfaces are used to parametrize the quantum mechanical approach, implementing Fermi's golden rule expression of the TEET rate calculations.
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Affiliation(s)
- Khadiza Begam
- Department of Physics, Kent State University, Kent, Ohio 44242, United States
| | - Huseyin Aksu
- Department of Physics, Faculty of Science at Canakkale Onsekiz Mart University, Canakkale 17100, Turkey
| | - Barry D Dunietz
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
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3
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Gemeinhardt FG, Lahav Y, Schapiro I, Noy D, Müh F, Lindorfer D, Renger T. Short-Range Effects in the Special Pair of Photosystem II Reaction Centers: The Nonconservative Nature of Circular Dichroism. J Phys Chem Lett 2023; 14:11758-11767. [PMID: 38117270 PMCID: PMC10758115 DOI: 10.1021/acs.jpclett.3c02693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/29/2023] [Accepted: 12/04/2023] [Indexed: 12/21/2023]
Abstract
Photosystem II reaction centers extract electrons from water, providing the basis of oxygenic life on earth. Among the light-sensitive pigments of the reaction center, a central chlorophyll a dimer, known as the special pair, so far has escaped a complete theoretical characterization of its excited state properties. The close proximity of the special pair pigments gives rise to short-range effects that comprise a coupling between local and charge transfer (CT) excited states as well as other intermolecular quantum effects. Using a multiscale simulation and a diabatization technique, we show that the coupling to CT states is responsible for 45% of the excitonic coupling in the special pair. The other short-range effects cause a nonconservative nature of the circular dichroism spectrum of the reaction center by effectively rotating the electric transition dipole moments of the special pair pigments inverting and strongly enhancing their intrinsic rotational strength.
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Affiliation(s)
- Felix G. Gemeinhardt
- Institut
für Theoretische Physik, Johannes
Kepler Universität Linz, Altenberger Strasse 69, 4040 Linz, Austria
| | - Yigal Lahav
- Fritz
Haber Center for Molecular Dynamics Research, Institute of Chemistry, Hebrew University of Jerusalem, 9190401 Jerusalem, Israel
- MIGAL
- Galilee Research Institute, S. Industrial Zone, 1101602 Kiryat Shmona, Israel
| | - Igor Schapiro
- Fritz
Haber Center for Molecular Dynamics Research, Institute of Chemistry, Hebrew University of Jerusalem, 9190401 Jerusalem, Israel
| | - Dror Noy
- MIGAL
- Galilee Research Institute, S. Industrial Zone, 1101602 Kiryat Shmona, Israel
- Faculty
of Sciences and Technology, Tel-Hai Academic
College, 1220800 Upper Galilee, Israel
| | - Frank Müh
- Institut
für Theoretische Physik, Johannes
Kepler Universität Linz, Altenberger Strasse 69, 4040 Linz, Austria
| | - Dominik Lindorfer
- Institut
für Theoretische Physik, Johannes
Kepler Universität Linz, Altenberger Strasse 69, 4040 Linz, Austria
| | - Thomas Renger
- Institut
für Theoretische Physik, Johannes
Kepler Universität Linz, Altenberger Strasse 69, 4040 Linz, Austria
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4
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Bradley JM, Coleman AF, Brown PJ, Huang Y, Young RM, Wasielewski MR. Harvesting electrons and holes from photodriven symmetry-breaking charge separation within a perylenediimide photosynthetic model dimer. Proc Natl Acad Sci U S A 2023; 120:e2313575120. [PMID: 37983509 PMCID: PMC10691211 DOI: 10.1073/pnas.2313575120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 10/11/2023] [Indexed: 11/22/2023] Open
Abstract
Understanding how to utilize symmetry-breaking charge separation (SB-CS) offers a path toward increasingly efficient light-harvesting technologies. This process plays a central role in the first step of photosynthesis, in which the dimeric "special pair" of the photosynthetic reaction center enters a coherent SB-CS state after photoexcitation. Previous research on SB-CS in both biological and synthetic chromophore dimers has focused on increasing the efficiency of light-driven processes. In a chromophore dimer undergoing SB-CS, the energy of the radical ion pair product is nearly isoenergetic with that of the lowest excited singlet (S1) state of the dimer. This means that very little energy is lost from the absorbed photon. In principle, the relatively high energy electron and hole generated by SB-CS within the chromophore dimer can each be transferred to adjacent charge acceptors to extend the lifetime of the electron-hole pair, which can increase the efficiency of solar energy conversion. To investigate this possibility, we have designed a bis-perylenediimide cyclophane (mPDI2) covalently linked to a secondary electron donor, peri-xanthenoxanthene (PXX) and a secondary electron acceptor, partially fluorinated naphthalenediimide (FNDI). Upon selective photoexcitation of mPDI2, transient absorption spectroscopy shows that mPDI2 undergoes SB-CS, followed by two secondary charge transfer reactions to generate a PXX•+-mPDI2-FNDI•- radical ion pair having a nearly 3 µs lifetime. This strategy has the potential to increase the efficiency of molecular systems for artificial photosynthesis and photovoltaics.
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Affiliation(s)
- Jillian M. Bradley
- Department of Chemistry, Northwestern University, Evanston, IL60208-3113
- Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL60208-3113
| | - Adam F. Coleman
- Department of Chemistry, Northwestern University, Evanston, IL60208-3113
- Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL60208-3113
| | - Paige J. Brown
- Department of Chemistry, Northwestern University, Evanston, IL60208-3113
- Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL60208-3113
| | - Yuheng Huang
- Department of Chemistry, Northwestern University, Evanston, IL60208-3113
- Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL60208-3113
| | - Ryan M. Young
- Department of Chemistry, Northwestern University, Evanston, IL60208-3113
- Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL60208-3113
| | - Michael R. Wasielewski
- Department of Chemistry, Northwestern University, Evanston, IL60208-3113
- Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL60208-3113
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5
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Nguyen HH, Song Y, Maret EL, Silori Y, Willow R, Yocum CF, Ogilvie JP. Charge separation in the photosystem II reaction center resolved by multispectral two-dimensional electronic spectroscopy. SCIENCE ADVANCES 2023; 9:eade7190. [PMID: 37134172 PMCID: PMC10156117 DOI: 10.1126/sciadv.ade7190] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The photosystem II reaction center (PSII RC) performs the primary energy conversion steps of oxygenic photosynthesis. While the PSII RC has been studied extensively, the similar time scales of energy transfer and charge separation and the severely overlapping pigment transitions in the Qy region have led to multiple models of its charge separation mechanism and excitonic structure. Here, we combine two-dimensional electronic spectroscopy (2DES) with a continuum probe and two-dimensional electronic vibrational spectroscopy (2DEV) to study the cyt b559-D1D2 PSII RC at 77 K. This multispectral combination correlates the overlapping Qy excitons with distinct anion and pigment-specific Qx and mid-infrared transitions to resolve the charge separation mechanism and excitonic structure. Through extensive simultaneous analysis of the multispectral 2D data, we find that charge separation proceeds on multiple time scales from a delocalized excited state via a single pathway in which PheoD1 is the primary electron acceptor, while ChlD1 and PD1 act in concert as the primary electron donor.
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Affiliation(s)
- Hoang H Nguyen
- Department of Physics and Biophysics, University of Michigan, 450 Church St., Ann Arbor, MI 48109, USA
| | - Yin Song
- Department of Physics and Biophysics, University of Michigan, 450 Church St., Ann Arbor, MI 48109, USA
- School of Optics and Photonics, Beijing Institute of Technology, 5 Zhongguancun South Street, Haidian District, Beijing, 100081, China
| | - Elizabeth L Maret
- Department of Physics and Biophysics, University of Michigan, 450 Church St., Ann Arbor, MI 48109, USA
| | - Yogita Silori
- Department of Physics and Biophysics, University of Michigan, 450 Church St., Ann Arbor, MI 48109, USA
| | - Rhiannon Willow
- Department of Physics and Biophysics, University of Michigan, 450 Church St., Ann Arbor, MI 48109, USA
| | - Charles F Yocum
- Department of Molecular, Cellular and Developmental Biology and Department of Chemistry, University of Michigan, 450 Church St, Ann Arbor, MI 48109, USA
| | - Jennifer P Ogilvie
- Department of Physics and Biophysics, University of Michigan, 450 Church St., Ann Arbor, MI 48109, USA
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6
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Zabelin AA, Khristin AM, Kovalev VB, Khatypov RA, Shkuropatov AY. Primary charge separation in native and plant pheophytin a-modified reaction centers of Chloroflexus aurantiacus: Ultrafast transient absorption measurements at low temperature. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148976. [PMID: 37061174 DOI: 10.1016/j.bbabio.2023.148976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/31/2023] [Accepted: 04/06/2023] [Indexed: 04/17/2023]
Abstract
Ultrafast transient absorption (TA) spectroscopy was used to study electron transfer (ET) at 100 K in native (as isolated) reaction centers (RCs) of the green filamentous photosynthetic bacterium Chloroflexus (Cfl.) aurantiacus. The rise and decay of the 1028 nm anion absorption band of the monomeric bacteriochlorophyll a molecule at the BA binding site were monitored as indicators of the formation and decay of the P+BA- state, respectively (P is the primary electron donor, a dimer of bacteriochlorophyll a molecules). Global analysis of the TA data indicated the presence of at least two populations of the P⁎ excited state, which decay by distinct means, forming the state P+HA- (HA is a photochemically active bacteriopheophytin a molecule). In one population (~65 %), P⁎ decays in ~2 ps with the formation of P+HA- via a short-lived P+BA- intermediate in a two-step ET process P⁎ → P+BA- → P+HA-. In another population (~35 %), P⁎ decays in ~20 ps to form P+HA- via a superexchange mechanism without producing measurable amounts of P+BA-. Similar TA measurements performed on chemically modified RCs of Cfl. aurantiacus containing plant pheophytin a at the HA binding site also showed the presence of two P⁎ populations (~2 and ~20 ps), with P⁎ decaying through P+BA- only in the ~2 ps population. At 100 K, the quantum yield of primary charge separation in native RCs is determined to be close to unity. The results are discussed in terms of involving a one-step P⁎ → P+HA- superexchange process as an alternative highly efficient ET pathway in Cfl. aurantiacus RCs.
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Affiliation(s)
- Alexey A Zabelin
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Anton M Khristin
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Vyacheslav B Kovalev
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Ravil A Khatypov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Anatoly Yu Shkuropatov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation.
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7
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Brütting M, Foerster JM, Kümmel S. Understanding Primary Charge Separation in the Heliobacterial Reaction Center. J Phys Chem Lett 2023; 14:3092-3102. [PMID: 36951395 DOI: 10.1021/acs.jpclett.3c00377] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The homodimeric reaction center of heliobacteria retains features of the ancestral reaction center and can thus provide insights into the evolution of photosynthesis. Primary charge separation is expected to proceed in a two-step mechanism along either of the two reaction center branches. We reveal the first charge-separation step from first-principles calculations based on time-dependent density functional theory with an optimally tuned range-separated hybrid and ab initio Born-Oppenheimer molecular dynamics: the electron is most likely localized on the electron transfer cofactor 3 (EC3, OH-chlorophyll a), and the hole on the adjacent EC2. Including substantial parts of the surrounding protein environment into the calculations shows that a distinct structural mechanism is decisive for the relative energetic positioning of the electronic excitations: specific charged amino acids in the vicinity of EC3 lower the energy of charge-transfer excitations and thus facilitate efficient charge separation. These results are discussed considering recent experimental insights.
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8
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Magdaong NCM, Faries KM, Buhrmaster JC, Tira GA, Wyllie RM, Kohout CE, Hanson DK, Laible PD, Holten D, Kirmaier C. High Yield of B-Side Electron Transfer at 77 K in the Photosynthetic Reaction Center Protein from Rhodobacter sphaeroides. J Phys Chem B 2022; 126:8940-8956. [PMID: 36315401 DOI: 10.1021/acs.jpcb.2c05905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The primary electron transfer (ET) processes at 295 and 77 K are compared for the Rhodobacter sphaeroides reaction center (RC) pigment-protein complex from 13 mutants including a wild-type control. The engineered RCs bear mutations in the L and M polypeptides that largely inhibit ET from the excited state P* of the primary electron donor (P, a bacteriochlorophyll dimer) to the normally photoactive A-side cofactors and enhance ET to the C2-symmetry related, and normally photoinactive, B-side cofactors. P* decay is multiexponential at both temperatures and modeled as arising from subpopulations that differ in contributions of two-step ET (e.g., P* → P+BB- → P+HB-), one-step superexchange ET (e.g., P* → P+HB-), and P* → ground state. [HB and BB are monomeric bacteriopheophytin and bacteriochlorophyll, respectively.] The relative abundances of the subpopulations and the inherent rate constants of the P* decay routes vary with temperature. Regardless, ET to produce P+HB- is generally faster at 77 K than at 295 K by about a factor of 2. A key finding is that the yield of P+HB-, which ranges from ∼5% to ∼90% among the mutant RCs, is essentially the same at 77 K as at 295 K in each case. Overall, the results show that ET from P* to the B-side cofactors in these mutants does not require thermal activation and involves combinations of ET mechanisms analogous to those operative on the A side in the native RC.
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Affiliation(s)
- Nikki Cecil M Magdaong
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Kaitlyn M Faries
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - James C Buhrmaster
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Gregory A Tira
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Ryan M Wyllie
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Claire E Kohout
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Deborah K Hanson
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Philip D Laible
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Dewey Holten
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Christine Kirmaier
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
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9
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Tale Moghim M, Jamehbozorgi S, Rezvani M, Ramezani M. Computational investigation on the geometry and electronic structures and absorption spectra of metal-porphyrin-oligo- phenyleneethynylenes-[60] fullerene triads. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 280:121488. [PMID: 35759932 DOI: 10.1016/j.saa.2022.121488] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 06/02/2022] [Accepted: 06/06/2022] [Indexed: 06/15/2023]
Abstract
In this work, we focus our attention on the influence of 2nd-row transition metals on the structural geometries, electronic structures, and absorption characteristics of porphyrin linked with the C60 fullerene with oligo-p-phenyleneethynylenes (MP-C60-oligo-PPEs) compounds. The DFT/B3PW91-D3 and CAM-B3LYP-D3/6-31G (d) calculations revealed that various metals embedded within the porphyrin moiety give different bridge conformations and different HOMO-LUMO energy levels. We calculate the UV-Vis spectra and absorption parameters using the time-dependent ZINDO/S approach. Our findings indicate that all the compounds have enhanced absorptions in the visible light range, and their molecular orbital energies adopt the condition of sensitizers. However, all of the complexes except down spin states exhibit considerably charge spatial separation. The results suggest that the ZnP-C60-oligo-PPEs triad can meet the necessary conditions of the sensitizer of dye-sensitized solar cells (DSSCs) in comparison with other counterparts and could be an optimum triad compound for potential application in photovoltaic devices.
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Affiliation(s)
- Masoud Tale Moghim
- Department of Chemistry, Faculty of Science Arak Branch, Islamic Azad University, Arak, Iran
| | - Saeed Jamehbozorgi
- Department of Chemistry, Faculty of Science Hamedan Branch, Islamic Azad University, Hamedan, Iran.
| | - Mahyar Rezvani
- Department of Chemistry, Faculty of Science Hamedan Branch, Islamic Azad University, Hamedan, Iran.
| | - Majid Ramezani
- Department of Chemistry, Faculty of Science Hamedan Branch, Islamic Azad University, Hamedan, Iran
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10
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Zabelin AA, Kovalev VB, Shkuropatov AY. On the Mechanism of Selective Chemical Exchange of Bacteriopheophytins in the Reaction Centers of Rhodobacter sphaeroides R-26. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:1119-1129. [PMID: 36273880 DOI: 10.1134/s0006297922100054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/11/2022] [Accepted: 08/10/2022] [Indexed: 06/16/2023]
Abstract
To elucidate the mechanism of site-selective chemical replacement of chromophores in the reaction centers (RCs) of photosynthetic bacteria by external pigments, we investigated how the efficiency of incorporation of plant pheophytin a (Pheo) into the binding sites for bacteriopheophytin a molecules (BPheo) in the isolated Rhodobacter sphaeroides R-26 RCs depended on the incubation medium temperature, Pheo aggregation state, and the presence of organic solvent (acetone). When Pheo was in a form of monomers in free detergent micelles in a water-detergent incubation medium, the degree of selective replacement of photochemically inactive BPheo HB molecules upon incubation of the RC/Pheo mixture at 5°C was ~15%. The exchange efficiency increased to 40% upon incubation at 25°C and reached 100% at the same temperature when 10% acetone was added to the incubation medium. At both 5 and 25°C, the degree of pigment exchange increased approximately twice, when a mixture of Pheo monomers and dimers in the presence of 10% acetone was used as the incubation medium. The removal of acetone from this medium with the preservation of pigment forms led to a significant decrease in the efficiency of Pheo incorporation. The effect of acetone on the pigment exchange was also observed at an elevated incubation temperature (43.5°C), when functionally active BPheo HA molecules were partially replaced. The results are discussed in terms of the mechanism according to which (i) the temperature-dependent internal movements of the RC protein facilitate the release of the BPheo molecule from the binding site with simultaneous insertion of the Pheo molecule into the same site in a coupled process, (ii) the role of temperature largely depends on the steric accessibility of binding pockets in the RC protein, (iii) the incorporation of Pheo occurs from a pool of monomeric molecules included in the RC-detergent micelles, and (iv) the presence of acetone in the incubation medium facilitates the exchange of Pheo monomers between micelles in the solution and the detergent belt of the RC complex.
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Affiliation(s)
- Alexey A Zabelin
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
| | - Vyacheslav B Kovalev
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Anatoly Ya Shkuropatov
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
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11
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Wang C, O'Hagan MP, Li Z, Zhang J, Ma X, Tian H, Willner I. Photoresponsive DNA materials and their applications. Chem Soc Rev 2022; 51:720-760. [PMID: 34985085 DOI: 10.1039/d1cs00688f] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Photoresponsive nucleic acids attract growing interest as functional constituents in materials science. Integration of photoisomerizable units into DNA strands provides an ideal handle for the reversible reconfiguration of nucleic acid architectures by light irradiation, triggering changes in the chemical and structural properties of the nanostructures that can be exploited in the development of photoresponsive functional devices such as machines, origami structures and ion channels, as well as environmentally adaptable 'smart' materials including nanoparticle aggregates and hydrogels. Moreover, photoresponsive DNA components allow control over the composition of dynamic supramolecular ensembles that mimic native networks. Beyond this, the modification of nucleic acids with photosensitizer functionality enables these biopolymers to act as scaffolds for spatial organization of electron transfer reactions mimicking natural photosynthesis. This review provides a comprehensive overview of these exciting developments in the design of photoresponsive DNA materials, and showcases a range of applications in catalysis, sensing and drug delivery/release. The key challenges facing the development of the field in the coming years are addressed, and exciting emergent research directions are identified.
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Affiliation(s)
- Chen Wang
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | - Michael P O'Hagan
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | - Ziyuan Li
- Key Laboratory for Advanced Materials, Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, School of Chemistry and Molecular Engineering, Frontiers Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai 200237, P. R. China
| | - Junji Zhang
- Key Laboratory for Advanced Materials, Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, School of Chemistry and Molecular Engineering, Frontiers Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai 200237, P. R. China
| | - Xiang Ma
- Key Laboratory for Advanced Materials, Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, School of Chemistry and Molecular Engineering, Frontiers Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai 200237, P. R. China
| | - He Tian
- Key Laboratory for Advanced Materials, Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, School of Chemistry and Molecular Engineering, Frontiers Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai 200237, P. R. China
| | - Itamar Willner
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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12
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Photosynthetic reaction center variants made via genetic code expansion show Tyr at M210 tunes the initial electron transfer mechanism. Proc Natl Acad Sci U S A 2021; 118:2116439118. [PMID: 34907018 DOI: 10.1073/pnas.2116439118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2021] [Indexed: 11/18/2022] Open
Abstract
Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine (M210) close to an essential electron transfer component via its replacement with site-specific, genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and X-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild type (WT). Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via a ∼4-ps and a ∼20-ps population to produce the charge-separated state P+HA - in all variants. Global analysis indicates that in the ∼4-ps population, P+HA - forms through a two-step process, P*→ P+BA -→ P+HA -, while in the ∼20-ps population, it forms via a one-step P* → P+HA - superexchange mechanism. The percentage of the P* population that decays via the superexchange route varies from ∼25 to ∼45% among variants, while in WT, this percentage is ∼15%. Increases in the P* population that decays via superexchange correlate with increases in the free energy of the P+BA - intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an ∼110-meV increase in the free energy of P+BA - along with a dramatic diminution of the 1,030-nm transient absorption band indicative of P+BA - formation. Collectively, this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.
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13
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Stiel H, Braenzel J, Jonas A, Gnewkow R, Glöggler LT, Sommer D, Krist T, Erko A, Tümmler J, Mantouvalou I. Towards Understanding Excited-State Properties of Organic Molecules Using Time-Resolved Soft X-ray Absorption Spectroscopy. Int J Mol Sci 2021; 22:13463. [PMID: 34948258 PMCID: PMC8706469 DOI: 10.3390/ijms222413463] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/01/2021] [Accepted: 12/08/2021] [Indexed: 11/16/2022] Open
Abstract
The extension of the pump-probe approach known from UV/VIS spectroscopy to very short wavelengths together with advanced simulation techniques allows a detailed analysis of excited-state dynamics in organic molecules or biomolecular structures on a nanosecond to femtosecond time level. Optical pump soft X-ray probe spectroscopy is a relatively new approach to detect and characterize optically dark states in organic molecules, exciton dynamics or transient ligand-to-metal charge transfer states. In this paper, we describe two experimental setups for transient soft X-ray absorption spectroscopy based on an LPP emitting picosecond and sub-nanosecond soft X-ray pulses in the photon energy range between 50 and 1500 eV. We apply these setups for near-edge X-ray absorption fine structure (NEXAFS) investigations of thin films of a metal-free porphyrin, an aggregate forming carbocyanine and a nickel oxide molecule. NEXAFS investigations have been carried out at the carbon, nitrogen and oxygen K-edge as well as on the Ni L-edge. From time-resolved NEXAFS carbon, K-edge measurements of the metal-free porphyrin first insights into a long-lived trap state are gained. Our findings are discussed and compared with density functional theory calculations.
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Affiliation(s)
- Holger Stiel
- Berlin Laboratory for Innovative X-ray Technologies (BLiX), D-10623 Berlin, Germany; (J.B.); (A.J.); (R.G.); (L.T.G.); (J.T.); (I.M.)
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany;
| | - Julia Braenzel
- Berlin Laboratory for Innovative X-ray Technologies (BLiX), D-10623 Berlin, Germany; (J.B.); (A.J.); (R.G.); (L.T.G.); (J.T.); (I.M.)
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany;
| | - Adrian Jonas
- Berlin Laboratory for Innovative X-ray Technologies (BLiX), D-10623 Berlin, Germany; (J.B.); (A.J.); (R.G.); (L.T.G.); (J.T.); (I.M.)
- Analytical X-ray Physics, TU Berlin, D-10623 Berlin, Germany
| | - Richard Gnewkow
- Berlin Laboratory for Innovative X-ray Technologies (BLiX), D-10623 Berlin, Germany; (J.B.); (A.J.); (R.G.); (L.T.G.); (J.T.); (I.M.)
- Analytical X-ray Physics, TU Berlin, D-10623 Berlin, Germany
- Helmholtz Zentrum Berlin, D-12489 Berlin, Germany
| | - Lisa Theresa Glöggler
- Berlin Laboratory for Innovative X-ray Technologies (BLiX), D-10623 Berlin, Germany; (J.B.); (A.J.); (R.G.); (L.T.G.); (J.T.); (I.M.)
- Analytical X-ray Physics, TU Berlin, D-10623 Berlin, Germany
| | - Denny Sommer
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany;
| | - Thomas Krist
- NOB Nano Optics Berlin GmbH, D-10627 Berlin, Germany;
| | | | - Johannes Tümmler
- Berlin Laboratory for Innovative X-ray Technologies (BLiX), D-10623 Berlin, Germany; (J.B.); (A.J.); (R.G.); (L.T.G.); (J.T.); (I.M.)
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany;
| | - Ioanna Mantouvalou
- Berlin Laboratory for Innovative X-ray Technologies (BLiX), D-10623 Berlin, Germany; (J.B.); (A.J.); (R.G.); (L.T.G.); (J.T.); (I.M.)
- Analytical X-ray Physics, TU Berlin, D-10623 Berlin, Germany
- Helmholtz Zentrum Berlin, D-12489 Berlin, Germany
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14
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Bozovic O, Jankovic B, Hamm P. Using azobenzene photocontrol to set proteins in motion. Nat Rev Chem 2021; 6:112-124. [PMID: 37117294 DOI: 10.1038/s41570-021-00338-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2021] [Indexed: 02/06/2023]
Abstract
Controlling the activity of proteins with azobenzene photoswitches is a potent tool for manipulating their biological function. With the help of light, it is possible to change binding affinities, control allostery or manipulate complex biological processes, for example. Additionally, owing to their intrinsically fast photoisomerization, azobenzene photoswitches can serve as triggers that initiate out-of-equilibrium processes. Such switching of the activity initiates a cascade of conformational events that can be accessed with time-resolved methods. In this Review, we show how the potency of azobenzene photoswitching can be combined with transient spectroscopic techniques to disclose the order of events and experimentally observe biomolecular interactions in real time. This strategy will further our understanding of how a protein can accommodate, adapt and readjust its structure to answer an incoming signal, revealing more of the dynamical character of proteins.
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15
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Wang C, O'Hagan MP, Willner B, Willner I. Bioinspired Artificial Photosynthetic Systems. Chemistry 2021; 28:e202103595. [PMID: 34854505 DOI: 10.1002/chem.202103595] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Indexed: 12/18/2022]
Abstract
Mimicking photosynthesis using artificial systems, as a means for solar energy conversion and green fuel generation, is one of the holy grails of modern science. This perspective presents recent advances towards developing artificial photosynthetic systems. In one approach, native photosystems are interfaced with electrodes to yield photobioelectrochemical cells that transform light energy into electrical power. This is exemplified by interfacing photosystem I (PSI) and photosystem II (PSII) as an electrically contacted assembly mimicking the native Z-scheme, and by the assembly of an electrically wired PSI/glucose oxidase biocatalytic conjugate on an electrode support. Illumination of the functionalized electrodes led to light-induced generation of electrical power, or to the generation of photocurrents using glucose as the fuel. The second approach introduces supramolecular photosensitizer nucleic acid/electron acceptor complexes as functional modules for effective photoinduced electron transfer stimulating the subsequent biocatalyzed generation of NADPH or the Pt-nanoparticle-catalyzed evolution of molecular hydrogen. Application of the DNA machineries for scaling-up the photosystems is demonstrated. A third approach presents the integration of artificial photosynthetic modules into dynamic nucleic acid networks undergoing reversible reconfiguration or dissipative transient operation in the presence of auxiliary triggers. Control over photoinduced electron transfer reactions and photosynthetic transformations by means of the dynamic networks is demonstrated.
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Affiliation(s)
- Chen Wang
- Institute of Chemistry, The Minerva Centre for Bio-Hybrid Complex Systems, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Michael P O'Hagan
- Institute of Chemistry, The Minerva Centre for Bio-Hybrid Complex Systems, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Bilha Willner
- Institute of Chemistry, The Minerva Centre for Bio-Hybrid Complex Systems, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Itamar Willner
- Institute of Chemistry, The Minerva Centre for Bio-Hybrid Complex Systems, The Hebrew University of Jerusalem, Jerusalem, Israel
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16
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Zabelin AA, Shkuropatov AY. Pigment-modified reaction centers of Chloroflexus aurantiacus: chemical exchange of bacteriopheophytins with plant-type pheophytins. PHOTOSYNTHESIS RESEARCH 2021; 149:313-328. [PMID: 34138452 DOI: 10.1007/s11120-021-00855-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 06/06/2021] [Indexed: 06/12/2023]
Abstract
The pigment composition of isolated reaction centers (RCs) of the green filamentous bacterium Chloroflexus (Cfl.) aurantiacus was changed by chemical exchange of native bacteriopheophytin a (BPheo) molecules with externally added pheophytin a (Pheo) or [3-acetyl]-Pheo upon incubation of RC/pheophytin mixtures at room temperature and 45 °C. The modified RCs were characterized by Vis/NIR absorption spectroscopy, and the effect of pigment exchange on RC photochemical activity was assessed by measuring the photoaccumulation of the reduced pigment at the binding site HA. It is shown that both pheophytins can be exchanged into the HA site instead of BPheo by incubation at room temperature. While the newly introduced Pheo molecule is not active in electron transfer, the [3-acetyl]-Pheo molecule is able to replace functionally the photoreducible HA BPheo molecule with the formation of the [3-acetyl]-Pheo- radical anion instead of the BPheo-. After incubation at 45 °C, the majority (~ 90%) of HA BPheo molecules is replaced by both Pheo and [3-acetyl]-Pheo. Only a partial replacement of inactive BPheo molecules with pheophytins is observed even when the incubation temperature is raised to 50 °C. The results are discussed in terms of (i) differences in the accessibility of BPheo binding sites for extraneous pigments depending on structural constraints and incubation temperature and (ii) the effect of the reduction potential of pigments introduced into the HA site on the energetics of the charge separation process. The possible implication of Pheo-exchanged preparations for studying early electron-transfer events in Cfl. aurantiacus RCs is considered.
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Affiliation(s)
- Alexey A Zabelin
- Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Institute of Basic Biological Problems of the Russian Academy of Sciences, 142290, Pushchino, Moscow Region, Russian Federation
| | - Anatoly Ya Shkuropatov
- Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Institute of Basic Biological Problems of the Russian Academy of Sciences, 142290, Pushchino, Moscow Region, Russian Federation.
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17
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Bubilaitis V, Rancova O, Abramavicius D. Vibration-mediated energy transport in bacterial reaction center: Simulation study. J Chem Phys 2021; 154:214115. [PMID: 34240965 DOI: 10.1063/5.0048815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exciton energy relaxation in a bacterial Reaction Center (bRC) pigment-protein aggregate presumably involves emission of high energy vibrational quanta to cover wide energy gaps between excitons. Here, we assess this hypothesis utilizing vibronic two-particle theory in modeling of the excitation relaxation process in bRC. Specific high frequency molecular vibrational modes are included explicitly one at a time in order to check which high frequency vibrations are involved in the excitation relaxation process. The low frequency bath modes are treated perturbatively within Redfield relaxation theory. The analysis of the population relaxation rate data indicates energy flow pathways in bRC and suggests that specific vibrations may be responsible for the excitation relaxation process.
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Affiliation(s)
- Vytautas Bubilaitis
- Institute of Chemical Physics, Vilnius University, Sauletekio al. 9-III, Vilnius 10222, Lithuania
| | - Olga Rancova
- Institute of Chemical Physics, Vilnius University, Sauletekio al. 9-III, Vilnius 10222, Lithuania
| | - Darius Abramavicius
- Institute of Chemical Physics, Vilnius University, Sauletekio al. 9-III, Vilnius 10222, Lithuania
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18
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Dubas K, Szewczyk S, Białek R, Burdziński G, Jones MR, Gibasiewicz K. Antagonistic Effects of Point Mutations on Charge Recombination and a New View of Primary Charge Separation in Photosynthetic Proteins. J Phys Chem B 2021; 125:8742-8756. [PMID: 34328746 PMCID: PMC8389993 DOI: 10.1021/acs.jpcb.1c03978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Light-induced electron-transfer
reactions were investigated in
wild-type and three mutant Rhodobacter sphaeroides reaction centers with the secondary electron acceptor (ubiquinone
QA) either removed or permanently reduced. Under such conditions,
charge separation between the primary electron donor (bacteriochlorophyll
dimer, P) and the electron acceptor (bacteriopheophytin, HA) was followed by P+HA– →
PHA charge recombination. Two reaction centers were used
that had different single amino-acid mutations that brought about
either a 3-fold acceleration in charge recombination compared to that
in the wild-type protein, or a 3-fold deceleration. In a third mutant
in which the two single amino-acid mutations were combined, charge
recombination was similar to that in the wild type. In all cases,
data from transient absorption measurements were analyzed using similar
models. The modeling included the energetic relaxation of the charge-separated
states caused by protein dynamics and evidenced the appearance of
an intermediate charge-separated state, P+BA–, with BA being the bacteriochlorophyll
located between P and HA. In all cases, mixing of the states
P+BA– and P+HA– was observed and explained in terms of
electron delocalization over BA and HA. This
delocalization, together with picosecond protein relaxation, underlies
a new view of primary charge separation in photosynthesis.
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Affiliation(s)
- K Dubas
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznanskiego 2, 61-614 Poznań, Poland.,Department of Optometry, Poznan University of Medical Sciences, ul. Rokietnicka 5d, 60-806 Poznań, Poland
| | - S Szewczyk
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznanskiego 2, 61-614 Poznań, Poland
| | - R Białek
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznanskiego 2, 61-614 Poznań, Poland
| | - G Burdziński
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznanskiego 2, 61-614 Poznań, Poland
| | - M R Jones
- School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, U.K
| | - K Gibasiewicz
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznanskiego 2, 61-614 Poznań, Poland
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19
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Gibasiewicz K, Pajzderska M, Białek R, Jones MR. Temperature dependence of nanosecond charge recombination in mutant Rhodobacter sphaeroides reaction centers: modelling of the protein dynamics. Photochem Photobiol Sci 2021; 20:913-922. [PMID: 34213754 DOI: 10.1007/s43630-021-00069-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 06/18/2021] [Indexed: 10/20/2022]
Abstract
We investigated the influence of a range of factors-temperature, redox midpoint potential of an electron carrier, and protein dynamics-on nanosecond electron transfer within a protein. The model reaction was back electron transfer from a bacteriopheophytin anion, HA-, to an oxidized primary electron donor, P+, in a wild type Rhodobacter sphaeroides reaction center (RC) with a permanently reduced secondary electron acceptor (quinone, QA-). Also used were two modified RCs with single amino acid mutations near the monomeric bacteriochlorophyll, BA, located between P and HA. Both mutant RCs showed significant slowing down of this back electron transfer reaction with decreasing temperature, similar to that observed with the wild type RC, but contrasting with a number of single point mutant RCs studied previously. The observed similarities and differences are explained in the framework of a (P+BA- ↔ P+HA-) equilibrium model with an important role played by protein relaxation. The major cause of the observed temperature dependence, both in the wild type RC and in the mutant proteins, is a limitation in access to the thermally activated pathway of charge recombination via the state P+BA- at low temperatures. The data indicate that in all RCs both charge recombination pathways, the thermally activated one and a direct one without involvement of the P+BA- state, are controlled by the protein dynamics. It is concluded that the modifications of the protein environment affect the overall back electron transfer kinetics primarily by changing the redox potential of BA and not by changing the protein relaxation dynamics.
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Affiliation(s)
- Krzysztof Gibasiewicz
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland.
| | - Maria Pajzderska
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland
| | - Rafał Białek
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Medical Sciences BuildingUniversity Walk, Bristol, BS8 1TD, UK
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20
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Ma F, Romero E, Jones MR, Novoderezhkin VI, Yu LJ, van Grondelle R. Dynamic Stark Effect in Two-Dimensional Spectroscopy Revealing Modulation of Ultrafast Charge Separation in Bacterial Reaction Centers by an Inherent Electric Field. J Phys Chem Lett 2021; 12:5526-5533. [PMID: 34096727 DOI: 10.1021/acs.jpclett.1c01059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Despite extensive study, mysteries remain regarding the highly efficient ultrafast charge separation processes in photosynthetic reaction centers (RCs). In this work, transient Stark signals were found to be present in ultrafast two-dimensional electronic spectra recorded for purple bacterial RCs at 77 K. These arose from the electric field that is inherent to the intradimer charge-transfer intermediate of the bacteriochlorophyll pair (P), PA+PB-. By comparing three mutated RCs, a correlation was found between the efficient formation of PA+PB- and a fast charge separation rate. Importantly, the energy level of P* was changed due to the Stark shift, influencing the driving force for P* → P+BA- electron transfer and hence its rate. Furthermore, the orientation and amplitude of the inherent electric field varied in different ways upon different mutation, leading to contrasting changes in the rates. This mechanism of modulation provides a solution to a long-lasting inconsistency between experimental observations and activation energy theory.
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Affiliation(s)
- Fei Ma
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing 100093, China
- Department of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Elisabet Romero
- Department of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, U.K
| | - Vladimir I Novoderezhkin
- A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Leninskie Gory, 119992 Moscow, Russia
| | - Long-Jiang Yu
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing 100093, China
| | - Rienk van Grondelle
- Department of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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21
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Amoruso G, Liu J, Polak DW, Tiwari K, Jones MR, Oliver TAA. High-Efficiency Excitation Energy Transfer in Biohybrid Quantum Dot-Bacterial Reaction Center Nanoconjugates. J Phys Chem Lett 2021; 12:5448-5455. [PMID: 34081477 DOI: 10.1021/acs.jpclett.1c01407] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Reaction centers (RCs) are the pivotal component of natural photosystems, converting solar energy into the potential difference between separated electrons and holes that is used to power much of biology. RCs from anoxygenic purple photosynthetic bacteria such as Rhodobacter sphaeroides only weakly absorb much of the visible region of the solar spectrum, which limits their overall light-harvesting capacity. For in vitro applications such as biohybrid photodevices, this deficiency can be addressed by effectively coupling RCs with synthetic light-harvesting materials. Here, we studied the time scale and efficiency of Förster resonance energy transfer (FRET) in a nanoconjugate assembled from a synthetic quantum dot (QD) antenna and a tailored RC engineered to be fluorescent. Time-correlated single-photon counting spectroscopy of biohybrid conjugates enabled the direct determination of FRET from QDs to attached RCs on a time scale of 26.6 ± 0.1 ns and with a high efficiency of 0.75 ± 0.01.
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Affiliation(s)
- Giordano Amoruso
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Juntai Liu
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Daniel W Polak
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
| | - Kavita Tiwari
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, U.K
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, U.K
| | - Thomas A A Oliver
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K
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22
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Excitonic structure and charge separation in the heliobacterial reaction center probed by multispectral multidimensional spectroscopy. Nat Commun 2021; 12:2801. [PMID: 33990569 PMCID: PMC8121816 DOI: 10.1038/s41467-021-23060-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 04/09/2021] [Indexed: 12/29/2022] Open
Abstract
Photochemical reaction centers are the engines that drive photosynthesis. The reaction center from heliobacteria (HbRC) has been proposed to most closely resemble the common ancestor of photosynthetic reaction centers, motivating a detailed understanding of its structure-function relationship. The recent elucidation of the HbRC crystal structure motivates advanced spectroscopic studies of its excitonic structure and charge separation mechanism. We perform multispectral two-dimensional electronic spectroscopy of the HbRC and corresponding numerical simulations, resolving the electronic structure and testing and refining recent excitonic models. Through extensive examination of the kinetic data by lifetime density analysis and global target analysis, we reveal that charge separation proceeds via a single pathway in which the distinct A0 chlorophyll a pigment is the primary electron acceptor. In addition, we find strong delocalization of the charge separation intermediate. Our findings have general implications for the understanding of photosynthetic charge separation mechanisms, and how they might be tuned to achieve different functional goals. The primary energy conversion step in photosynthesis, charge separation, takes place in the reaction center. Here the authors investigate the heliobacterial reaction center using multispectral two-dimensional electronic spectroscopy, identifying the primary electron acceptor and revealing the charge separation mechanism.
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23
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Aksu H, Maiti B, Ptaszek M, Dunietz BD. Photoinduced charge transfer in Zn(II) and Au(III)-ligated symmetric and asymmetric bacteriochlorin dyads: A computational study. J Chem Phys 2021; 153:134111. [PMID: 33032416 DOI: 10.1063/5.0023609] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The excited-state properties and photoinduced charge-transfer (CT) kinetics in a series of symmetrical and asymmetrical Zn- and Au-ligated meso-meso-connected bacteriochlorin (BChl) complexes are studied computationally. BChl derivatives, which are excellent near-IR absorbing chromophores, are found to play a central role in bacterial photosynthetic reaction centers but are rarely used in artificial solar energy harvesting systems. The optical properties of chemically linked BChl complexes can be tuned by varying the linking group and involving different ligated metal ions. We investigate charge transfer in BChl dyads that are either directly linked or through a phenylene ring (1,4-phenylene) and which are ligating Zn or Au ions. The directly linked dyads with a nearly perpendicular arrangement of the BChl units bear markedly different properties than phenylene linked dyads. In addition, we find that the dielectric dependence of the intramolecular CT rate is very strong in neutral Zn-ligated dyads, whereas cationic Au-ligated dyads show negligible dielectric dependence of the CT rate. Rate constants of the photo induced CT process are calculated at the semiclassical Marcus level and are compared to fully quantum mechanical Fermi's golden rule based values. The rates are calculated using a screened range separated hybrid functional that offers a consistent framework for addressing environment polarization. We study solvated systems in two solvents of a low and a high scalar dielectric constant.
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Affiliation(s)
- Huseyin Aksu
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242-0001, USA
| | - Buddhadev Maiti
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242-0001, USA
| | - Marcin Ptaszek
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore, Maryland 21250-1000, USA
| | - Barry D Dunietz
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242-0001, USA
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Tamura H, Saito K, Ishikita H. The origin of unidirectional charge separation in photosynthetic reaction centers: nonadiabatic quantum dynamics of exciton and charge in pigment-protein complexes. Chem Sci 2021; 12:8131-8140. [PMID: 34194703 PMCID: PMC8208306 DOI: 10.1039/d1sc01497h] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/03/2021] [Indexed: 11/21/2022] Open
Abstract
Exciton charge separation in photosynthetic reaction centers from purple bacteria (PbRC) and photosystem II (PSII) occurs exclusively along one of the two pseudo-symmetric branches (active branch) of pigment-protein complexes. The microscopic origin of unidirectional charge separation in photosynthesis remains controversial. Here we elucidate the essential factors leading to unidirectional charge separation in PbRC and PSII, using nonadiabatic quantum dynamics calculations in conjunction with time-dependent density functional theory (TDDFT) with the quantum mechanics/molecular mechanics/polarizable continuum model (QM/MM/PCM) method. This approach accounts for energetics, electronic coupling, and vibronic coupling of the pigment excited states under electrostatic interactions and polarization of whole protein environments. The calculated time constants of charge separation along the active branches of PbRC and PSII are similar to those observed in time-resolved spectroscopic experiments. In PbRC, Tyr-M210 near the accessary bacteriochlorophyll reduces the energy of the intermediate state and drastically accelerates charge separation overcoming the electron-hole interaction. Remarkably, even though both the active and inactive branches in PSII can accept excitons from light-harvesting complexes, charge separation in the inactive branch is prevented by a weak electronic coupling due to symmetry-breaking of the chlorophyll configurations. The exciton in the inactive branch in PSII can be transferred to the active branch via direct and indirect pathways. Subsequently, the ultrafast electron transfer to pheophytin in the active branch prevents exciton back transfer to the inactive branch, thereby achieving unidirectional charge separation.
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Affiliation(s)
- Hiroyuki Tamura
- Department of Applied Chemistry, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8654 Japan
- Research Center for Advanced Science and Technology, The University of Tokyo 4-6-1 Komaba, Meguro-ku Tokyo 153-8904 Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8654 Japan
- Research Center for Advanced Science and Technology, The University of Tokyo 4-6-1 Komaba, Meguro-ku Tokyo 153-8904 Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8654 Japan
- Research Center for Advanced Science and Technology, The University of Tokyo 4-6-1 Komaba, Meguro-ku Tokyo 153-8904 Japan
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Brütting M, Foerster JM, Kümmel S. Investigating Primary Charge Separation in the Reaction Center of Heliobacterium modesticaldum. J Phys Chem B 2021; 125:3468-3475. [PMID: 33788561 DOI: 10.1021/acs.jpcb.0c10283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We compute the primary charge separation step in the homodimeric reaction center (RC) of Heliobacterium modesticaldum from first principles. Using time-dependent density functional theory with the optimally tuned range-separated hybrid functional ωPBE, we calculate the excitations of a system comprising the special pair, the adjacent accessory bacteriochlorophylls, and the most relevant parts of the surrounding protein environment. The structure of the excitation spectrum can be rationalized from coupling of the individual bacteriochlorophyll pigments similar to molecular J- and H-aggregates. We find excited states corresponding to forward-charge transfer along the individual branches of the RC of H. modesticaldum. In the spectrum, these are located at an energy between the coupled Qy and Qx transitions. With ab initio Born-Oppenheimer molecular dynamics simulations, we reveal the influence of thermal vibrations on the excited states. The results show that the energy gap between the coupled Qy and the forward-charge transfer excitations is ∼0.4 eV, which we consider to conflict with the concept of a direct transfer mechanism. Our calculations, however, reveal a certain spectral overlap of the forward-charge transfer and the coupled Qx excitations. The reliability and robustness of the results are demonstrated by several numerical tests.
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Robust design of D-π-A model compounds using digital structures for organic DSSC applications. J Mol Graph Model 2020; 102:107798. [PMID: 33181422 DOI: 10.1016/j.jmgm.2020.107798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 11/02/2020] [Accepted: 11/02/2020] [Indexed: 12/18/2022]
Abstract
New D-π-spacer-A model compound dye sensitizers (or dyes) are developed using digital structures for organic dyes sensitized solar cells (DSSCs) applications. Based on our previous studies, the model D-π-spacer-A dyes contain building blocks of a di(<i>p</i>-carboxy)-phenylamine as the electron donor and a perylene monoimide as the electron acceptor. The new D-π-spacer-A dyes are constructed through variations of a set of three model π-spacer units, fluorene, 3,4-ethylenedioxythiophene and thiophene. The new dyes are presented by digital structures of π(ijk) in a digital control Π-matrix. If the chromophore database of the π-units is arranged in a defined manner, the new dyes are therefore designed through selecting of the set of three integers (ijk). Properties such as the UV-vis spectra which are calculated using the time-dependent density functional theory (TD-DFT) determine if the new compounds are suitable for organic solar cell purposes. The same strategy can be applied to donors and acceptors in the D-π-spacer-A model compound in order to robust design and build new organic dyes for DSSCs. The digital structures of the organic compounds enhance the machine driven structure-property relationship establishment once the database is sufficiently comprehensive. The present study demonstrates that new compounds obtained through mixing the π-spacer units of fluorene, 3,4-ethylenedioxythiophene and thiophene, e.g. π121 and π211, result in better dyes in DSSC applications. The concise digital structures of the new dyes are able to achieve a more robust design of the organic dyes and other materials.
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Zieleniewska A, Zhao X, Bauroth S, Wang C, Batsanov AS, Krick Calderon C, Kahnt A, Clark T, Bryce MR, Guldi DM. Resonance-Enhanced Charge Delocalization in Carbazole-Oligoyne-Oxadiazole Conjugates. J Am Chem Soc 2020; 142:18769-18781. [PMID: 33084308 DOI: 10.1021/jacs.0c04003] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
There are notably few literature reports of electron donor-acceptor oligoynes, even though they offer unique opportunities for studying charge transport through "all-carbon" molecular bridges. In this context, the current study focuses on a series of carbazole-(C≡C)n-2,5-diphenyl-1,3,4-oxadiazoles (n = 1-4) as conjugated π-systems in general and explores their photophysical properties in particular. Contrary to the behavior of typical electron donor-acceptor systems, for these oligoynes, the rates of charge recombination after photoexcitation increase with increasing electron donor-acceptor distance. To elucidate this unusual performance, we conducted detailed photophysical and time-dependent density functional theory investigations. Significant delocalization of the molecular orbitals along the bridge indicates that the bridging states come into resonance with either the electron donor or acceptor, thereby accelerating the charge transfer. Moreover, the calculated bond lengths reveal a reduction in bond-length alternation upon photoexcitation, indicating significant cumulenic character of the bridge in the excited state. In short, strong vibronic coupling between the electron-donating N-arylcarbazoles and the electron-accepting 1,3,4-oxadiazoles accelerates the charge recombination as the oligoyne becomes longer.
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Affiliation(s)
- Anna Zieleniewska
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, Erlangen 91058, Germany
| | - Xiaotao Zhao
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Stefan Bauroth
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, Erlangen 91058, Germany
| | - Changsheng Wang
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Andrei S Batsanov
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Christina Krick Calderon
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, Erlangen 91058, Germany
| | - Axel Kahnt
- Leibniz Institute of Surface Engineering (IOM), Permoserstrasse 15, Leipzig 04318, Germany
| | - Timothy Clark
- Computer Chemistry Center, Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, Erlangen 91052, Germany
| | - Martin R Bryce
- Department of Chemistry, Durham University, Durham DH1 3LE, United Kingdom
| | - Dirk M Guldi
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, Erlangen 91058, Germany
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Zabelin AA, Khristin AM, Shkuropatova VA, Khatypov RA, Shkuropatov AY. Primary electron transfer in Rhodobacter sphaeroides R-26 reaction centers under dehydration conditions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148238. [PMID: 32533935 DOI: 10.1016/j.bbabio.2020.148238] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/28/2020] [Accepted: 06/03/2020] [Indexed: 11/26/2022]
Abstract
The photoinduced charge separation in QB-depleted reaction centers (RCs) from Rhodobacter sphaeroides R-26 in solid air-dried and vacuum-dried (~10-2 Torr) films, obtained in the presence of detergent n-dodecyl-β-D-maltoside (DM), is characterized using ultrafast transient absorption spectroscopy. It is shown that drying of RC-DM complexes is accompanied by reversible blue shifts of the ground-state absorption bands of the pigment ensemble, which suggest that no dehydration-induced structural destruction of RCs occurs in both types of films. In air-dried films, electron transfer from the excited primary electron donor P⁎ to the photoactive bacteriopheophytin HA proceeds in 4.7 ps to form the P+HA- state with essentially 100% yield. P+HA- decays in 260 ps both by electron transfer to the primary quinone QA to give the state P+QA- (87% yield) and by charge recombination to the ground state (13% yield). In vacuum-dried films, P⁎ decay is characterized by two kinetic components with time constants of 4.1 and 46 ps in a proportion of ~55%/45%, and P+HA- decays about 2-fold slower (462 ps) than in air-dried films. Deactivation of both P⁎ and P+HA- to the ground state effectively competes with the corresponding forward electron-transfer reactions in vacuum-dried RCs, reducing the yield of P+QA- to 68%. The results are compared with the data obtained for fully hydrated RCs in solution and are discussed in terms of the presence in the RC complexes of different water molecules, the removal/displacement of which affects spectral properties of pigment cofactors and rates and yields of the electron-transfer reactions.
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Affiliation(s)
- Alexey A Zabelin
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Anton M Khristin
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Valentina A Shkuropatova
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Ravil A Khatypov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation
| | - Anatoly Ya Shkuropatov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", 142290 Pushchino, Moscow Region, Russian Federation.
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29
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Femtosecond visible transient absorption spectroscopy of chlorophyll- f-containing photosystem II. Proc Natl Acad Sci U S A 2020; 117:23158-23164. [PMID: 32868421 DOI: 10.1073/pnas.2006016117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The recently discovered, chlorophyll-f-containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll-a We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll-a to the long-wavelength chlorophylls-f/d The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay. An ∼675-nm bleach attributed to the loss of chl-a absorption due to the formation of a cation radical, PD1 +•, is only fully developed in the nanosecond spectra, indicating an unusually delayed formation. A major spectral feature on the nanosecond timescale at 725 nm is attributed to an electrochromic blue shift of a FR-chlorophyll among the reaction center pigments. These time-resolved observations provide direct experimental support for the model of Nürnberg et al. [D. J. Nürnberg et al., Science 360, 1210-1213 (2018)], in which the primary electron donor is a FR-chlorophyll and the secondary donor is chlorophyll-a (PD1 of the central chlorophyll pair). Efficient charge separation also occurs using selective excitation of long-wavelength chlorophylls-f/d, and the localization of the excited state on P720* points to a smaller (entropic) energy loss compared to conventional PSII, where the excited state is shared over all of the chlorin pigments. This has important repercussions on understanding the overall energetics of excitation energy transfer and charge separation reactions in FR-PSII.
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30
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Acquirement of water-splitting ability and alteration of the charge-separation mechanism in photosynthetic reaction centers. Proc Natl Acad Sci U S A 2020; 117:16373-16382. [PMID: 32601233 PMCID: PMC7368266 DOI: 10.1073/pnas.2000895117] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
In photosynthetic reaction centers from purple bacteria (PbRC) and the water-oxidizing enzyme, photosystem II (PSII), charge separation occurs along one of the two symmetrical electron-transfer branches. Here we report the microscopic origin of the unidirectional charge separation, fully considering electron-hole interaction, electronic coupling of the pigments, and electrostatic interaction with the polarizable entire protein environments. The electronic coupling between the pair of bacteriochlorophylls is large in PbRC, forming a delocalized excited state with the lowest excitation energy (i.e., the special pair). The charge-separated state in the active branch is stabilized by uncharged polar residues in the transmembrane region and charged residues on the cytochrome c 2 binding surface. In contrast, the accessory chlorophyll in the D1 protein (ChlD1) has the lowest excitation energy in PSII. The charge-separated state involves ChlD1 •+ and is stabilized predominantly by charged residues near the Mn4CaO5 cluster and the proceeding proton-transfer pathway. It seems likely that the acquirement of water-splitting ability makes ChlD1 the initial electron donor in PSII.
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31
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Liu J, Friebe VM, Frese RN, Jones MR. Polychromatic solar energy conversion in pigment-protein chimeras that unite the two kingdoms of (bacterio)chlorophyll-based photosynthesis. Nat Commun 2020; 11:1542. [PMID: 32210238 PMCID: PMC7093453 DOI: 10.1038/s41467-020-15321-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 03/03/2020] [Indexed: 12/01/2022] Open
Abstract
Natural photosynthesis can be divided between the chlorophyll-containing plants, algae and cyanobacteria that make up the oxygenic phototrophs and a diversity of bacteriochlorophyll-containing bacteria that make up the anoxygenic phototrophs. Photosynthetic light harvesting and reaction centre proteins from both kingdoms have been exploited for solar energy conversion, solar fuel synthesis and sensing technologies, but the energy harvesting abilities of these devices are limited by each protein's individual palette of pigments. In this work we demonstrate a range of genetically-encoded, self-assembling photosystems in which recombinant plant light harvesting complexes are covalently locked with reaction centres from a purple photosynthetic bacterium, producing macromolecular chimeras that display mechanisms of polychromatic solar energy harvesting and conversion. Our findings illustrate the power of a synthetic biology approach in which bottom-up construction of photosystems using naturally diverse but mechanistically complementary components can be achieved in a predictable fashion through the encoding of adaptable, plug-and-play covalent interfaces.
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Affiliation(s)
- Juntai Liu
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Vincent M Friebe
- Department of Physics and Astronomy, LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, Amsterdam, 1081 HV, The Netherlands
| | - Raoul N Frese
- Department of Physics and Astronomy, LaserLaB Amsterdam, VU University Amsterdam, De Boelelaan 1081, Amsterdam, 1081 HV, The Netherlands
| | - Michael R Jones
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
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32
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Marcheafave GG, Pauli ED, Tormena CD, Ortiz MCV, de Almeida AG, Rakocevic M, Bruns RE, Scarminio IS. Factorial design fingerprint discrimination of Coffea arabica beans under elevated carbon dioxide and limited water conditions. Talanta 2020; 209:120591. [DOI: 10.1016/j.talanta.2019.120591] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Revised: 10/28/2019] [Accepted: 11/23/2019] [Indexed: 10/25/2022]
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33
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Aksu H, Schubert A, Bhandari S, Yamada A, Geva E, Dunietz BD. On the Role of the Special Pair in Photosystems as a Charge Transfer Rectifier. J Phys Chem B 2020; 124:1987-1994. [PMID: 32109062 DOI: 10.1021/acs.jpcb.9b11431] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The special pair, a bacteriochlorophyll a (BChl) dimer found at the core of bacterial reaction centers, is known to play a key role in the functionality of photosystems as a precursor to the photosynthesis process. In this paper, we analyze the inherent affinity of the special pair to rectify the intrapair photo-induced charge transfer (CT). In particular, we show that the molecular environment affects the nuclear geometry, resulting in symmetry breaking between the two possible intrapair CT processes. To this end, we study the relationships of the intrapair CT and the molecular geometry with respect to the effective dielectric constant provided by the molecular environment. We identify the special pair structural feature that breaks the symmetry between the two molecules, leading to CT rectification. Excited state energies, oscillator strengths, and electronic coupling values are obtained via time-dependent density functional theory, employing a recently developed framework based on a screened range-separated hybrid functional within a polarizable continuum model (SRSH-PCM). We analyze the rectification capability of the special pair by calculating the CT rates using a first-principles-based Fermi's golden rule approach.
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Affiliation(s)
- Huseyin Aksu
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Alexander Schubert
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States.,Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Srijana Bhandari
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Atsushi Yamada
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 Japan
| | - Eitan Geva
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Barry D Dunietz
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
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34
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Switching sides-Reengineered primary charge separation in the bacterial photosynthetic reaction center. Proc Natl Acad Sci U S A 2019; 117:865-871. [PMID: 31892543 DOI: 10.1073/pnas.1916119117] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report 90% yield of electron transfer (ET) from the singlet excited state P* of the primary electron-donor P (a bacteriochlorophyll dimer) to the B-side bacteriopheophytin (HB) in the bacterial photosynthetic reaction center (RC). Starting from a platform Rhodobacter sphaeroides RC bearing several amino acid changes, an Arg in place of the native Leu at L185-positioned over one face of HB and only ∼4 Å from the 4 central nitrogens of the HB macrocycle-is the key additional mutation providing 90% yield of P+HB - This all but matches the near-unity yield of A-side P+HA - charge separation in the native RC. The 90% yield of ET to HB derives from (minimally) 3 P* populations with distinct means of P* decay. In an ∼40% population, P* decays in ∼4 ps via a 2-step process involving a short-lived P+BB - intermediate, analogous to initial charge separation on the A side of wild-type RCs. In an ∼50% population, P* → P+HB - conversion takes place in ∼20 ps by a superexchange mechanism mediated by BB An ∼10% population of P* decays in ∼150 ps largely by internal conversion. These results address the long-standing dichotomy of A- versus B-side initial charge separation in native RCs and have implications for the mechanism(s) and timescale of initial ET that are required to achieve a near-quantitative yield of unidirectional charge separation.
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Aksu H, Schubert A, Geva E, Dunietz BD. Explaining Spectral Asymmetries and Excitonic Characters of the Core Pigment Pairs in the Bacterial Reaction Center Using a Screened Range-Separated Hybrid Functional. J Phys Chem B 2019; 123:8970-8975. [DOI: 10.1021/acs.jpcb.9b07646] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Huseyin Aksu
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Alexander Schubert
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Eitan Geva
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Barry D. Dunietz
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
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Faries KM, Kohout CE, Wang GX, Hanson DK, Holten D, Laible PD, Kirmaier C. Consequences of saturation mutagenesis of the protein ligand to the B-side monomeric bacteriochlorophyll in reaction centers from Rhodobacter capsulatus. PHOTOSYNTHESIS RESEARCH 2019; 141:273-290. [PMID: 30859455 DOI: 10.1007/s11120-019-00626-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 02/07/2019] [Indexed: 06/09/2023]
Abstract
In bacterial reaction centers (RCs), photon-induced initial charge separation uses an A-side bacteriochlorophyll (BChl, BA) and bacteriopheophytin (BPh, HA), while the near-mirror image B-side BB and HB cofactors are inactive. Two new sets of Rhodobacter capsulatus RC mutants were designed, both bearing substitution of all amino acids for the native histidine M180 (M-polypeptide residue 180) ligand to the core Mg ion of BB. Residues are identified that largely result in retention of a BChl in the BB site (Asp, Ser, Pro, Gln, Asn, Gly, Cys, Lys, and Thr), ones that largely harbor the Mg-free BPh in the BB site (Leu and Ile), and ones for which isolated RCs are comprised of a substantial mixture of these two RC types (Ala, Glu, Val, Met and, in one set, Arg). No protein was isolated when M180 is Trp, Tyr, Phe, or (in one set) Arg. These findings are corroborated by ground state spectra, pigment extractions, ultrafast transient absorption studies, and the yields of B-side transmembrane charge separation. The changes in coordination chemistries did not reveal an RC with sufficiently precise poising of the redox properties of the BB-site cofactor to result in a high yield of B-side electron transfer to HB. Insights are gleaned into the amino acid properties that support BChl in the BB site and into the widely observed multi-exponential decay of the excited state of the primary electron donor. The results also have direct implications for tuning free energies of the charge-separated intermediates in RCs and mimetic systems.
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Affiliation(s)
- Kaitlyn M Faries
- Department of Chemistry, Washington University, St. Louis, MO, 63130, USA
| | - Claire E Kohout
- Biosciences Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Grace Xiyu Wang
- Biosciences Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Deborah K Hanson
- Biosciences Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Dewey Holten
- Department of Chemistry, Washington University, St. Louis, MO, 63130, USA
| | - Philip D Laible
- Biosciences Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Christine Kirmaier
- Department of Chemistry, Washington University, St. Louis, MO, 63130, USA.
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Suresh L, Vaghasiya JV, Nandakumar DK, Wu T, Jones MR, Tan SC. High-Performance UV Enhancer Molecules Coupled with Photosynthetic Proteins for Ultra-Low-Intensity UV Detection. Chem 2019. [DOI: 10.1016/j.chempr.2019.04.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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38
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Zabelin AA, Fufina TY, Khristin AM, Khatypov RA, Shkuropatova VA, Shuvalov VA, Vasilieva LG, Shkuropatov AY. Effect of Leucine M196 Substitution by Histidine on Electronic Structure of the Primary Electron Donor and Electron Transfer in Reaction Centers from Rhodobacter sphaeroides. BIOCHEMISTRY (MOSCOW) 2019; 84:520-528. [PMID: 31234766 DOI: 10.1134/s0006297919050067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In our recent X-ray study, we demonstrated that substitution of the natural leucine residue M196 with histidine in the reaction center (RC) from Rhodobacter (Rba.) sphaeroides leads to formation of a close contact between the genetically introduced histidine and the primary electron donor P (bacteriochlorophylls (BChls) PA and PB dimer) creating a novel pigment-protein interaction that is not observed in native RCs. In the present work, the possible nature of this novel interaction and its effects on the electronic properties of P and the photochemical charge separation in isolated mutant RCs L(M196)H are investigated at room temperature using steady-state absorption spectroscopy, light-induced difference FTIR spectroscopy, and femtosecond transient absorption spectroscopy. The results are compared with the data obtained for the RCs from Rba. sphaeroides pseudo-wild type strain. It is shown that the L(M196)H mutation results in a decrease in intensity and broadening of the long-wavelength Qy absorption band of P at ~865 nm. Due to the mutation, there is also weakening of the electronic coupling between BChls in the radical cation P+ and increase in the positive charge localization on the PA molecule. Despite the significant perturbations of the electronic structure of P, the mutant RCs retain high electron transfer rates and quantum yield of the P+QA- state (QA is the primary quinone acceptor), which is close to the one observed in the native RCs. Comparison of our results with the literature data suggests that the imidazole group of histidine M196 forms a π-hydrogen bond with the π-electron system of the PB molecule in the P dimer. It is likely that the specific (T-shaped) spatial organization of the π-hydrogen interaction and its potential heterogeneity in relation to the bonding energy is, at least partially, the reason that this type of interaction between the protein and the pigment and quinone cofactors is not realized in the native RCs.
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Affiliation(s)
- A A Zabelin
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - T Yu Fufina
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - A M Khristin
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - R A Khatypov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - V A Shkuropatova
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - V A Shuvalov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - L G Vasilieva
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - A Ya Shkuropatov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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39
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Photosynthetic apparatus of Rhodobacter sphaeroides exhibits prolonged charge storage. Nat Commun 2019; 10:902. [PMID: 30796237 PMCID: PMC6385238 DOI: 10.1038/s41467-019-08817-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 01/25/2019] [Indexed: 12/17/2022] Open
Abstract
Photosynthetic proteins have been extensively researched for solar energy harvesting. Though the light-harvesting and charge-separation functions of these proteins have been studied in depth, their potential as charge storage systems has not been investigated to the best of our knowledge. Here, we report prolonged storage of electrical charge in multilayers of photoproteins isolated from Rhodobacter sphaeroides. Direct evidence for charge build-up within protein multilayers upon photoexcitation and external injection is obtained by Kelvin-probe and scanning-capacitance microscopies. Use of these proteins is key to realizing a 'self-charging biophotonic device' that not only harvests light and photo-generates charges but also stores them. In strong correlation with the microscopic evidence, the phenomenon of prolonged charge storage is also observed in primitive power cells constructed from the purple bacterial photoproteins. The proof-of-concept power cells generated a photovoltage as high as 0.45 V, and stored charge effectively for tens of minutes with a capacitance ranging from 0.1 to 0.2 F m-2.
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40
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Liu J, Mantell J, Di Bartolo N, Jones MR. Mechanisms of Self-Assembly and Energy Harvesting in Tuneable Conjugates of Quantum Dots and Engineered Photovoltaic Proteins. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1804267. [PMID: 30569587 DOI: 10.1002/smll.201804267] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 11/30/2018] [Indexed: 06/09/2023]
Abstract
Photoreaction centers facilitate the solar energy transduction at the heart of photosynthesis and there is increasing interest in their incorporation into biohybrid devices for solar energy conversion, sensing, and other applications. In this work, the self-assembly of conjugates between engineered bacterial reaction centers (RCs) and quantum dots (QDs) that act as a synthetic light harvesting system is described. The interface between protein and QD is provided by a polyhistidine tag that confers a tight and specific binding and defines the geometry of the interaction. Protein engineering that changes the pigment composition of the RC is used to identify Förster resonance energy transfer as the mechanism through which QDs can drive RC photochemistry with a high energy transfer efficiency. A thermodynamic explanation of RC/QD conjugation based on a multiple/independent binding model is provided. It is also demonstrated that the presence of multiple binding sites affects energy coupling not only between RCs and QDs but also among the bound RCs themselves, effects which likely stem from restricted RC dynamics at the QD surface in denser conjugates. These findings are readily transferrable to many other conjugate systems between proteins or combinations of proteins and other nanomaterials.
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Affiliation(s)
- Juntai Liu
- School of Biochemistry Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Judith Mantell
- Wolfson Bioimaging Facility, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Natalie Di Bartolo
- School of Biochemistry Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Michael R Jones
- School of Biochemistry Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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41
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Richter M, Fingerhut BP. Coupled excitation energy and charge transfer dynamics in reaction centre inspired model systems. Faraday Discuss 2019; 216:72-93. [PMID: 31012450 DOI: 10.1039/c8fd00189h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Functional operation conditions of reaction centre core complexes require the tight coupling of exciton states to concomitant charge separation. Rigorous theoretical treatment of such integrated excitation energy transfer (EET) and charge transfer (CT) dynamics is particularly challenging due to (i) appreciable system sizes, (ii) inter-site and system-bath couplings of similar magnitude that render the Born-Markov approximation invalid, (iii) substantial reorganization energies of CT states, and (iv) the presence of complex structured spectral densities due to vibrational modes of the surroundings. We present numerical simulations on bacterial reaction centre (bRC) inspired model systems that utilize the recently developed MACGIC-iQUAPI method [Richter et al., J. Chem. Phys., 2017, 146, 214101]. The simulations demonstrate that the method provides a rigorous framework for the investigation of such integrated EET-CT dynamics. First, the applicability of the MACGIC-iQUAPI method is explored for a transition from monotonically decaying to oscillatory system-bath influence coefficients, a behavior inherently imposed by structured bath spectral densities. Tightly coupled EET and CT dynamics is further addressed for an excitonic subsystem that resembles strong coupling of special pair states and serves as donor towards a generic bridge-acceptor system. By solving the dissipative quantum dynamics of such bRC inspired model systems, the quenching of excitonic coherence on the hundreds of femtoseconds timescale is explored via a variation of the bridge state energetics, resembling a continuous transition from sequential to superexchange mediated CT regimes. Further, the simulations explore the influence of resonant vibrational modes on the quenching of excitonic coherence via CT. The results reveal a moderate influence of vibrational mode on charge separation dynamics in regimes of biologically relevant EET and CT dynamics.
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Affiliation(s)
- Martin Richter
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
| | - Benjamin P Fingerhut
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany.
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42
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Białek R, Swainsbury DJK, Wiesner M, Jones MR, Gibasiewicz K. Modelling of the cathodic and anodic photocurrents from Rhodobacter sphaeroides reaction centres immobilized on titanium dioxide. PHOTOSYNTHESIS RESEARCH 2018; 138:103-114. [PMID: 29971571 PMCID: PMC6208573 DOI: 10.1007/s11120-018-0550-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 06/21/2018] [Indexed: 06/08/2023]
Abstract
As one of a number of new technologies for the harnessing of solar energy, there is interest in the development of photoelectrochemical cells based on reaction centres (RCs) from photosynthetic organisms such as the bacterium Rhodobacter (Rba.) sphaeroides. The cell architecture explored in this report is similar to that of a dye-sensitized solar cell but with delivery of electrons to a mesoporous layer of TiO2 by natural pigment-protein complexes rather than an artificial dye. Rba. sphaeroides RCs were bound to the deposited TiO2 via an engineered extramembrane peptide tag. Using TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) as an electrolyte, these biohybrid photoactive electrodes produced an output that was the net product of cathodic and anodic photocurrents. To explain the observed photocurrents, a kinetic model is proposed that includes (1) an anodic current attributed to injection of electrons from the triplet state of the RC primary electron donor (PT) to the TiO2 conduction band, (2) a cathodic current attributed to reduction of the photooxidized RC primary electron donor (P+) by surface states of the TiO2 and (3) transient cathodic and anodic current spikes due to oxidation/reduction of TMPD/TMPD+ at the conductive glass (FTO) substrate. This model explains the origin of the photocurrent spikes that appear in this system after turning illumination on or off, the reason for the appearance of net positive or negative stable photocurrents depending on experimental conditions, and the overall efficiency of the constructed cell. The model may be a used as a guide for improvement of the photocurrent efficiency of the presented system as well as, after appropriate adjustments, other biohybrid photoelectrodes.
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Affiliation(s)
- Rafał Białek
- Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Umultowska 85, 61-614, Poznan, Poland.
| | - David J K Swainsbury
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - Maciej Wiesner
- Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Umultowska 85, 61-614, Poznan, Poland
- NanoBioMedical Center, Adam Mickiewicz University in Poznań, ul. Umultowska 85, 61-614, Poznan, Poland
| | - Michael R Jones
- School of Biochemistry, Biomedical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
| | - Krzysztof Gibasiewicz
- Faculty of Physics, Adam Mickiewicz University in Poznań, ul. Umultowska 85, 61-614, Poznan, Poland.
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43
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Konar A, Sechrist R, Song Y, Policht VR, Laible PD, Bocian DF, Holten D, Kirmaier C, Ogilvie JP. Electronic Interactions in the Bacterial Reaction Center Revealed by Two-Color 2D Electronic Spectroscopy. J Phys Chem Lett 2018; 9:5219-5225. [PMID: 30136848 DOI: 10.1021/acs.jpclett.8b02394] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The bacterial reaction center (BRC) serves as an important model system for understanding the charge separation processes in photosynthesis. Knowledge of the electronic structure of the BRC is critical for understanding its charge separation mechanism. While it is well-accepted that the "special pair" pigments are strongly coupled, the degree of coupling among other BRC pigments has been thought to be relatively weak. Here we study the W(M250)V mutant BRC by two-color two-dimensional electronic spectroscopy to correlate changes in the Q x region with excitation of the Q y transitions. The resulting Q y-Q x cross-peaks provide a sensitive measure of the electronic interactions throughout the BRC pigment network and complement one-color 2D studies in which such interactions are often obscured by energy transfer and excited-state absorption signals. Our observations should motivate the refinement of electronic structure models of the BRC to facilitate improved understanding of the charge separation mechanism.
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Affiliation(s)
- Arkaprabha Konar
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Riley Sechrist
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Yin Song
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Veronica R Policht
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Philip D Laible
- Biosciences Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - David F Bocian
- Department of Chemistry , University of California , Riverside , California 92521 , United States
| | - Dewey Holten
- Department of Chemistry , Washington University , St. Louis , Missouri 63130 , United States
| | - Christine Kirmaier
- Department of Chemistry , Washington University , St. Louis , Missouri 63130 , United States
| | - Jennifer P Ogilvie
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
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44
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Ma F, Romero E, Jones MR, Novoderezhkin VI, van Grondelle R. Vibronic Coherence in the Charge Separation Process of the Rhodobacter sphaeroides Reaction Center. J Phys Chem Lett 2018; 9:1827-1832. [PMID: 29584941 PMCID: PMC6023262 DOI: 10.1021/acs.jpclett.8b00108] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 03/27/2018] [Indexed: 05/19/2023]
Abstract
Two-dimensional electronic spectroscopy was applied to a variant of the reaction center (RC) of purple bacterium Rhodobacter sphaeroides lacking the primary acceptor ubiquinone in order to understand the ultrafast separation and transfer of charge between the bacteriochlorin cofactors. For the first time, characteristic 2D spectra were obtained for the participating excited and charge-transfer states, and the electron-transfer cascade (including two different channels, the P* and B* channels) was fully mapped. By analyzing quantum beats using 2D frequency maps, excited-state vibrational modes at 153 and 33 cm-1 were identified. We speculate that these modes couple to the charge separation (CS) process and collectively optimize the CS and are responsible for the superhigh efficiency.
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Affiliation(s)
- Fei Ma
- Department of Physics and Astronomy , Faculty of Sciences, VU University Amsterdam , De Boelelaan 1081 , 1081 HV Amsterdam , The Netherlands
| | - Elisabet Romero
- Department of Physics and Astronomy , Faculty of Sciences, VU University Amsterdam , De Boelelaan 1081 , 1081 HV Amsterdam , The Netherlands
| | - Michael R Jones
- School of Biochemistry , University of Bristol , Biomedical Sciences Building, University Walk, Bristol BS8 1TD , United Kingdom
| | - Vladimir I Novoderezhkin
- A. N. Belozersky Institute of Physico-Chemical Biology , Moscow State University , Leninskie Gory , 119992 Moscow , Russia
| | - Rienk van Grondelle
- Department of Physics and Astronomy , Faculty of Sciences, VU University Amsterdam , De Boelelaan 1081 , 1081 HV Amsterdam , The Netherlands
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45
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Liu J, Friebe V, Swainsbury DJK, Crouch LI, Szabo DA, Frese RN, Jones MR. Engineered photoproteins that give rise to photosynthetically-incompetent bacteria are effective as photovoltaic materials for biohybrid photoelectrochemical cells. Faraday Discuss 2018; 207:307-327. [PMID: 29364305 PMCID: PMC5903125 DOI: 10.1039/c7fd00190h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 09/04/2017] [Indexed: 01/27/2023]
Abstract
Reaction centre/light harvesting proteins such as the RCLH1X complex from Rhodobacter sphaeroides carry out highly quantum-efficient conversion of solar energy through ultrafast energy transfer and charge separation, and these pigment-proteins have been incorporated into biohybrid photoelectrochemical cells for a variety of applications. In this work we demonstrate that, despite not being able to support normal photosynthetic growth of Rhodobacter sphaeroides, an engineered variant of this RCLH1X complex lacking the PufX protein and with an enlarged light harvesting antenna is unimpaired in its capacity for photocurrent generation in two types of bio-photoelectrochemical cells. Removal of PufX also did not impair the ability of the RCLH1 complex to act as an acceptor of energy from synthetic light harvesting quantum dots. Unexpectedly, the removal of PufX led to a marked improvement in the overall stability of the RCLH1 complex under heat stress. We conclude that PufX-deficient RCLH1 complexes are fully functional in solar energy conversion in a device setting and that their enhanced structural stability could make them a preferred choice over their native PufX-containing counterpart. Our findings on the competence of RCLH1 complexes for light energy conversion in vitro are discussed with reference to the reason why these PufX-deficient proteins are not capable of light energy conversion in vivo.
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Affiliation(s)
- Juntai Liu
- School of Biochemistry , University of Bristol , Medical Sciences Building, University Walk , Bristol BS8 1TD , UK .
| | - Vincent M. Friebe
- Department of Physics and Astronomy , LaserLaB Amsterdam , VU University Amsterdam , De Boelelaan 1081, 1081 HV , Amsterdam , The Netherlands
| | - David J. K. Swainsbury
- School of Biochemistry , University of Bristol , Medical Sciences Building, University Walk , Bristol BS8 1TD , UK .
| | - Lucy I. Crouch
- School of Biochemistry , University of Bristol , Medical Sciences Building, University Walk , Bristol BS8 1TD , UK .
| | - David A. Szabo
- School of Biochemistry , University of Bristol , Medical Sciences Building, University Walk , Bristol BS8 1TD , UK .
| | - Raoul N. Frese
- Department of Physics and Astronomy , LaserLaB Amsterdam , VU University Amsterdam , De Boelelaan 1081, 1081 HV , Amsterdam , The Netherlands
| | - Michael R. Jones
- School of Biochemistry , University of Bristol , Medical Sciences Building, University Walk , Bristol BS8 1TD , UK .
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46
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McCleese C, Yu Z, Esemoto NN, Kolodziej C, Maiti B, Bhandari S, Dunietz BD, Burda C, Ptaszek M. Excitonic Interactions in Bacteriochlorin Homo-Dyads Enable Charge Transfer: A New Approach to the Artificial Photosynthetic Special Pair. J Phys Chem B 2018. [PMID: 29526105 DOI: 10.1021/acs.jpcb.8b02123] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Excitonically coupled bacteriochlorin (BC) dimers constitute a primary electron donor (special pair) in bacterial photosynthesis and absorbing units in light-harvesting antenna. However, the exact nature of the excited state of these dyads is still not fully understood. Here, we report a detailed spectroscopic and computational investigation of a series of symmetrical bacteriochlorin dimers, where the bacteriochlorins are connected either directly or by a phenylene bridge of variable length. The excited state of these dyads is quenched in high-dielectric solvents, which we attribute to photoinduced charge transfer. The mixing of charge transfer with the excitonic state causes accelerated (within 41 ps) decay of the excited state for the directly linked dyad, which is reduced by orders of magnitude with each additional phenyl ring separating the bacteriochlorins. These results highlight the origins of the excited-state dynamics in symmetric BC dyads and provide a new model for studying the primary processes in photosynthesis and for the development of artificial, biomimetic systems for solar energy conversion.
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Affiliation(s)
- Christopher McCleese
- Department of Chemistry , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Zhanqian Yu
- Department of Chemistry and Biochemistry , University of Maryland , Baltimore County, Baltimore , Maryland 21250 , United States
| | - Nopondo N Esemoto
- Department of Chemistry and Biochemistry , University of Maryland , Baltimore County, Baltimore , Maryland 21250 , United States
| | - Charles Kolodziej
- Department of Chemistry , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Buddhadev Maiti
- Department of Chemistry and Biochemistry , Kent State University , Kent , Ohio 44242 , United States
| | - Srijana Bhandari
- Department of Chemistry and Biochemistry , Kent State University , Kent , Ohio 44242 , United States
| | - Barry D Dunietz
- Department of Chemistry and Biochemistry , Kent State University , Kent , Ohio 44242 , United States
| | - Clemens Burda
- Department of Chemistry , Case Western Reserve University , Cleveland , Ohio 44106 , United States
| | - Marcin Ptaszek
- Department of Chemistry and Biochemistry , University of Maryland , Baltimore County, Baltimore , Maryland 21250 , United States
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47
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Ma F, Swainsbury DJK, Jones MR, van Grondelle R. Photoprotection through ultrafast charge recombination in photochemical reaction centres under oxidizing conditions. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0378. [PMID: 28808097 DOI: 10.1098/rstb.2016.0378] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/03/2017] [Indexed: 11/12/2022] Open
Abstract
Engineering natural photosynthesis to address predicted shortfalls in food and energy supply requires a detailed understanding of its molecular basis and the intrinsic photoprotective mechanisms that operate under fluctuating environmental conditions. Long-lived triplet or singlet excited electronic states have the potential to cause photodamage, particularly in the presence of oxygen, and so a variety of mechanisms exist to prevent formation of such states or safely dissipate their energy. Here, we report a dramatic difference in spectral evolution in fully reduced and partially oxidized Rhodobacter sphaeroides reaction centres (RCs) following excitation of the monomeric bacteriochlorophyll (BChl) cofactors at 805 nm. Three types of preparation were studied, including RCs purified as protein/lipid nanodiscs using the copolymer styrene maleic acid. In fully reduced RCs such excitation produces membrane-spanning charge separation. In preparations of partially oxidized RCs the spectroscopic signature of this charge separation is replaced by that of an energy dissipation process, including in the majority sub-population of reduced RCs. This process, which appears to take place on both cofactor branches, involves formation of a BChl+/bacteriopheophytin- radical pair that dissipates energy via recombination to a vibrationally hot ground state. The possible physiological role of this dissipative process under mildly oxidizing conditions is considered.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'.
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Affiliation(s)
- Fei Ma
- Department of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - David J K Swainsbury
- School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Rienk van Grondelle
- Department of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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48
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Primary processes in the bacterial reaction center probed by two-dimensional electronic spectroscopy. Proc Natl Acad Sci U S A 2018; 115:3563-3568. [PMID: 29555738 DOI: 10.1073/pnas.1721927115] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the initial steps of photosynthesis, reaction centers convert solar energy to stable charge-separated states with near-unity quantum efficiency. The reaction center from purple bacteria remains an important model system for probing the structure-function relationship and understanding mechanisms of photosynthetic charge separation. Here we perform 2D electronic spectroscopy (2DES) on bacterial reaction centers (BRCs) from two mutants of the purple bacterium Rhodobacter capsulatus, spanning the Q y absorption bands of the BRC. We analyze the 2DES data using a multiexcitation global-fitting approach that employs a common set of basis spectra for all excitation frequencies, incorporating inputs from the linear absorption spectrum and the BRC structure. We extract the exciton energies, resolving the previously hidden upper exciton state of the special pair. We show that the time-dependent 2DES data are well-represented by a two-step sequential reaction scheme in which charge separation proceeds from the excited state of the special pair (P*) to P+HA- via the intermediate P+BA- When inhomogeneous broadening and Stark shifts of the B* band are taken into account we can adequately describe the 2DES data without the need to introduce a second charge-separation pathway originating from the excited state of the monomeric bacteriochlorophyll BA*.
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49
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Ravi SK, Swainsbury DJK, Singh VK, Ngeow YK, Jones MR, Tan SC. A Mechanoresponsive Phase-Changing Electrolyte Enables Fabrication of High-Output Solid-State Photobioelectrochemical Devices from Pigment-Protein Multilayers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:1704073. [PMID: 29250868 DOI: 10.1002/adma.201704073] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 09/12/2017] [Indexed: 06/07/2023]
Abstract
Exploitation of natural photovoltaic reaction center pigment proteins in biohybrid architectures for solar energy harvesting is attractive due to their global abundance, environmental compatibility, and near-unity quantum efficiencies. However, it is challenging to achieve high photocurrents in a device setup due to limitations imposed by low light absorbance by protein monolayers and/or slow long-range diffusion of liquid-phase charge carriers. In an attempt to enhance the photocurrent density achievable by pigment proteins, here, an alternative solid-state device architecture enabled by a mechanoresponsive gel electrolyte that can be applied under nondenaturing conditions is demonstrated. The phase-changing electrolyte gel provides a pervading biocompatible interface for charge conduction through highly absorbing protein multilayers that are fabricated in a simple fashion. Assembled devices exhibit enhanced current stability and a maximal photoresponse of ≈860 µA cm-2 , a fivefold improvement over the best previous comparable devices under standard illumination conditions. Photocurrent generation is enhanced by directional energy transfer through extended layers of light-harvesting complexes, mimicking the modular antenna/transducer architecture of natural photosystems, and by metastable radical pair formation when photovoltaic reaction centers are embedded throughout light-harvesting regions of the device.
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Affiliation(s)
- Sai Kishore Ravi
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - David J K Swainsbury
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Varun Kumar Singh
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Yoke Keng Ngeow
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore
| | - Michael R Jones
- School of Biochemistry, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Swee Ching Tan
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
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50
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Rancova O, Jankowiak R, Abramavicius D. Role of Bath Fluctuations in the Double-Excitation Manifold in Shaping the 2DES of Bacterial Reaction Centers at Low Temperature. J Phys Chem B 2018; 122:1348-1366. [DOI: 10.1021/acs.jpcb.7b08905] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Olga Rancova
- Institute
of Chemical Physics, Vilnius University, Sauletekio al 9-III, 10222 Vilnius, Lithuania
| | - Ryszard Jankowiak
- Department
of Chemistry and Department of Physics, Kansas State University, 213 CBC Building, Manhattan, Kansas 66506-0401, United States
| | - Darius Abramavicius
- Institute
of Chemical Physics, Vilnius University, Sauletekio al 9-III, 10222 Vilnius, Lithuania
| |
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