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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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Ouyang B, Wei D, Wu B, Yan L, Gang H, Cao Y, Chen P, Zhang T, Wang H. In the View of Electrons Transfer and Energy Conversion: The Antimicrobial Activity and Cytotoxicity of Metal-Based Nanomaterials and Their Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2303153. [PMID: 37721195 DOI: 10.1002/smll.202303153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 08/28/2023] [Indexed: 09/19/2023]
Abstract
The global pandemic and excessive use of antibiotics have raised concerns about environmental health, and efforts are being made to develop alternative bactericidal agents for disinfection. Metal-based nanomaterials and their derivatives have emerged as promising candidates for antibacterial agents due to their broad-spectrum antibacterial activity, environmental friendliness, and excellent biocompatibility. However, the reported antibacterial mechanisms of these materials are complex and lack a comprehensive understanding from a coherent perspective. To address this issue, a new perspective is proposed in this review to demonstrate the toxic mechanisms and antibacterial activities of metal-based nanomaterials in terms of energy conversion and electron transfer. First, the antimicrobial mechanisms of different metal-based nanomaterials are discussed, and advanced research progresses are summarized. Then, the biological intelligence applications of these materials, such as biomedical implants, stimuli-responsive electronic devices, and biological monitoring, are concluded based on trappable electrical signals from electron transfer. Finally, current improvement strategies, future challenges, and possible resolutions are outlined to provide new insights into understanding the antimicrobial behaviors of metal-based materials and offer valuable inspiration and instructional suggestions for building future intelligent environmental health.
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Affiliation(s)
- Baixue Ouyang
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Dun Wei
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Bichao Wu
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Lvji Yan
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Haiying Gang
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Yiyun Cao
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Peng Chen
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Tingzheng Zhang
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
| | - Haiying Wang
- School of Metallurgy and Environment, Central South University, Changsha, 410083, P. R. China
- School of Metallurgy and Environment and Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution, Central South, University, Changsha, 410083, China
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4
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Kundu P, Saha S, Gangopadhyay G. A minimal kinetic model for the interpretation of complex catalysis in single enzyme molecules. Phys Chem Chem Phys 2023; 26:463-476. [PMID: 38078459 DOI: 10.1039/d3cp01720f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Multi-exponential waiting-time distribution and randomness parameter greater than unity ascribe dynamic disorder in single-enzyme catalysis corroborated to the interplay of transforming conformers [English et al., Nat. Chem. Biol., 2006, 2, 87]. The associated multi-state model of enzymatic turnovers with statically heterogeneous catalytic rates misdescribes the non-linear uprising of the randomness parameter from unity in relation to the attributes of the fall-offs of the waiting-time distribution at different substrate concentrations. To resolve this crucial issue, we first employ a comprehensive stochastic reaction scenario and further rationalize and work out the minimal indispensable dynamic-disorder model that ensures the foregoing relationship upon comparison with the data. We elucidate that specific disregard for the transition rate coefficients in the multi-state model on account of the especially slow conformational transitions is the underlying reason for not achieving interrelation between the observables.
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Affiliation(s)
- Prasanta Kundu
- S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
| | - Soma Saha
- Department of Chemistry, Presidency University, 86/1 College Street, Kolkata 700073, India.
| | - Gautam Gangopadhyay
- S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
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5
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Zhang Y, Yang J, Liu N, Wang L, Lu F, Chen J, Zhong D. Ultrafast Nonequilibrium Dynamics of Vibrationally Hot Electron Transfer in Flavodoxin. J Phys Chem Lett 2023; 14:10657-10663. [PMID: 38031667 DOI: 10.1021/acs.jpclett.3c02438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
The understanding of ultrafast short-range electron transfer (ET) in proteins remains challenging, and thorough studies on well-defined biological systems are demanding. Here, we utilized two types of flavodoxins and designed a series of mutants on two positions to systematically characterize the complete photoinduced redox cycles. We identified one position with a favorable orientation and distance for ultrafast ET in a few femtoseconds and the other position is relatively flexible with a longer ET time scale. We found that all forward and back ET dynamics are ultrafast nonequilibrium processes, occurring through highly vibronic states and ending in vibrationally hot ground states with subsequent cooling relaxation to efficiently dissipate photon energy into the protein environment.
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Affiliation(s)
- Yifei Zhang
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jie Yang
- College of Science, Nanjing Forestry University, Nanjing 210037, China
| | - Na Liu
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lijuan Wang
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, United States
| | - Faming Lu
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jie Chen
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dongping Zhong
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
- Department of Physics, Department of Chemistry and Biochemistry, and Program of Biophysics, Program of Chemical Physics, and Program of Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
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6
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Ye ZP, Stirbet A, An T, Robakowski P, Kang HJ, Yang XL, Wang FB. Investigation on absorption cross-section of photosynthetic pigment molecules based on a mechanistic model of the photosynthetic electron flow-light response in C 3, C 4 species and cyanobacteria grown under various conditions. FRONTIERS IN PLANT SCIENCE 2023; 14:1234462. [PMID: 37711288 PMCID: PMC10497745 DOI: 10.3389/fpls.2023.1234462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 08/07/2023] [Indexed: 09/16/2023]
Abstract
Investigation on intrinsic properties of photosynthetic pigment molecules participating in solar energy absorption and excitation, especially their eigen-absorption cross-section (σ ik) and effective absorption cross-section (σ ' ik), is important to understand photosynthesis. Here, we present the development and application of a new method to determine these parameters, based on a mechanistic model of the photosynthetic electron flow-light response. The analysis with our method of a series of previously collected chlorophyll a fluorescence data shows that the absorption cross-section of photosynthetic pigment molecules has different values of approximately 10-21 m2, for several photosynthetic organisms grown under various conditions: (1) the conifer Abies alba Mill., grown under high light or low light; (2) Taxus baccata L., grown under fertilization or non-fertilization conditions; (3) Glycine max L. (Merr.), grown under a CO2 concentration of 400 or 600 μmol CO2 mol-1 in a leaf chamber under shaded conditions; (4) Zea mays L., at temperatures of 30°C or 35°C in a leaf chamber; (5) Osmanthus fragrans Loureiro, with shaded-leaf or sun-leaf; and (6) the cyanobacterium Microcystis aeruginosa FACHB905, grown under two different nitrogen supplies. Our results show that σ ik has the same order of magnitude (approximately 10-21 m2), and σ ' ik for these species decreases with increasing light intensity, demonstrating the operation of a key regulatory mechanism to reduce solar absorption and avoid high light damage. Moreover, compared with other approaches, both σ ik and σ ' ik can be more easily estimated by our method, even under various growth conditions (e.g., different light environment; different CO2, NO2, O2, and O3 concentrations; air temperatures; or water stress), regardless of the type of the sample (e.g., dilute or concentrated cell suspensions or leaves). Our results also show that CO2 concentration and temperature have little effect on σ ik values for G. max and Z. mays. Consequently, our approach provides a powerful tool to investigate light energy absorption of photosynthetic pigment molecules and gives us new information on how plants and cyanobacteria modify their light-harvesting properties under different stress conditions.
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Affiliation(s)
- Zi-Piao Ye
- The Institute of Biophysics in College of Mathematics and Physics, Jinggangshan University, Ji’an, Jiangxi, China
| | | | - Ting An
- School of Biological Sciences and Engineering, Jiangxi Agriculture University, Nanchang, China
| | - Piotr Robakowski
- Faculty of Forestry and Wood Technology, Poznan University of Life Sciences, Poznan, Poland
| | - Hua-Jing Kang
- Southern Zhejiang Key Laboratory of Crop Breeding, Wenzhou Academy of Agricultural Sciences, Wenzhou, Zhejiang, China
| | - Xiao-Long Yang
- School of Life Sciences, Nantong University, Nantong, Jiangsu, China
| | - Fu-Biao Wang
- The Institute of Biophysics in College of Mathematics and Physics, Jinggangshan University, Ji’an, Jiangxi, China
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7
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Abstract
The theory of electron transfer reactions establishes the conceptual foundation for redox solution chemistry, electrochemistry, and bioenergetics. Electron and proton transfer across the cellular membrane provide all energy of life gained through natural photosynthesis and mitochondrial respiration. Rates of biological charge transfer set kinetic bottlenecks for biological energy storage. The main system-specific parameter determining the activation barrier for a single electron-transfer hop is the reorganization energy of the medium. Both harvesting of light energy in natural and artificial photosynthesis and efficient electron transport in biological energy chains require reduction of the reorganization energy to allow fast transitions. This review article discusses mechanisms by which small values of the reorganization energy are achieved in protein electron transfer and how similar mechanisms can operate in other media, such as nonpolar and ionic liquids. One of the major mechanisms of reorganization energy reduction is through non-Gibbsian (nonergodic) sampling of the medium configurations on the reaction time. A number of alternative mechanisms, such as electrowetting of active sites of proteins, give rise to non-parabolic free energy surfaces of electron transfer. These mechanisms, and nonequilibrium population of donor-acceptor vibrations, lead to a universal phenomenology of separation between the Stokes shift and variance reorganization energies of electron transfer.
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Affiliation(s)
- Dmitry V Matyushov
- School of Molecular Sciences and Department of Physics, Arizona State University, PO Box 871504, Tempe, Arizona 85287-1504, USA.
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8
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Samaei A, Deshmukh SS, Protheroe C, Nyéki S, Tremblay-Ethier RA, Kálmán L. Photoactivation and conformational gating for manganese binding and oxidation in bacterial reaction centers. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148928. [PMID: 36216075 DOI: 10.1016/j.bbabio.2022.148928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/26/2022] [Accepted: 10/03/2022] [Indexed: 11/05/2022]
Abstract
The influence of illumination history of native bacterial reaction centers (BRCs) on the ability of binding and photo-induced oxidation of manganous ions was investigated in the pH range between 8.0 and 9.4. Binding of manganous ions to a buried site required 6 to 11-fold longer incubation periods, depending on the pH, in dark-adapted BRCs than in BRCs that were previously illuminated prior to manganese binding. The intrinsic electron transfer from the bound manganese ion to the photo-oxidized primary electron donor was found to be limited by a 2 to 5-fold slower precursor conformational step in the dark-adapted samples for the same pH range. The conformational gating could be eliminated by photoactivation, namely if the BRCs were illuminated prior to binding. Unlike in Photosystem II, photoactivation in BRCs did not involve cluster assembly. Photoactivation with manganese already bound was only possible at elevated detergent concentration. In addition, also exclusively in dark-adapted BRCs, a marked breaking point in the Arrhenius-plot was discovered around 15 °C at pH 9.4 indicating a change in the reaction mechanism, most likely caused by the change of orientation of the 2-acetyl group of the inactive bacteriochlorophyll monomer located near the manganese binding site.
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Affiliation(s)
- Ali Samaei
- Department of Physics, Concordia University, Montreal, QC, Canada
| | | | | | - Sarah Nyéki
- Department of Physics, Concordia University, Montreal, QC, Canada
| | | | - László Kálmán
- Department of Physics, Concordia University, Montreal, QC, Canada.
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9
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Sarhangi SM, Matyushov DV. Theory of Protein Charge Transfer: Electron Transfer between Tryptophan Residue and Active Site of Azurin. J Phys Chem B 2022; 126:10360-10373. [PMID: 36459590 DOI: 10.1021/acs.jpcb.2c05258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
One reaction step in the conductivity relay of azurin, electron transfer between the Cu-based active site and the tryptophan residue, is studied theoretically and by classical molecular dynamics simulations. Oxidation of tryptophan results in electrowetting of this residue. This structural change makes the free energy surfaces of electron transfer nonparabolic as described by the Q-model of electron transfer. We analyze the medium dynamical effect on protein electron transfer produced by coupled Stokes-shift dynamics and the dynamics of the donor-acceptor distance modulating electron tunneling. The equilibrium donor-acceptor distance falls in the plateau region of the rate constant, where it is determined by the protein-water dynamics, and the probability of electron tunneling does not affect the rate. The crossover distance found here puts most intraprotein electron-transfer reactions under the umbrella of dynamical control. The crossover between the medium-controlled and tunneling-controlled kinetics is combined with the effect of the protein-water medium on the activation barrier to formulate principles of tunability of protein-based charge-transfer chains. The main principle in optimizing the activation barrier is the departure from the Gaussian-Gibbsian statistics of fluctuations promoting activated transitions. This is achieved either by incomplete (nonergodic) sampling, breaking the link between the Stokes-shift and variance reorganization energies, or through wetting-induced structural changes of the enzyme's active site.
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Affiliation(s)
- Setare Mostajabi Sarhangi
- School of Molecular Sciences and Department of Physics, Arizona State University, PO Box 871504, Tempe, Arizona85287-1504, United States
| | - Dmitry V Matyushov
- School of Molecular Sciences and Department of Physics, Arizona State University, PO Box 871504, Tempe, Arizona85287-1504, United States
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10
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Tian X, Xu X, Chen Y, Chen J, Xu WS. Explicit analytical form for memory kernel in the generalized Langevin equation for end-to-end vector of Rouse chains. J Chem Phys 2022; 157:224901. [PMID: 36546812 DOI: 10.1063/5.0124925] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The generalized Langevin equation (GLE) provides an attractive theoretical framework for investigating the dynamics of conformational fluctuations of polymeric systems. While the memory kernel is a central function in the GLE, explicit analytical forms for this function have been challenging to obtain, even for the simple models of polymer dynamics. Here, we achieve an explicit analytical expression for the memory kernel in the GLE for the end-to-end vector of Rouse chains in the overdamped limit. Our derivation takes advantage of the finding that the dynamics of the end-to-end vector of Rouse chains with both free ends are equivalent to those of Rouse chains with one free end and the other fixed. For the latter model, we first show that the equations of motion of the Rouse modes as well as their statistical properties can be obtained under the boundary conditions where the free end is held fixed temporarily. We then analytically solve the terms associated with intrachain interactions in the GLE. By formally comparing these terms with the GLE based on the Rouse modes, we obtain an explicit expression for the memory kernel, along with analytical forms for the potential field and the random colored noise force. Our analytical memory kernel is confirmed by numerical calculations in the Laplace space and is shown to yield asymptotic behaviors that are consistent with previous studies. Finally, we utilize our analytical result to simulate the cyclization dynamics of Rouse chains and discuss the scaling of the cyclization time with chain length.
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Affiliation(s)
- Xiaofei Tian
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China
| | - Xiaolei Xu
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China
| | - Ye Chen
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China
| | - Jizhong Chen
- School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Wen-Sheng Xu
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China
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11
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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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12
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Gao S, Klinman JP. Functional roles of enzyme dynamics in accelerating active site chemistry: Emerging techniques and changing concepts. Curr Opin Struct Biol 2022; 75:102434. [PMID: 35872562 PMCID: PMC9901422 DOI: 10.1016/j.sbi.2022.102434] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/15/2022] [Accepted: 06/21/2022] [Indexed: 02/08/2023]
Abstract
With the growing acceptance of the contribution of protein conformational ensembles to enzyme catalysis and regulation, research in the field of protein dynamics has shifted toward an understanding of the atomistic properties of protein dynamical networks and the mechanisms and time scales that control such behavior. A full description of an enzymatic reaction coordinate is expected to extend beyond the active site and include site-specific networks that communicate with the protein/water interface. Advances in experimental tools for the spatial resolution of thermal activation pathways are being complemented by biophysical methods for visualizing dynamics in real time. An emerging multidimensional model integrates the impacts of bound substrate/effector on the distribution of protein substates that are in rapid equilibration near room temperature with reaction-specific protein embedded heat transfer conduits.
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Affiliation(s)
- Shuaihua Gao
- Department of Chemistry, University of California, Berkeley, CA, 94720, United States; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, United States. https://twitter.com/S_H_Gao
| | - Judith P Klinman
- Department of Chemistry, University of California, Berkeley, CA, 94720, United States; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, United States; Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, United States.
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13
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Alachkar A. Aromatic patterns: Tryptophan aromaticity as a catalyst for the emergence of life and rise of consciousness. Phys Life Rev 2022; 42:93-114. [PMID: 35905538 DOI: 10.1016/j.plrev.2022.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 07/12/2022] [Indexed: 11/28/2022]
Abstract
Sunlight held the key to the origin of life on Earth. The earliest life forms, cyanobacteria, captured the sunlight to generate energy through photosynthesis. Life on Earth evolved in accordance with the circadian rhythms tied to sensitivity to sunlight patterns. A unique feature of cyanobacterial photosynthetic proteins and circadian rhythms' molecules, and later of nearly all photon-sensing molecules throughout evolution, is that the aromatic amino acid tryptophan (Trp) resides at the center of light-harvesting active sites. In this perspective, I review the literature and integrate evidence from different scientific fields to explore the role Trp plays in photon-sensing capabilities of living organisms through its resonance delocalization of π-electrons. The observations presented here are the product of apparently unrelated phenomena throughout evolution, but nevertheless share consistent patterns of photon-sensing by Trp-containing and Trp-derived molecules. I posit the unique capacity to transfer electrons during photosynthesis in the earliest life forms is conferred to Trp due to its aromaticity. I propose this ability evolved to assume more complex functions, serving as a host for mechanisms underlying mental aptitudes - a concept which provides a theoretical basis for defining the neural correlates of consciousness. The argument made here is that Trp aromaticity may have allowed for the inception of the mechanistic building blocks used to fabricate complexity in higher forms of life. More specifically, Trp aromatic non-locality may have acted as a catalyst for the emergence of consciousness by instigating long-range synchronization and stabilizing the large-scale coherence of neural networks, which mediate functional brain activity. The concepts proposed in this perspective provide a conceptual foundation that invites further interdisciplinary dialogue aimed at examining and defining the role of aromaticity (beyond Trp) in the emergence of life and consciousness.
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Affiliation(s)
- Amal Alachkar
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, CA 92697, USA; UC Irvine Center for the Neurobiology of Learning and Memory, University of California-Irvine, Irvine, CA 92697, USA; Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California, Irvine, CA 92697, USA.
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14
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Kundu P. Kinetics of Initial Charge Separation in the Photosynthetic Reaction Centers of Rhodobacter sphaeroides. J Phys Chem B 2022; 126:3470-3476. [PMID: 35522727 DOI: 10.1021/acs.jpcb.1c09809] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A stochastic kinetic study of the initial electron transfer reaction in the reaction centers of wild-type and different mutants of photosynthetic bacterium Rhodobacter sphaeroides is suggested. The present approach to the disorder-driven complex kinetics skilfully offers an alternative to the earlier dynamic analyses. Exploiting a rational description of the reaction coordinate, effected by the relaxation of the surrounding protein environment, the measured kinetics were reproduced quantitatively. Notably, comparisons of the extracted relative free energies of electron transfer for the selected mutants and the available independent electrochemical estimates show exact agreement in some cases.
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Affiliation(s)
- Prasanta Kundu
- S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
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15
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Yang J, Zhang Y, Lu Y, Wang L, Lu F, Zhong D. Ultrafast Dynamics of Nonequilibrium Short-Range Electron Transfer in Semiquinone Flavodoxin. J Phys Chem Lett 2022; 13:3202-3208. [PMID: 35377652 DOI: 10.1021/acs.jpclett.2c00057] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Short-range protein electron transfer (ET) is crucially important in light-induced biological processes such as in photoenzymes and photoreceptors and often occurs on time scales similar to those of environment fluctuations, leading to a coupled dynamic process. Herein, we use semiquinone Anabaena flavodoxin to characterize the ultrafast photoinduced redox cycle of the wild type and seven mutants by ultrafast spectroscopy. We have found that the forward and backward ET dynamics show stretched behaviors in a few picoseconds (1-5 ps), indicating a coupling with the local protein fluctuations. By comparison with the results from semiquinone D. vulgaris flavodoxin, we find that the electronic coupling is crucial to the ET rates. With our new nonergodic model, we obtain smaller values of the outer reorganization energy (λoγ) of environment fluctuations and the reaction free energy force (ΔGγ), a signature of nonequilibrium ET dynamics.
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Affiliation(s)
- Jie Yang
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yifei Zhang
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yangyi Lu
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lijuan Wang
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Faming Lu
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dongping Zhong
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
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16
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Selikhanov G, Fufina T, Guenther S, Meents A, Gabdulkhakov A, Vasilieva L. X-ray structure of the Rhodobacter sphaeroides reaction center with an M197 Phe→His substitution clarifies the properties of the mutant complex. IUCRJ 2022; 9:261-271. [PMID: 35371503 PMCID: PMC8895020 DOI: 10.1107/s2052252521013178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 12/11/2021] [Indexed: 06/14/2023]
Abstract
The first steps of the global process of photosynthesis take place in specialized membrane pigment-protein complexes called photosynthetic reaction centers (RCs). The RC of the photosynthetic purple bacterium Rhodobacter sphaeroides, a relatively simple analog of the more complexly organized photosystem II in plants, algae and cyanobacteria, serves as a convenient model for studying pigment-protein interactions that affect photochemical processes. In bacterial RCs the bacteriochlorophyll (BChl) dimer P serves as the primary electron donor, and its redox potential is a critical factor in the efficient functioning of the RC. It has previously been shown that the replacement of Phe M197 by His strongly affects the oxidation potential of P (E m P/P+), increasing its value by 125 mV, as well as increasing the thermal stability of RC and its stability in response to external pressure. The crystal structures of F(M197)H RC at high resolution obtained using various techniques presented in this report clarify the optical and electrochemical properties of the primary electron donor and the increased resistance of the mutant complex to denaturation. The electron-density maps are consistent with the donation of a hydrogen bond from the imidazole group of His M197 to the C2-acetyl carbonyl group of BChl PB. The formation of this hydrogen bond leads to a considerable out-of-plane rotation of the acetyl carbonyl group and results in a 1.2 Å shift of the O atom of this group relative to the wild-type structure. Besides, the distance between BChl PA and PB in the area of pyrrole ring I was found to be increased by up to 0.17 Å. These structural changes are discussed in association with the spectral properties of BChl dimer P. The electron-density maps strongly suggest that the imidazole group of His M197 accepts another hydrogen bond from the nearest water molecule, which in turn appears to form two more hydrogen bonds to Asn M195 and Asp L155. As a result of the F(M197)H mutation, BChl PB finds itself connected to the extensive hydrogen-bonding network that pre-existed in wild-type RC. Dissimilarities in the two hydrogen-bonding networks near the M197 and L168 sites may account for the different changes of the E m P/P+ in F(M197)H and H(L168)F RCs. The involvement of His M197 in the hydrogen-bonding network also appears to be related to stabilization of the F(M197)H RC structure. Analysis of the experimental data presented here and of the data available in the literature points to the fact that the hydrogen-bonding networks in the vicinity of BChl dimer P may play an important role in fine-tuning the redox properties of the primary electron donor.
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Affiliation(s)
- Georgii Selikhanov
- Group of Structural Studies of Macromolecular Complexes, Institute of Protein Research, Russian Academy of Sciences, Institutskaya 4, Pushchino 142290, Moscow Region, Russian Federation
- Federal Research Center Pushchino Scientific Center for Biological Research PSCBR, Institute of Basic Biological Problems, Russian Academy of Sciences, Institutskaya 2, Pushchino 142290, Moscow Region, Russian Federation
| | - Tatiana Fufina
- Federal Research Center Pushchino Scientific Center for Biological Research PSCBR, Institute of Basic Biological Problems, Russian Academy of Sciences, Institutskaya 2, Pushchino 142290, Moscow Region, Russian Federation
| | - Sebastian Guenther
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Alke Meents
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Azat Gabdulkhakov
- Group of Structural Studies of Macromolecular Complexes, Institute of Protein Research, Russian Academy of Sciences, Institutskaya 4, Pushchino 142290, Moscow Region, Russian Federation
| | - Lyudmila Vasilieva
- Federal Research Center Pushchino Scientific Center for Biological Research PSCBR, Institute of Basic Biological Problems, Russian Academy of Sciences, Institutskaya 2, Pushchino 142290, Moscow Region, Russian Federation
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17
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Kondo T, Mutoh R, Arai S, kurisu G, Oh-oka H, Fujiyoshi S, Matsushita M. Energy transfer fluctuation observed by single-molecule spectroscopy of red-shifted bacteriochlorophyll in the homodimeric photosynthetic reaction center. J Chem Phys 2022; 156:105102. [DOI: 10.1063/5.0077290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Toru Kondo
- Department of Life Science and Technology, Tokyo Institute of Technology, Japan
| | | | - Shun Arai
- Tokyo Institute of Technology, Japan
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18
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Yang J, Zhang Y, He TF, Lu Y, Wang L, Ding B, Zhong D. Ultrafast nonequilibrium dynamics of short-range protein electron transfer in flavodoxin. Phys Chem Chem Phys 2021; 24:382-391. [PMID: 34889914 DOI: 10.1039/d1cp04445a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Short-range protein electron transfer (ET) is ubiquitous in biology and is often observed in photosynthesis, photoreceptors and photoenzymes. These ET processes occur on an ultrafast timescale from femtoseconds to picoseconds at a short donor-acceptor distance within 10 Å, and thus couple with local environmental fluctuations. Here, we use oxidized Anabaena flavodoxin as a model system and have systematically studied the photoinduced redox cycle of the wild type and seven mutant proteins by femtosecond spectroscopy. We observed a series of ultrafast dynamics from the initial charge separation in 100-200 fs, subsequent charge recombination in 1-2 ps and final vibrational cooling process of the products in 3-6 ps. We further characterized the active-site solvation and observed the relaxations in 1-200 ps, indicating a nonergodic ET dynamics. With our new ET model, we uncovered a minor outer (solvent) reorganization energy and a large inner (donor and acceptor) reorganization energy, suggesting a frozen active site in the initial ultrafast ET while the back ET couples with the environment relaxations. The vibronically coupled back ET dynamics was first reported in D. vulgaris flavodoxin and here is observed in Anabaena flavodoxin again, completely due to the faster ET dynamics than the cooling relaxations. We also compared the two flavodoxin structures, revealing a stronger coupling with the donor tyrosine in Anabaena. All ultrafast ET dynamics are from the large donor-acceptor couplings and the minor activation barriers due to the reaction free energies being close to the inner reorganization energies. These observations should be general to many redox reactions in flavoproteins.
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Affiliation(s)
- Jie Yang
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Yifei Zhang
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Ting-Fang He
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | - Yangyi Lu
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Lijuan Wang
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | - Bei Ding
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Dongping Zhong
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China. .,Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
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19
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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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20
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Abstract
We present the first exact solution to the time-independent Schrödinger equation of a model Hamiltonian consisting of a vibrational mode coupled to three electronic states. This Hamiltonian serves as a generic model for photo-induced electronic transfer reactions. The solution is non-perturbative and can be applied to ET reactions with weak and strong electronic and vibrational coupling strengths. This work suggests a new direction towards understanding the vibronic effects in ET dynamics beyond the non-adiabatic limit and Condon approximation.
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Affiliation(s)
- Yangyi Lu
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States.,Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Dongping Zhong
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States.,Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
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21
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Kang DH, Kim J, Kim SK. Recapture of the Nonvalence Excess Electron into the Excited Valence Orbital Leads to the Chemical Bond Cleavage in the Anion. J Phys Chem Lett 2021; 12:6383-6388. [PMID: 34232669 DOI: 10.1021/acs.jpclett.1c01789] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The excess electron in the dipole-bound state (DBS) of the anion is found to be recaptured into the excited valence orbital localized at the positive end of the dipole, leading to the chemical bond cleavage of the anion. In the DBS of the 4-iodophenoxide anion, the extremely loosely bound electron (binding energy of 53 cm-1) is recaptured into the πσ* valence orbital, which is repulsive along the C-I bond extension coordinate, leading to the iodide (I-) and phenoxyl diradical (·C6H4O·) channel at the asymptotic limit. This is the first real-time observation of the state-specific relaxation (other than autodetachment) dynamics of the DBS and subsequent chemical reaction. The lifetime of the 4-iodophenoxide DBS at its zero-point energy (ZPE), which is measured for the cryogenically cooled trapped anion using the picosecond laser pump-probe scheme, has been estimated to be ∼9.5 ± 0.3 ps. Quantum mechanical calculations support the efficient transition from the DBS (below the detachment threshold) to the low-lying πσ* valence orbital of the first excited state of the anion. Similar experiments on 4-chlorophenoxide and 4-bromophenoxide anions indicate that the electron recaptures into excited valence orbitals hardly occur in the DBS of those anions, giving the long lifetimes (≫ns) at ZPE, suggesting that the internal conversion to S0 may be the major relaxation pathway for those anions.
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Affiliation(s)
- Do Hyung Kang
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Jinwoo Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
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22
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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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23
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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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24
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Magdaong NCM, Buhrmaster JC, Faries KM, Liu H, Tira GA, Lindsey JS, Hanson DK, Holten D, Laible PD, Kirmaier C. In Situ, Protein-Mediated Generation of a Photochemically Active Chlorophyll Analogue in a Mutant Bacterial Photosynthetic Reaction Center. Biochemistry 2021; 60:1260-1275. [PMID: 33835797 DOI: 10.1021/acs.biochem.1c00137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
All possible natural amino acids have been substituted for the native LeuL185 positioned near the B-side bacteriopheophytin (HB) in the bacterial reaction center (RC) from Rhodobacter sphaeroides. Additional mutations that enhance electron transfer to the normally inactive B-side cofactors are present. Approximately half of the isolated RCs with Glu at L185 contain a magnesium chlorin (CB) in place of HB. The chlorin is not the common BChl a oxidation product 3-desvinyl-3-acetyl chlorophyll a with a C-C bond in ring D and a C═C bond in ring B but has properties consistent with reversal of these bond orders, giving 17,18-didehydro BChl a. In such RCs, charge-separated state P+CB- forms in ∼5% yield. The other half of the GluL185-containing RCs have a bacteriochlorophyll a (BChl a) denoted βB in place of HB. Residues His, Asp, Asn, and Gln at L185 yield RCs with ≥85% βB in the HB site, while most other amino acids result in RCs that retain HB (≥95%). To the best of our knowledge, neither bacterial RCs that harbor five BChl a molecules and one chlorophyll analogue nor those with six BChl a molecules have been reported previously. The finding that altering the local environment within a cofactor binding site of a transmembrane complex leads to in situ generation of a photoactive chlorin with an unusual ring oxidation pattern suggests new strategies for amino acid control over pigment type at specific sites in photosynthetic proteins.
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Affiliation(s)
- Nikki Cecil M Magdaong
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - James C Buhrmaster
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Kaitlyn M Faries
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Haijun Liu
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Gregory A Tira
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Jonathan S Lindsey
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Deborah K Hanson
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Dewey Holten
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Philip D Laible
- Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Christine Kirmaier
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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25
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Ultrafast structural changes within a photosynthetic reaction centre. Nature 2021; 589:310-314. [PMID: 33268896 DOI: 10.1038/s41586-020-3000-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 09/28/2020] [Indexed: 01/29/2023]
Abstract
Photosynthetic reaction centres harvest the energy content of sunlight by transporting electrons across an energy-transducing biological membrane. Here we use time-resolved serial femtosecond crystallography1 using an X-ray free-electron laser2 to observe light-induced structural changes in the photosynthetic reaction centre of Blastochloris viridis on a timescale of picoseconds. Structural perturbations first occur at the special pair of chlorophyll molecules of the photosynthetic reaction centre that are photo-oxidized by light. Electron transfer to the menaquinone acceptor on the opposite side of the membrane induces a movement of this cofactor together with lower amplitude protein rearrangements. These observations reveal how proteins use conformational dynamics to stabilize the charge-separation steps of electron-transfer reactions.
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26
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Fraggedakis D, McEldrew M, Smith RB, Krishnan Y, Zhang Y, Bai P, Chueh WC, Shao-Horn Y, Bazant MZ. Theory of coupled ion-electron transfer kinetics. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2020.137432] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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Gorka M, Cherepanov DA, Semenov AY, Golbeck JH. Control of electron transfer by protein dynamics in photosynthetic reaction centers. Crit Rev Biochem Mol Biol 2020; 55:425-468. [PMID: 32883115 DOI: 10.1080/10409238.2020.1810623] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Trehalose and glycerol are low molecular mass sugars/polyols that have found widespread use in the protection of native protein states, in both short- and long-term storage of biological materials, and as a means of understanding protein dynamics. These myriad uses are often attributed to their ability to form an amorphous glassy matrix. In glycerol, the glass is formed only at cryogenic temperatures, while in trehalose, the glass is formed at room temperature, but only upon dehydration of the sample. While much work has been carried out to elucidate a mechanistic view of how each of these matrices interact with proteins to provide stability, rarely have the effects of these two independent systems been directly compared to each other. This review aims to compile decades of research on how different glassy matrices affect two types of photosynthetic proteins: (i) the Type II bacterial reaction center from Rhodobacter sphaeroides and (ii) the Type I Photosystem I reaction center from cyanobacteria. By comparing aggregate data on electron transfer, protein structure, and protein dynamics, it appears that the effects of these two distinct matrices are remarkably similar. Both seem to cause a "tightening" of the solvation shell when in a glassy state, resulting in severely restricted conformational mobility of the protein and associated water molecules. Thus, trehalose appears to be able to mimic, at room temperature, nearly all of the effects on protein dynamics observed in low temperature glycerol glasses.
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Affiliation(s)
- Michael Gorka
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, USA
| | - Dmitry A Cherepanov
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, Russia.,A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Alexey Yu Semenov
- N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, Russia.,A.N. Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, USA.,Department of Chemistry, The Pennsylvania State University, University Park, PA, USA
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28
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Lu Y, Kundu M, Zhong D. Effects of nonequilibrium fluctuations on ultrafast short-range electron transfer dynamics. Nat Commun 2020; 11:2822. [PMID: 32499536 PMCID: PMC7272615 DOI: 10.1038/s41467-020-15535-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 03/16/2020] [Indexed: 01/10/2023] Open
Abstract
A variety of electron transfer (ET) reactions in biological systems occurs at short distances and is ultrafast. Many of them show behaviors that deviate from the predictions of the classic Marcus theory. Here, we show that these ultrafast ET dynamics highly depend on the coupling between environmental fluctuations and ET reactions. We introduce a dynamic factor, γ (0 ≤ γ ≤ 1), to describe such coupling, with 0 referring to the system without coupling to a “frozen” environment, and 1 referring to the system’s complete coupling with the environment. Significantly, this system’s coupling with the environment modifies the reaction free energy, ΔGγ, and the reorganization energy, λγ, both of which become smaller. This new model explains the recent ultrafast dynamics in flavodoxin and elucidates the fundamental mechanism of nonequilibrium ET dynamics, which is critical to uncovering the molecular nature of many biological functions. Ultrafast electron-transfer reactions are fundamental to protein functions. Here the authors show that these reaction dynamics are affected by the ruggedness of protein energy landscape, which even modifies the reaction free energy and reorganization energy.
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Affiliation(s)
- Yangyi Lu
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, OH, 43210, USA
| | - Mainak Kundu
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, OH, 43210, USA
| | - Dongping Zhong
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, OH, 43210, USA. .,Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, 200240, Shanghai, China.
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29
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Kondo T, Mutoh R, Tabe H, Kurisu G, Oh-Oka H, Fujiyoshi S, Matsushita M. Cryogenic Single-Molecule Spectroscopy of the Primary Electron Acceptor in the Photosynthetic Reaction Center. J Phys Chem Lett 2020; 11:3980-3986. [PMID: 32352789 DOI: 10.1021/acs.jpclett.0c00891] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The photosynthetic reaction center (RC) converts light energy into electrochemical energy. The RC of heliobacteria (hRC) is a primitive homodimeric RC containing 58 bacteriochlorophylls and 2 chlorophyll as. The chlorophyll serves as the primary electron acceptor (Chl a-A0) responsible for light harvesting and charge separation. The single-molecule spectroscopy of Chl a-A0 can be used to investigate heterogeneities of the RC photochemical function, though the low fluorescence quantum yield (0.1%) makes it difficult. Here, we show the fluorescence excitation spectroscopy of individual Chl a-A0s in single hRCs at 6 K. The fluorescence quantum yield and absorption cross section of Chl a-A0 increase 2- and 4-fold, respectively, compared to those at room temperature. The two Chl a-A0s in single hRCs are identified as two distinct peaks in the fluorescence excitation spectrum, exhibiting different excitation polarization dependences. The spectral changes caused by photobleaching indicate the energy transfer across subunits in the hRC.
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Affiliation(s)
- Toru Kondo
- Department of Physics, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
| | - Risa Mutoh
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hiroaki Tabe
- Department of Physics, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
| | - Genji Kurisu
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hirozo Oh-Oka
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Satoru Fujiyoshi
- Department of Physics, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
| | - Michio Matsushita
- Department of Physics, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
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30
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Ostroumov EE, Götze JP, Reus M, Lambrev PH, Holzwarth AR. Characterization of fluorescent chlorophyll charge-transfer states as intermediates in the excited state quenching of light-harvesting complex II. PHOTOSYNTHESIS RESEARCH 2020; 144:171-193. [PMID: 32307623 DOI: 10.1007/s11120-020-00745-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 03/31/2020] [Indexed: 05/20/2023]
Abstract
Light-harvesting complex II (LHCII) is the major antenna complex in higher plants and green algae. It has been suggested that a major part of the excited state energy dissipation in the so-called "non-photochemical quenching" (NPQ) is located in this antenna complex. We have performed an ultrafast kinetics study of the low-energy fluorescent states related to quenching in LHCII in both aggregated and the crystalline form. In both sample types the chlorophyll (Chl) excited states of LHCII are strongly quenched in a similar fashion. Quenching is accompanied by the appearance of new far-red (FR) fluorescence bands from energetically low-lying Chl excited states. The kinetics of quenching, its temperature dependence down to 4 K, and the properties of the FR-emitting states are very similar both in LHCII aggregates and in the crystal. No such FR-emitting states are found in unquenched trimeric LHCII. We conclude that these states represent weakly emitting Chl-Chl charge-transfer (CT) states, whose formation is part of the quenching process. Quantum chemical calculations of the lowest energy exciton and CT states, explicitly including the coupling to the specific protein environment, provide detailed insight into the chemical nature of the CT states and the mechanism of CT quenching. The experimental data combined with the results of the calculations strongly suggest that the quenching mechanism consists of a sequence of two proton-coupled electron transfer steps involving the three quenching center Chls 610/611/612. The FR-emitting CT states are reaction intermediates in this sequence. The polarity-controlled internal reprotonation of the E175/K179 aa pair is suggested as the switch controlling quenching. A unified model is proposed that is able to explain all known conditions of quenching or non-quenching of LHCII, depending on the environment without invoking any major conformational changes of the protein.
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Affiliation(s)
- Evgeny E Ostroumov
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470, Mülheim a. d. Ruhr, Germany
- Quantum Matter Institute, University of British Columbia, 2355 East Mall, Vancouver, V6T 1Z1, Canada
| | - Jan P Götze
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470, Mülheim a. d. Ruhr, Germany
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, 14195, Berlin, Germany
| | - Michael Reus
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470, Mülheim a. d. Ruhr, Germany
| | - Petar H Lambrev
- Biological Research Centre, Temesvári krt. 62, Szeged, 6726, Hungary
| | - Alfred R Holzwarth
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470, Mülheim a. d. Ruhr, Germany.
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31
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Kundu P, Saha S, Gangopadhyay G. Mechanical Unfolding of Single Polyubiquitin Molecules Reveals Evidence of Dynamic Disorder. ACS OMEGA 2020; 5:9104-9113. [PMID: 32363262 PMCID: PMC7191566 DOI: 10.1021/acsomega.9b03701] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 03/09/2020] [Indexed: 06/11/2023]
Abstract
Mechanical unfolding of single polyubiquitin molecules subjected to a constant stretching force showed nonexponentiality in the measured probability density of unfolding (waiting time distribution) and the survival probability of the folded state during the course of the measurements. These observations explored the relevance of disorder present in the system under study with implications for a static disorder approach to rationalize the experimental results. Here, an approach for dynamic disorder is presented based on Zwanzig's fluctuating bottleneck (FB) model, in which the rate of the reaction is controlled by the passage through the cross-sectional area of the bottleneck. The radius of the latter undergoes stochastic fluctuations that in turn is described in terms of the end-to-end distance fluctuations of the Rouse-like dynamics using a non-Markovian generalized Langevin equation with a memory kernel and Gaussian colored noise. Our results are comprised of analytical expressions for the survival probability and waiting time distribution, which show excellent agreement with the experimental data throughout the range of the applied forces. In addition, by fitting the survival probabilities at different stretching forces, we quantify two system parameters, namely, the average free energy ΔG av and the average distance to the transition state Δx av, both perfectly recovered the experimental estimates. These agreements validate the present model of polymer dynamics, which captures the very essence of dynamic disorder in single-molecule pulling experiments.
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Affiliation(s)
- Prasanta Kundu
- S.
N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
| | - Soma Saha
- Department
of Chemistry, Presidency University, 86/1 College Street, Kolkata 700073, India
| | - Gautam Gangopadhyay
- S.
N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
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32
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Wickstrand C, Katona G, Nakane T, Nogly P, Standfuss J, Nango E, Neutze R. A tool for visualizing protein motions in time-resolved crystallography. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2020; 7:024701. [PMID: 32266303 PMCID: PMC7113034 DOI: 10.1063/1.5126921] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 03/06/2020] [Indexed: 05/12/2023]
Abstract
Time-resolved serial femtosecond crystallography (TR-SFX) at an x-ray free electron laser enables protein structural changes to be imaged on time-scales from femtoseconds to seconds. It can, however, be difficult to grasp the nature and timescale of global protein motions when structural changes are not isolated near a single active site. New tools are, therefore, needed to represent the global nature of electron density changes and their correlation with modeled protein structural changes. Here, we use TR-SFX data from bacteriorhodopsin to develop and validate a method for quantifying time-dependent electron density changes and correlating them throughout the protein. We define a spherical volume of difference electron density about selected atoms, average separately the positive and negative electron difference densities within each volume, and walk this spherical volume through all atoms within the protein. By correlating the resulting difference electron density amplitudes with time, our approach facilitates an initial assessment of the number and timescale of structural intermediates and highlights quake-like motions on the sub-picosecond timescale. This tool also allows structural models to be compared with experimental data using theoretical difference electron density changes calculated from refined resting and photo-activated structures.
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Affiliation(s)
- Cecilia Wickstrand
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530 Gothenburg, Sweden
| | - Gergely Katona
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530 Gothenburg, Sweden
| | | | - Przemyslaw Nogly
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zürich, Switzerland
| | - Joerg Standfuss
- Laboratory of Biomolecular Research, Department of Biology and Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | | | - Richard Neutze
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, SE-40530 Gothenburg, Sweden
- Author to whom correspondence should be addressed:
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33
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Rasheed F, Markgren J, Hedenqvist M, Johansson E. Modeling to Understand Plant Protein Structure-Function Relationships-Implications for Seed Storage Proteins. Molecules 2020; 25:E873. [PMID: 32079172 PMCID: PMC7071054 DOI: 10.3390/molecules25040873] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 02/13/2020] [Accepted: 02/14/2020] [Indexed: 11/30/2022] Open
Abstract
Proteins are among the most important molecules on Earth. Their structure and aggregation behavior are key to their functionality in living organisms and in protein-rich products. Innovations, such as increased computer size and power, together with novel simulation tools have improved our understanding of protein structure-function relationships. This review focuses on various proteins present in plants and modeling tools that can be applied to better understand protein structures and their relationship to functionality, with particular emphasis on plant storage proteins. Modeling of plant proteins is increasing, but less than 9% of deposits in the Research Collaboratory for Structural Bioinformatics Protein Data Bank come from plant proteins. Although, similar tools are applied as in other proteins, modeling of plant proteins is lagging behind and innovative methods are rarely used. Molecular dynamics and molecular docking are commonly used to evaluate differences in forms or mutants, and the impact on functionality. Modeling tools have also been used to describe the photosynthetic machinery and its electron transfer reactions. Storage proteins, especially in large and intrinsically disordered prolamins and glutelins, have been significantly less well-described using modeling. These proteins aggregate during processing and form large polymers that correlate with functionality. The resulting structure-function relationships are important for processed storage proteins, so modeling and simulation studies, using up-to-date models, algorithms, and computer tools are essential for obtaining a better understanding of these relationships.
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Affiliation(s)
- Faiza Rasheed
- Department of Plant Breeding, The Swedish University of Agricultural Sciences, Box 101, SE-230 53 Alnarp, Sweden; (F.R.); (J.M.)
- School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH Royal Institute of Technology, SE–100 44 Stockholm, Sweden;
| | - Joel Markgren
- Department of Plant Breeding, The Swedish University of Agricultural Sciences, Box 101, SE-230 53 Alnarp, Sweden; (F.R.); (J.M.)
| | - Mikael Hedenqvist
- School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH Royal Institute of Technology, SE–100 44 Stockholm, Sweden;
| | - Eva Johansson
- Department of Plant Breeding, The Swedish University of Agricultural Sciences, Box 101, SE-230 53 Alnarp, Sweden; (F.R.); (J.M.)
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34
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Lu Y, Zhong D. Nonequilibrium dynamics of photoinduced forward and backward electron transfer reactions. J Chem Phys 2020; 152:065102. [PMID: 32061242 DOI: 10.1063/1.5132814] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The biological functions of photoenzymes are often triggered by photoinduced electron transfer (ET) reactions. An ultrafast backward ET (BET) reaction follows the initial photoinduced forward ET (FET), which dissipates the energy of absorbed photons and terminates the biological function in vain. Based upon our previous works, we reasoned that the dynamics of the BET is coupled with that of the FET and other local motions. In this work, the dynamics of the FET and BET is modeled as the master equation of the reduced density operator of a three-state system coupled with a classical harmonic reservoir. The coupling of the FET and BET is reflected in the time-evolution of the charge-transfer state's population, which is generated by a source, the reaction flux for the FET, and annihilated by a sink, the reaction flux for the BET. Surprisingly, numerical simulations show that when the BET is in the Marcus normal region, the BET can be accelerated by nonequilibrium local motions and becomes faster than what is predicted by the Marcus theory. The experimental confirmation of this novel dynamics would provide qualitative evidence for nonequilibrium effects on ultrafast ET dynamics. Additionally, the effects of quantum vibrational modes on the dynamics are discussed. This work can help understand the dynamical interactions between the chain of ultrafast reactions and the complex local environmental motions, revealing the physical nature underlying biological functions.
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Affiliation(s)
- Yangyi Lu
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | - Dongping Zhong
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
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35
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Jalviste E, Timpmann K, Chenchiliyan M, Kangur L, Jones MR, Freiberg A. High-Pressure Modulation of Primary Photosynthetic Reactions. J Phys Chem B 2020; 124:718-726. [PMID: 31917566 DOI: 10.1021/acs.jpcb.9b09342] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photochemical charge separation is key to biological solar energy conversion. Although many features of this highly quantum-efficient process have been described, others remain poorly understood. Herein, ultrafast fluorescence barospectroscopy is used for the first time to obtain insights into the mechanism of primary charge separation in a YM210W mutant bacterial reaction center under novel surrounding modulating conditions. Over a range of applied hydrostatic pressures reaching 10 kbar, the rate of primary charge separation monotonously increased and that of the electron transfer to secondary acceptor decreased. While the inferred free energy gap for charge separation generally narrowed with increasing pressure, a pressure-induced break of a protein-cofactor hydrogen bond observed at ∼2 kbar significantly (by 219 cm-1 or 27 meV) increased this gap, resulting in a drop in fluorescence. The findings strongly favor a model for primary charge separation that incorporates charge recombination and restoration of the excited primary pair state, over a purely sequential model. We show that the main reason for the almost threefold acceleration of the primary electron transfer rate is the pressure-induced increase of the electronic coupling energy, rather than a change of activation energy. We also conclude that across all applied pressures, the primary electron transfer in the mutant reaction center studied can be considered nonadiabatic, normal region, and thermally activated.
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Affiliation(s)
- Erko Jalviste
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Kõu Timpmann
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Manoop Chenchiliyan
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Liina Kangur
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia
| | - Michael R Jones
- School of Biochemistry , University of Bristol , Biomedical Sciences Building, University Walk , Bristol BS8 1TD , U.K
| | - Arvi Freiberg
- Institute of Physics , University of Tartu , W. Ostwald Str. 1 , Tartu 50411 , Estonia.,Institute of Molecular and Cell Biology , University of Tartu , Riia 23 , Tartu 51010 , Estonia.,Estonian Academy of Sciences , Kohtu 6 , 10130 Tallinn , Estonia
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36
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Pospíšil P, Sýkora J, Takematsu K, Hof M, Gray HB, Vlček A. Light-Induced Nanosecond Relaxation Dynamics of Rhenium-Labeled Pseudomonas aeruginosa Azurins. J Phys Chem B 2020; 124:788-797. [PMID: 31935093 DOI: 10.1021/acs.jpcb.9b10802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Time-resolved phosphorescence spectra of Re(CO)3(dmp)+ and Re(CO)3(phen)+ chromophores (dmp = 4,7-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline) bound to surface histidines (H83, H124, and H126) of Pseudomonas aeruginosa azurin mutants exhibit dynamic band maxima shifts to lower wavenumbers following 3-exponential kinetics with 1-5 and 20-100 ns major phases and a 1.1-2.5 μs minor (5-16%) phase. Observation of slow relaxation components was made possible by using an organometallic Re chromophore as a probe whose long phosphorescence lifetime extends the observation window up to ∼3 μs. Integrated emission-band areas also decay with 2- or 3-exponential kinetics; the faster decay phase(s) is relaxation-related, whereas the slowest one [360-680 ns (dmp); 90-140 ns (phen)] arises mainly from population decay. As a result of shifting bands, the emission intensity decay kinetics depend on the detection wavelength. Detailed kinetics analyses and comparisons with band-shift dynamics are needed to disentangle relaxation and population decay kinetics if they occur on comparable timescales. The dynamic phosphorescence Stokes shift in Re-azurins is caused by relaxation motions of the solvent, the protein, and solvated amino acid side chains at the Re binding site in response to chromophore electronic excitation. Comparing relaxation and decay kinetics of Re(dmp)124K122CuII and Re(dmp)124W122CuII suggests that electron transfer (ET) and relaxation motions in the W122 mutant are coupled. It follows that nanosecond and faster photo-induced ET steps in azurins (and likely other redox proteins) occur from unrelaxed systems; importantly, these reactions can be driven (or hindered) by structural and solvational dynamics.
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Affiliation(s)
- Petr Pospíšil
- J. Heyrovský Institute of Physical Chemistry , Czech Academy of Sciences , Dolejškova 3 , CZ-182 23 Prague , Czech Republic
| | - Jan Sýkora
- J. Heyrovský Institute of Physical Chemistry , Czech Academy of Sciences , Dolejškova 3 , CZ-182 23 Prague , Czech Republic
| | - Kana Takematsu
- Department of Chemistry , Bowdoin College , Brunswick , Maine 04011 , United States
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry , Czech Academy of Sciences , Dolejškova 3 , CZ-182 23 Prague , Czech Republic
| | - Harry B Gray
- Beckman Institute , California Institute of Technology , Pasadena , California 91125 , United States
| | - Antonín Vlček
- J. Heyrovský Institute of Physical Chemistry , Czech Academy of Sciences , Dolejškova 3 , CZ-182 23 Prague , Czech Republic.,School of Biological and Chemical Sciences , Queen Mary University of London , Mile End Road , E1 4NS London , U.K
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37
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Brizhik LS, Luo J, Piette BMAG, Zakrzewski WJ. Long-range donor-acceptor electron transport mediated by α helices. Phys Rev E 2020; 100:062205. [PMID: 31962511 DOI: 10.1103/physreve.100.062205] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Indexed: 11/07/2022]
Abstract
We study the long-range electron and energy transfer mediated by a polaron on an α-helix polypeptide chain coupled to donor and acceptor molecules at opposite ends of the chain. We show that for specific parameters of the system, an electron initially located on the donor can tunnel onto the α helix, forming a polaron, which then travels to the other extremity of the polypeptide chain, where it is captured by the acceptor. We consider three families of couplings between the donor, the acceptor, and the chain and show that one of them can lead to a 90% efficiency of the electron transport from donor to acceptor. We also show that this process remains stable at physiological temperatures in the presence of thermal fluctuations in the system.
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Affiliation(s)
- L S Brizhik
- Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine
| | - J Luo
- School of Mathematics, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - B M A G Piette
- Department of Mathematical Sciences, University of Durham, Durham DH1 3LE, United Kingdom
| | - W J Zakrzewski
- Department of Mathematical Sciences, University of Durham, Durham DH1 3LE, United Kingdom
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38
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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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Khmelnitskiy A, Williams JC, Allen JP, Jankowiak R. Influence of Hydrogen Bonds on the Electron-Phonon Coupling Strength/Marker Mode Structure and Charge Separation Rates in Reaction Centers from Rhodobacter sphaeroides. J Phys Chem B 2019; 123:8717-8726. [PMID: 31539255 DOI: 10.1021/acs.jpcb.9b08388] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Low-temperature persistent and transient hole-burning (HB) spectra are presented for the triple hydrogen-bonded L131LH + M160LH + M197FH mutant of Rhodobacter sphaeroides. These spectra expose the heterogeneous nature of the P-, B-, and H-bands, consistent with a distribution of electron transfer (ET) times and excitation energy transfer (EET) rates. Transient P+QA- holes are observed for fast (tens of picoseconds or faster) ET times and reveal strong coupling to phonons and marker mode(s), while the persistent holes are bleached in a fraction of reaction centers with long-lived excited states characterized by much weaker electron-phonon coupling. Exposed differences in electron-phonon coupling strength, as well as a different coupling to the marker mode(s), appear to affect the ET times. Both resonantly and nonresonantly burned persistent HB spectra show weak blue- (∼150 cm-1) and large, red-shifted (∼300 cm-1) antiholes of the P band. Slower EET times from the H- and B-bands to the special pair dimer provide new insight on the influence of hydrogen bonds on mutation-induced heterogeneity.
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Affiliation(s)
| | - JoAnn C Williams
- School of Molecular Sciences , Arizona State University , Tempe , Arizona 85287 , United States
| | - James P Allen
- School of Molecular Sciences , Arizona State University , Tempe , Arizona 85287 , 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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41
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Bimolecular photoinduced electron transfer between 7-methylbenzo[a]pyrene and aromatic amine donors in stationary and static regimes. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2019.03.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Short-range electron-transfer (ET) reactions in biological systems are usually ultrafast, having transfer rates comparable to or even faster than corresponding environmental fluctuations, and often display nonexponential behaviors. To understand these nonequilibrium ET dynamics, we carried out detailed theoretical analyses based on the Sumi-Marcus model. It is shown that the ET dynamics is largely determined by the relative time scales of the ET reaction and its surrounding motions. Significantly, different environmental fluctuations can produce a variety of apparent ET dynamics even with the same driving force, Δ Go, and reorganization energy, λ. We applied our analyses to an ultrafast ET process in DNA repair by (6-4) photolyase and directly obtained the inner and outer reorganization energies (λi and λo) as well as the free energy Δ Go of various mutants, providing mechanical insight into ultrafast short-range ET reactions in proteins.
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Affiliation(s)
- Yangyi Lu
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Dongping Zhong
- Department of Physics, Department of Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
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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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Fujihashi Y, Higashi M, Ishizaki A. Intramolecular Vibrations Complement the Robustness of Primary Charge Separation in a Dimer Model of the Photosystem II Reaction Center. J Phys Chem Lett 2018; 9:4921-4929. [PMID: 30095266 DOI: 10.1021/acs.jpclett.8b02119] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The energy conversion of oxygenic photosynthesis is triggered by primary charge separation in proteins at the photosystem II reaction center. Here, we investigate the impacts of the protein environment and intramolecular vibrations on primary charge separation at the photosystem II reaction center. This is accomplished by combining the quantum dynamic theories of condensed phase electron transfer with quantum chemical calculations to evaluate the vibrational Huang-Rhys factors of chlorophyll and pheophytin molecules. We report that individual vibrational modes play a minor role in promoting charge separation, contrary to the discussion in recent publications. Nevertheless, these small contributions accumulate to considerably influence the charge separation rate, resulting in subpicosecond charge separation almost independent of the driving force and temperature. We suggest that the intramolecular vibrations complement the robustness of the charge separation in the photosystem II reaction center against the inherently large static disorder of the involved electronic energies.
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Affiliation(s)
- Yuta Fujihashi
- Institute for Molecular Science , National Institutes of Natural Sciences , Okazaki 444-8585 , Japan
| | - Masahiro Higashi
- Department of Chemistry, Biology, and Marine Science , University of the Ryukyus , 1 Senbaru , Nishihara , Okinawa 903-0213 , Japan
| | - Akihito Ishizaki
- Institute for Molecular Science , National Institutes of Natural Sciences , Okazaki 444-8585 , Japan
- School of Physical Sciences , The Graduate University for Advanced Studies , Okazaki 444-8585 , Japan
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Chen HW, Mallick S, Zou SF, Meng M, Liu CY. Mapping Bridge Conformational Effects on Electronic Coupling in Mo 2-Mo 2 Mixed-Valence Systems. Inorg Chem 2018; 57:7455-7467. [PMID: 29809000 DOI: 10.1021/acs.inorgchem.8b01056] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The large bridging ligand 9,10-anthracenedicarboxylate and its thiolated derivatives have been employed to assemble two dimolybdenum complex units and develop three Mo2 dimers, [Mo2(DAniF)3]2(μ-9,10-O2CC14H8CO2), [Mo2(DAniF)3]2(μ-9,10-OSCC14H8COS), and [Mo2(DAniF)3]2(μ-9,10-S2CC14H8CS2) (DAniF = N, N'-di( p-anisyl)formamidinate), for the study of conformation dependence of the electronic coupling between the two Mo2 centers. These compounds feature a large deviation of the central anthracene ring from the plane defined by the Mo-Mo bond vectors, with the torsion angles (ϕ = 50-76°) increasing as the chelating atoms of the bridging ligand vary from O to S. Consequently, the corresponding mixed-valence complexes do not exhibit characteristic intervalence charge transfer absorptions in the near-IR spectra, in contrast to the phenylene and naphthalene analogues, from which these systems are assigned to the Class I in Robin-Day's scheme. Together with the phenylene and naphthalene series, the nine total mixed-valence complexes in three series complete a transition from the electronically uncoupled Class I to the strongly coupled Class II-III borderline via moderately coupled Class II and permit a systematic mapping of the bridge conformation effects on electronic coupling. Density functional theory calculations show that the HOMO-LUMO energy gap, corresponding to the metal (δ) to ligand (π*) transition energy, and the magnitude of HOMO-HOMO-1 splitting in energy are linearly related to cos2 ϕ. Therefore, our experimental and theoretical results concur to indicate that the coupling strength decreases in the order of the bridging units: phenylene > naphthalene > anthracene, which verifies the through-bond superexchange mechanism for electronic coupling and electron transfer.
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Affiliation(s)
- Huo Wen Chen
- Department of Chemistry , Jinan University , 601 Huang-Pu Avenue West , Guangzhou 510632 , China
| | - Suman Mallick
- Department of Chemistry , Jinan University , 601 Huang-Pu Avenue West , Guangzhou 510632 , China
| | - Shan Feng Zou
- Department of Chemistry , Jinan University , 601 Huang-Pu Avenue West , Guangzhou 510632 , China
| | - Miao Meng
- Department of Chemistry , Jinan University , 601 Huang-Pu Avenue West , Guangzhou 510632 , China
| | - Chun Y Liu
- Department of Chemistry , Jinan University , 601 Huang-Pu Avenue West , Guangzhou 510632 , China
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Kundu M, He TF, Lu Y, Wang L, Zhong D. Short-Range Electron Transfer in Reduced Flavodoxin: Ultrafast Nonequilibrium Dynamics Coupled with Protein Fluctuations. J Phys Chem Lett 2018; 9:2782-2790. [PMID: 29722985 PMCID: PMC7304529 DOI: 10.1021/acs.jpclett.8b00882] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Short-range electron transfer (ET) in proteins is an ultrafast process on the similar time scales as local protein-solvent fluctuation, and thus the two dynamics are coupled. Here we use semiquinone flavodoxin and systematically characterized the photoinduced redox cycle with 11 mutations of different aromatic electron donors (tryptophan and tyrosine) and local residues to change redox properties. We observed the forward and backward ET dynamics in a few picoseconds, strongly following a stretched behavior resulting from a coupling between local environment relaxations and these ET processes. We further observed the hot vibrational-state formation through charge recombination and the subsequent cooling dynamics also in a few picoseconds. Combined with the ET studies in oxidized flavodoxin, these results coherently reveal the evolution of the ET dynamics from single to stretched exponential behaviors and thus elucidate critical time scales for the coupling. The observed hot vibration-state formation is robust and should be considered in all photoinduced back ET processes in flavoproteins.
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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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Trigger loop dynamics can explain stimulation of intrinsic termination by bacterial RNA polymerase without terminator hairpin contact. Proc Natl Acad Sci U S A 2017; 114:E9233-E9242. [PMID: 29078293 DOI: 10.1073/pnas.1706247114] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In bacteria, intrinsic termination signals cause disassembly of the highly stable elongating transcription complex (EC) over windows of two to three nucleotides after kilobases of RNA synthesis. Intrinsic termination is caused by the formation of a nascent RNA hairpin adjacent to a weak RNA-DNA hybrid within RNA polymerase (RNAP). Although the contributions of RNA and DNA sequences to termination are largely understood, the roles of conformational changes in RNAP are less well described. The polymorphous trigger loop (TL), which folds into the trigger helices to promote nucleotide addition, also is proposed to drive termination by folding into the trigger helices and contacting the terminator hairpin after invasion of the hairpin in the RNAP main cleft [Epshtein V, Cardinale CJ, Ruckenstein AE, Borukhov S, Nudler E (2007) Mol Cell 28:991-1001]. To investigate the contribution of the TL to intrinsic termination, we developed a kinetic assay that distinguishes effects of TL alterations on the rate at which ECs terminate from effects of the TL on the nucleotide addition rate that indirectly affect termination efficiency by altering the time window in which termination can occur. We confirmed that the TL stimulates termination rate, but found that stabilizing either the folded or unfolded TL conformation decreased termination rate. We propose that conformational fluctuations of the TL (TL dynamics), not TL-hairpin contact, aid termination by increasing EC conformational diversity and thus access to favorable termination pathways. We also report that the TL and the TL sequence insertion (SI3) increase overall termination efficiency by stimulating pausing, which increases the flux of ECs into the termination pathway.
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Inverted-region electron transfer as a mechanism for enhancing photosynthetic solar energy conversion efficiency. Proc Natl Acad Sci U S A 2017; 114:9267-9272. [PMID: 28814630 DOI: 10.1073/pnas.1704855114] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In all photosynthetic organisms, light energy is used to drive electrons from a donor chlorophyll species via a series of acceptors across a biological membrane. These light-induced electron-transfer processes display a remarkably high quantum efficiency, indicating a near-complete inhibition of unproductive charge recombination reactions. It has been suggested that unproductive charge recombination could be inhibited if the reaction occurs in the so-called inverted region. However, inverted-region electron transfer has never been demonstrated in any native photosynthetic system. Here we demonstrate that the unproductive charge recombination in native photosystem I photosynthetic reaction centers does occur in the inverted region, at both room and cryogenic temperatures. Computational modeling of light-induced electron-transfer processes in photosystem I demonstrate a marked decrease in photosynthetic quantum efficiency, from 98% to below 72%, if the unproductive charge recombination process does not occur in the inverted region. Inverted-region electron transfer is therefore demonstrated to be an important mechanism contributing to efficient solar energy conversion in photosystem I. Inverted-region electron transfer does not appear to be an important mechanism in other photosystems; it is likely because of the highly reducing nature of photosystem I, and the energetic requirements placed on the pigments to operate in such a regime, that the inverted-region electron transfer mechanism becomes important.
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Zanetti-Polzi L, Aschi M, Amadei A, Daidone I. Alternative Electron-Transfer Channels Ensure Ultrafast Deactivation of Light-Induced Excited States in Riboflavin Binding Protein. J Phys Chem Lett 2017; 8:3321-3327. [PMID: 28665138 DOI: 10.1021/acs.jpclett.7b01575] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Flavoproteins, containing flavin chromophores, are enzymes capable of transferring electrons at very high speeds. The ultrafast photoinduced electron-transfer (ET) kinetics of riboflavin binding protein to the excited riboflavin was studied by femtosecond spectroscopy and found to occur within a few hundred femtoseconds [ Zhong and Zewail, Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 11867-11872 ]. This ultrafast kinetics was attributed to the presence of two aromatic rings that could transfer the electron to riboflavin: the side chains of tryptophan 156 and tyrosine 75. However, the underlying ET mechanism remained unclear. Here, using a hybrid quantum mechanical-molecular dynamics approach, we perform ET dynamics simulations taking into account the motion of the protein and the solvent upon ET. This approach reveals that ET occurs via a major reaction channel involving tyrosine 75 (83%) and a minor one involving tryptophan 156 (17%). We also show that the protein environment is designed to ensure the fast quenching of the riboflavin excited state.
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Affiliation(s)
- Laura Zanetti-Polzi
- Department of Physical and Chemical Sciences, University of L'Aquila , via Vetoio (Coppito 1), 67010 L'Aquila, Italy
| | - Massimiliano Aschi
- Department of Physical and Chemical Sciences, University of L'Aquila , via Vetoio (Coppito 1), 67010 L'Aquila, Italy
| | - Andrea Amadei
- Department of Chemical and Technological Sciences, University of Rome "Tor Vergata" , Via della Ricerca Scientifica, 00185 Rome, Italy
| | - Isabella Daidone
- Department of Physical and Chemical Sciences, University of L'Aquila , via Vetoio (Coppito 1), 67010 L'Aquila, Italy
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