1
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Kang BJ, Rohwer EJ, Rohrbach D, Zyaee E, Akbarimoosavi M, Ollmann Z, Sorohhov G, Borgoo A, Cascella M, Cannizzo A, Decurtins S, Stanley RJ, Liu SX, Feurer T. Time-resolved THz Stark spectroscopy of molecules in solution. Nat Commun 2024; 15:4212. [PMID: 38760343 PMCID: PMC11101612 DOI: 10.1038/s41467-024-48164-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 04/22/2024] [Indexed: 05/19/2024] Open
Abstract
For decades, it was considered all but impossible to perform Stark spectroscopy on molecules in a liquid solution, because their concomitant orientation to the applied electric field results in overwhelming background signals. A way out was to immobilize the solute molecules by freezing the solvent. While mitigating solute orientation, freezing removes the possibility to study molecules in liquid environments at ambient conditions. Here we demonstrate time-resolved THz Stark spectroscopy, utilizing intense single-cycle terahertz pulses as electric field source. At THz frequencies, solute molecules have no time to orient their dipole moments. Hence, dynamic Stark spectroscopy on the time scales of molecular vibrations or rotations in both non-polar and polar solvents at arbitrary temperatures is now possible. We verify THz Stark spectroscopy for two judiciously selected molecular systems and compare the results to conventional Stark spectroscopy and first principle calculations.
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Affiliation(s)
- Bong Joo Kang
- Institute of Applied Physics, University of Bern, Bern, Switzerland
- Division of Advanced Materials, Korea Research Institute of Chemical Technology (KRICT), Daejeon, Republic of Korea
| | - Egmont J Rohwer
- Institute of Applied Physics, University of Bern, Bern, Switzerland
| | - David Rohrbach
- Institute of Applied Physics, University of Bern, Bern, Switzerland
| | - Elnaz Zyaee
- Institute of Applied Physics, University of Bern, Bern, Switzerland
| | | | - Zoltan Ollmann
- Institute of Applied Physics, University of Bern, Bern, Switzerland
| | - Gleb Sorohhov
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Alex Borgoo
- Department of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, Oslo, Norway
| | - Michele Cascella
- Department of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, Oslo, Norway
| | - Andrea Cannizzo
- Institute of Applied Physics, University of Bern, Bern, Switzerland
| | - Silvio Decurtins
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Robert J Stanley
- Department of Chemistry, Temple University, Philadelphia, PA, USA
| | - Shi-Xia Liu
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Thomas Feurer
- Institute of Applied Physics, University of Bern, Bern, Switzerland.
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2
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Van Galen CJ, Pauszek RF, Koder RL, Stanley RJ. Flavin Charge Redistribution upon Optical Excitation Is Independent of Solvent Polarity. J Phys Chem B 2023; 127:661-672. [PMID: 36649202 DOI: 10.1021/acs.jpcb.2c07266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Flavin absorption spectra encode molecular details of the flavin's local environment through coupling of local electric fields with the chromophore's charge redistribution upon optical excitation. Translating experimentally measured field-tuned transition energies to local electric field magnitudes and directions across a wide range of field magnitudes requires that the charge redistribution be independent of the local field. We have measured the charge redistribution upon optical excitation of the derivatized flavin TPARF in the non-hydrogen-bonding, nonpolar solvent toluene, with and without a tridentate hydrogen-bonding ligand, DBAP, using electronic Stark spectroscopy. These measurements were interpreted using TD-DFT finite field and difference density calculations. In comparing our present results to previous Stark spectroscopic analyses of flavin in more polar solvents, we conclude that flavin charge redistribution upon optical excitation is independent of solvent polarity, indicating that dependence of flavin transition energies on local field magnitude is linear with local field magnitude.
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Affiliation(s)
- Cornelius J Van Galen
- Department of Chemistry, Temple University, 1901 N. 13th St., 250B Beury Hall, Philadelphia, Pennsylvania19122, United States
| | - Raymond F Pauszek
- Department of Chemistry, Temple University, 1901 N. 13th St., 250B Beury Hall, Philadelphia, Pennsylvania19122, United States
| | - Ronald L Koder
- Department of Physics, The City College of New York, 1.308 CDI Bldg., 85 St. Nicholas Terrace, New York, New York10031, United States
| | - Robert J Stanley
- Department of Chemistry, Temple University, 1901 N. 13th St., 250B Beury Hall, Philadelphia, Pennsylvania19122, United States
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3
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Hontani Y, Mehlhorn J, Domratcheva T, Beck S, Kloz M, Hegemann P, Mathes T, Kennis JTM. Spectroscopic and Computational Observation of Glutamine Tautomerization in the Blue Light Sensing Using Flavin Domain Photoreaction. J Am Chem Soc 2023; 145:1040-1052. [PMID: 36607126 PMCID: PMC9853863 DOI: 10.1021/jacs.2c10621] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Blue light sensing using flavin (BLUF) domains constitute a family of flavin-binding photoreceptors of bacteria and eukaryotic algae. BLUF photoactivation proceeds via a light-driven hydrogen-bond switch among flavin adenine dinucleotide (FAD) and glutamine and tyrosine side chains, whereby FAD undergoes electron and proton transfer with tyrosine and is subsequently re-oxidized by a hydrogen back-shuttle in picoseconds, constituting an important model system to understand proton-coupled electron transfer in biology. The specific structure of the hydrogen-bond patterns and the prevalence of glutamine tautomeric states in dark-adapted (DA) and light-activated (LA) states have remained controversial. Here, we present a combined femtosecond stimulated Raman spectroscopy (FSRS), computational chemistry, and site-selective isotope labeling Fourier-transform infrared spectroscopy (FTIR) study of the Slr1694 BLUF domain. FSRS showed distinct vibrational bands from the FADS1 singlet excited state. We observed small but significant shifts in the excited-state vibrational frequency patterns of the DA and LA states, indicating that these frequencies constitute a sensitive probe for the hydrogen-bond arrangement around FAD. Excited-state model calculations utilizing four different realizations of hydrogen bond patterns and glutamine tautomeric states were consistent with a BLUF reaction model that involved glutamine tautomerization to imidic acid, accompanied by a rotation of its side chain. A combined FTIR and double-isotope labeling study, with 13C labeling of FAD and 15N labeling of glutamine, identified the glutamine imidic acid C═N stretch vibration in the LA state and the Gln C═O in the DA state. Hence, our study provides support for glutamine tautomerization and side-chain rotation in the BLUF photoreaction.
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Affiliation(s)
- Yusaku Hontani
- Department
of Physics and Astronomy, Vrije Universiteit
Amsterdam, 1081 HV Amsterdam, De Boelelaan, The Netherlands
| | - Jennifer Mehlhorn
- Institut
für Biologie, Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstrasse 42, D-10115 Berlin, Germany
| | - Tatiana Domratcheva
- Department
of Biomolecular Mechanisms, Max Planck Institute
for Medical Research, 69120 Heidelberg, Germany,Department
of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Sebastian Beck
- Department
of Chemistry, Humboldt-Universität
zu Berlin, Brook-Taylor-Str.
2, 12489 Berlin, Germany
| | - Miroslav Kloz
- Department
of Physics and Astronomy, Vrije Universiteit
Amsterdam, 1081 HV Amsterdam, De Boelelaan, The Netherlands,Institute
of Physics, ELI-Beamlines, Na Slovance 2, 182
21 Praha 8, Czech Republic
| | - Peter Hegemann
- Institut
für Biologie, Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstrasse 42, D-10115 Berlin, Germany
| | - Tilo Mathes
- Department
of Physics and Astronomy, Vrije Universiteit
Amsterdam, 1081 HV Amsterdam, De Boelelaan, The Netherlands,Institut
für Biologie, Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstrasse 42, D-10115 Berlin, Germany
| | - John T. M. Kennis
- Department
of Physics and Astronomy, Vrije Universiteit
Amsterdam, 1081 HV Amsterdam, De Boelelaan, The Netherlands,
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4
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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: 5] [Impact Index Per Article: 2.5] [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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5
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Understanding flavin electronic structure and spectra. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1541] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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6
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Kar RK, Chasen S, Mroginski MA, Miller AF. Tuning the Quantum Chemical Properties of Flavins via Modification at C8. J Phys Chem B 2021; 125:12654-12669. [PMID: 34784473 DOI: 10.1021/acs.jpcb.1c07306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Flavins are central to countless enzymes but display different reactivities depending on their environments. This is understood to reflect modulation of the flavin electronic structure. To understand changes in orbital natures, energies, and correlation over the ring system, we begin by comparing seven flavin variants differing at C8, exploiting their different electronic spectra to validate quantum chemical calculations. Ground state calculations replicate a Hammett trend and reveal the significance of the flavin π-system. Comparison of higher-level theories establishes CC2 and ACD(2) as methods of choice for characterization of electronic transitions. Charge transfer character and electron correlation prove responsive to the identity of the substituent at C8. Indeed, bond length alternation analysis demonstrates extensive conjugation and delocalization from the C8 position throughout the ring system. Moreover, we succeed in replicating a particularly challenging UV/Vis spectrum by implementing hybrid QM/MM in explicit solvents. Our calculations reveal that the presence of nonbonding lone pairs correlates with the change in the UV/Vis spectrum observed when the 8-methyl is replaced by NH2, OH, or SH. Thus, our computations offer routes to understanding the spectra of flavins with different modifications. This is a first step toward understanding how the same is accomplished by different binding environments.
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Affiliation(s)
- Rajiv K Kar
- Faculty II-Mathematics and Natural Sciences, Technische Universität Berlin, Sekr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - Sam Chasen
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Maria-Andrea Mroginski
- Faculty II-Mathematics and Natural Sciences, Technische Universität Berlin, Sekr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - Anne-Frances Miller
- Faculty II-Mathematics and Natural Sciences, Technische Universität Berlin, Sekr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany.,Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
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7
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Dratch BD, Orozco-Gonzalez Y, Gadda G, Gozem S. Ionic Atmosphere Effect on the Absorption Spectrum of a Flavoprotein: A Reminder to Consider Solution Ions. J Phys Chem Lett 2021; 12:8384-8396. [PMID: 34435784 DOI: 10.1021/acs.jpclett.1c02173] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
This study utilizes the FMN-dependent NADH:quinone oxidoreductase from Pseudomonas aeruginosa PAO1 to investigate the effect of introducing an active site negative charge on the flavin absorption spectrum both in the absence and presence of a long-range electrostatic potential coming from solution ions. There were no observed changes in the flavin UV-visible spectrum when an active site tyrosine (Y277) becomes deprotonated in vitro. These results could only be reproduced computationally using average solvent electrostatic configuration (ASEC) QM/MM simulations that include both positive and negative solution ions. The same calculations performed with minimal ions to neutralize the total protein charge predicted that deprotonating Y277 would significantly alter the flavin absorption spectrum. Analyzing the distribution of solution ions indicated that the ions reorganize around the protein surface upon Y277 deprotonation to cancel the effect of the tyrosinate on the flavin absorption spectrum. Additional biochemical experiments were performed to test this hypothesis.
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Affiliation(s)
- Benjamin D Dratch
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | | | - Giovanni Gadda
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
- Department of Biology, Georgia State University, Atlanta, Georgia 30302, United States
- Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302, United States
| | - Samer Gozem
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
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8
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Varner TA, Mohamed-Raseek N, Miller AF. Assignments of 19F NMR resonances and exploration of dynamics in a long-chain flavodoxin. Arch Biochem Biophys 2021; 703:108839. [PMID: 33727041 DOI: 10.1016/j.abb.2021.108839] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 03/04/2021] [Accepted: 03/09/2021] [Indexed: 12/23/2022]
Abstract
Flavodoxin is a small protein that employs a non-covalently bound flavin to mediate single-electron transfer at low potentials. The long-chain flavodoxins possess a long surface loop that is proposed to interact with partner proteins. We have incorporated 19F-labeled tyrosine in long-chain flavodoxin from Rhodopseudomonas palustris to gain a probe of possible loop dynamics, exploiting the presence of a Tyr in the long loop in addition to Tyr residues near the flavin. We report 19F resonance assignments for all four Tyrs, and demonstration of a pair of resonances in slow exchange, both corresponding to a Tyr adjacent to the flavin. We also provide evidence for dynamics affecting the Tyr in the long loop. Thus, we show that 19F NMR of 19F-Tyr labeled flavodoxin holds promise for monitoring possible changes in conformation upon binding to partner proteins.
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Affiliation(s)
- Taylor A Varner
- Department of Chemistry, University of Kentucky, Lexington, KY, 40506, USA
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9
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Rohwer EJ, Geng Y, Akbarimoosavi M, Daku LML, Aleveque O, Levillain E, Hauser J, Cannizzo A, Häner R, Decurtins S, Stanley RJ, Feurer T, Liu SX. Optically Controlled Electron Transfer in a Re I Complex. Chemistry 2021; 27:5399-5403. [PMID: 33524171 DOI: 10.1002/chem.202005125] [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: 11/26/2020] [Indexed: 11/09/2022]
Abstract
Ultrafast optical control of intramolecular charge flow was demonstrated, which paves the way for photocurrent modulation and switching with a highly wavelength-selective ON/OFF ratio. The system that was explored is a fac-[Re(CO)3 (TTF-DPPZ)Cl] complex, where TTF-DPPZ=4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2',3'-c]phenazine. DFT calculations and AC-Stark spectroscopy confirmed the presence of two distinct optically active charge-transfer processes, namely a metal-to-ligand charge transfer (MLCT) and an intra-ligand charge transfer (ILCT). Ultrafast transient absorption measurements showed that the ILCT state decays in the ps regime. Upon excitation to the MLCT state, only a long-lived 3 MLCT state was observed after 80 ps. Remarkably, however, the bleaching of the ILCT absorption band remained as a result of the effective inhibition of the HOMO-LUMO transition.
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Affiliation(s)
- Egmont J Rohwer
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - Yan Geng
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland.,Present address: College of Chemistry, Chemical Engineering and Material Science, Shandong Normal University, Jinan, 250014, P. R. China
| | - Maryam Akbarimoosavi
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - Latévi M Lawson Daku
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest Ansermet, 1211, Geneva, Switzerland
| | | | - Eric Levillain
- CNRS, MOLTECH-ANJOU, UNIV Angers, Angers, F-49000, France
| | - Jürg Hauser
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Andrea Cannizzo
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - Robert Häner
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Silvio Decurtins
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Robert J Stanley
- Department of Chemistry, Temple University, Pennsylvania, Philadelphia, Pennsylvania, 19122, USA
| | - Thomas Feurer
- Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - Shi-Xia Liu
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
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10
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van Galen C, Barnard DT, Stanley RJ. Stark Spectroscopy of Lumichrome: A Possible Candidate for Stand-Off Detection of Bacterial Quorum Sensing. J Phys Chem B 2020; 124:11835-11842. [PMID: 33325706 PMCID: PMC8714027 DOI: 10.1021/acs.jpcb.0c09498] [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: 01/20/2023]
Abstract
Lumichrome (7,8-dimethylalloxazine, LC) is a natural photodegradation product and catabolite of flavin coenzymes. Although not a coenzyme itself, LC is used for biosignaling in plants and single-celled organisms, including quorum sensing in the formation of biofilms. The noninvasive detection of in vivo lumichrome would be useful for monitoring this signaling event. For molecules that undergo significant charge redistribution upon light excitation (e.g., intramolecular charge transfer), there are optical detection methods (e.g., second-harmonic generation) that would be well suited to this task. Here, we have used Stark spectroscopy to measure the extent and direction of charge redistribution in photoexcited LC. Stark and low-temperature absorption spectra were obtained at 77 K on LC in ethanol glasses and analyzed using the Liptay analysis to obtain the difference dipole moments and polarizabilities. These data were complemented by a computational analysis of the excited states using density functional theory (DFT) at the TD-B3LYP/6-311+G(2d,p) level of theory.
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Affiliation(s)
- Cornelius van Galen
- Department of Chemistry, Temple University, 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - David T Barnard
- Department of Chemistry, Temple University, 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Robert J Stanley
- Department of Chemistry, Temple University, 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
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11
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Structural distortion and electron redistribution in dual-emitting gold nanoclusters. Nat Commun 2020; 11:2897. [PMID: 32518297 PMCID: PMC7283347 DOI: 10.1038/s41467-020-16686-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 05/19/2020] [Indexed: 01/09/2023] Open
Abstract
Deciphering the complicated excited-state process is critical for the development of luminescent materials with controllable emissions in different applications. Here we report the emergence of a photo-induced structural distortion accompanied by an electron redistribution in a series of gold nanoclusters. Such unexpected slow process of excited-state transformation results in near-infrared dual emission with extended photoluminescent lifetime. We demonstrate that this dual emission exhibits highly sensitive and ratiometric response to solvent polarity, viscosity, temperature and pressure. Thus, a versatile luminescent nano-sensor for multiple environmental parameters is developed based on this strategy. Furthermore, we fully unravel the atomic-scale structural origin of this unexpected excited-state transformation, and demonstrate control over the transition dynamics by tailoring the bi-tetrahedral core structures of gold nanoclusters. Overall, this work provides a substantial advance in the excited-state physical chemistry of luminescent nanoclusters and a general strategy for the rational design of next-generation nano-probes, sensors and switches.
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12
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Liu T, Foo Y, Zapien JA, Li M, Tsang SW. A generalized Stark effect electromodulation model for extracting excitonic properties in organic semiconductors. Nat Commun 2019; 10:5089. [PMID: 31704917 PMCID: PMC6841700 DOI: 10.1038/s41467-019-13081-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 10/15/2019] [Indexed: 11/30/2022] Open
Abstract
Electromodulation (EM) spectroscopy, a powerful technique to monitor the changes in polarizability p and dipole moment u of materials upon photo-excitation, can bring direct insight into the excitonic properties of materials. However, extracting Δp and Δu from the electromodulation spectrum relies on fitting with optical absorption of the materials where optical effect in different device geometries might introduce large variation in the extracted values. Here, we demonstrate a systematic electromodulation study with various fitting approaches in both commonly adopted reflection and transmission device architectures. Strikingly, we have found that the previously ascribed continuum state threshold from the deviation between the measured and fitting results is questionable. Such deviation is found to be caused by the overlooked optical interference and electrorefraction effect. A generalized electromodulation model is proposed to incorporate the two effects, and the extracted Δp and Δu have excellent consistency in both reflection and transmission modes in all organic film thicknesses. The development of a generalized electromodulation (EM) spectroscopy model that accurately extracts material parameters for organic electronics remains a challenge. Here, the authors report an EM model that enhances parameter extraction accuracy by accounting for optical interference effects.
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Affiliation(s)
- Taili Liu
- Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China.,Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China.,City University of Hong Kong Shenzhen Research Institute, 8 Yuexing No.1 Ave, Nanshan District, Shenzhen, Guangdong, P. R. China
| | - Yishu Foo
- Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China.,Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China
| | - Juan Antonio Zapien
- Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China.,Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China
| | - Menglin Li
- Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China.,Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China.,City University of Hong Kong Shenzhen Research Institute, 8 Yuexing No.1 Ave, Nanshan District, Shenzhen, Guangdong, P. R. China
| | - Sai-Wing Tsang
- Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China. .,Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Ave, Kowloon Tong, Hong Kong SAR, P. R. China. .,City University of Hong Kong Shenzhen Research Institute, 8 Yuexing No.1 Ave, Nanshan District, Shenzhen, Guangdong, P. R. China.
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13
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Davydov RM, Jennings G, Hoffman BM, Podust LM. Short-lived neutral FMN and FAD semiquinones are transient intermediates in cryo-reduced yeast NADPH-cytochrome P450 reductase. Arch Biochem Biophys 2019; 673:108080. [PMID: 31445894 DOI: 10.1016/j.abb.2019.108080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 08/14/2019] [Accepted: 08/20/2019] [Indexed: 11/28/2022]
Abstract
The electron configuration of flavin cofactors, FMN and FAD, is a critical factor governing the reactivity of NADPH-cytochrome P450 reductase (CPR). The current view of electron transfer by the mammalian CPR, based on equilibrium redox potentials of the flavin cofactors, is that the two electron-reduced FMN hydroquinone (FMNH2), rather than one electron-reduced FMN semiquinone, serves as electron donor to the terminal protein acceptors. However, kinetic and thermodynamic studies on the CPR species originated from different organisms have shown that redox potentials measured at distinct electron transfer steps differ from redox potentials determined by equilibrium titration. Collectively, previous observations suggest that the short-lived transient semiquinone species may carry electrons in diflavin reductases. In this work, we have investigated spectroscopic properties of the CPR-bound FAD and FMN reduced at 77 K by radiolytically-generated thermalized electrons. Using UV-vis spectroscopy, we demonstrated that upon cryo-reduction of oxidized yeast CPR (yCPR) containing an equimolar ratio of both FAD and FMN, or FAD alone, neutral semiquinones were trapped at 77 K. During annealing at the elevated temperatures, unstable short-lived neutral semiquinones relaxed to spectroscopically distinct air-stable neutral semiquinones. This transition was independent of pH within the 6.0-10.7 range. Our data on yeast CPR are in line with the previous observations of others that the flavin short-lived transient semiquinone intermediates may have a role in the electron transfer by CPR at physiological conditions.
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Affiliation(s)
- Roman M Davydov
- The Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Gareth Jennings
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Brian M Hoffman
- The Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Larissa M Podust
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.
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14
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Stanley RJ, van Galen CJ. Measuring electronic structure properties of flavins and flavoproteins by electronic Stark spectroscopy. Methods Enzymol 2019; 620:215-250. [PMID: 31072488 PMCID: PMC7301760 DOI: 10.1016/bs.mie.2019.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The optical spectrum of a flavoprotein is one of its signature properties. No two flavoprotein absorption spectra are exactly alike as each encodes the details of the interaction of the flavin cofactor electronic structure with the specific protein binding pocket. Electronic Stark spectroscopy has the potential to elucidate these interactions with high sensitivity, at low cost, and requiring minimal technical sophistication. In this chapter we will outline the theoretical basis for Stark spectroscopy and describe the construction of the Stark spectrometer. Step-by-step instructions are given for acquiring and interpreting Stark spectra to retrieve difference moments of the flavin ground versus excited state charge distributions.
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Affiliation(s)
- Robert J Stanley
- Department of Chemistry, Temple University, Philadelphia, PA, United States.
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15
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Ye S, Tan J, Tian K, Li C, Zhang J, Luo Y. Directly monitoring the active sites of charge transfer in heterocycles in situ and in real time. Chem Commun (Camb) 2019; 55:541-544. [PMID: 30556076 DOI: 10.1039/c8cc08452a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Coherent degenerate infrared-infrared-visible sum frequency generation vibrational spectroscopy provides a powerful label-free sensitive probe for charge transfer active sites in heterocyclic molecules in situ and in real time.
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Affiliation(s)
- Shuji Ye
- Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center for Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
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16
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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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17
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Characterization of a cold-adapted DNA photolyase from C. psychrerythraea 34H. Extremophiles 2017; 21:919-932. [PMID: 28726126 DOI: 10.1007/s00792-017-0953-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 07/09/2017] [Indexed: 10/19/2022]
Abstract
The phrB gene encoding a putative cold-adapted DNA photolyase was cloned from the bacterial genomic DNA of Colwellia psychrerythraea 34H, a psychrophilic bacterium. Recombinant DNA photolyase, rCpPL, was overexpressed and purified from three different vectors. rCpPL binds its DNA substrate by flipping a cyclobutane pyrimidine dimer (CPD) into its active site and repairs CPD-containing DNA in vitro. rCpPL contains one catalytic flavin adenine dinucleotide (FAD) cofactor, but displays promiscuity in cofactor binding, in which either a flavin mononucleotide (FMN) or a methenyltetrahydrofolate (MTHF) molecule is bound as an antenna molecule and found in sub-stoichiometric amounts. The UV/Vis spectrum of oxidized rCpPL shows that the FADOX absorption maximum is the most red-shifted reported for a PL, suggesting a unique cavity electrostatic environment. Modest FAD vibronic structure suggests that the binding pocket is more flexible than warmer PLs, corroborating the hypothesis that psychrophilic proteins must be highly flexible to function at low temperatures. Fluorescence excitation data show that the freshly purified flavin cofactor is in its fully reduced state (FADH¯). A homology analysis of PL protein structures spanning 70 °C in growth temperature supports the data that the structure of CpPL is quite different from its warmer cousins.
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18
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Gil AA, Laptenok SP, French JB, Iuliano JN, Lukacs A, Hall CR, Sazanovich IV, Greetham GM, Bacher A, Illarionov B, Fischer M, Tonge PJ, Meech SR. Femtosecond to Millisecond Dynamics of Light Induced Allostery in the Avena sativa LOV Domain. J Phys Chem B 2017; 121:1010-1019. [PMID: 28068090 DOI: 10.1021/acs.jpcb.7b00088] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rational engineering of photosensor proteins underpins the field of optogenetics, in which light is used for spatiotemporal control of cell signaling. Optogenetic elements function by converting electronic excitation of an embedded chromophore into structural changes on the microseconds to seconds time scale, which then modulate the activity of output domains responsible for biological signaling. Using time-resolved vibrational spectroscopy coupled with isotope labeling, we have mapped the structural evolution of the LOV2 domain of the flavin binding phototropin Avena sativa (AsLOV2) over 10 decades of time, reporting structural dynamics between 100 fs and 1 ms after optical excitation. The transient vibrational spectra contain contributions from both the flavin chromophore and the surrounding protein matrix. These contributions are resolved and assigned through the study of four different isotopically labeled samples. High signal-to-noise data permit the detailed analysis of kinetics associated with the light activated structural evolution. A pathway for the photocycle consistent with the data is proposed. The earliest events occur in the flavin binding pocket, where a subpicosecond perturbation of the protein matrix occurs. In this perturbed environment, the previously characterized reaction between triplet state isoalloxazine and an adjacent cysteine leads to formation of the adduct state; this step is shown to exhibit dispersive kinetics. This reaction promotes coupling of the optical excitation to successive time-dependent structural changes, initially in the β-sheet and then α-helix regions of the AsLOV2 domain, which ultimately gives rise to Jα-helix unfolding, yielding the signaling state. This model is tested through point mutagenesis, elucidating in particular the key mediating role played by Q513.
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Affiliation(s)
- Agnieszka A Gil
- Department of Chemistry, Stony Brook University , New York 11794-3400, United States
| | - Sergey P Laptenok
- School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, U.K
| | - Jarrod B French
- Department of Chemistry, Stony Brook University , New York 11794-3400, United States
| | - James N Iuliano
- Department of Chemistry, Stony Brook University , New York 11794-3400, United States
| | - Andras Lukacs
- School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, U.K.,Department of Biophysics, Medical School, University of Pecs , Szigeti ut 12, 7624 Pecs, Hungary
| | | | - Igor V Sazanovich
- Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory , Didcot, Oxon OX11 0QX, U.K
| | - Gregory M Greetham
- Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory , Didcot, Oxon OX11 0QX, U.K
| | - Adelbert Bacher
- Department Chemie, Technische Universität München , D-85747 Garching, Germany
| | - Boris Illarionov
- Institut für Biochemie und Lebensmittelchemie, Universität Hamburg , Grindelallee 117, D-20146 Hamburg, Germany
| | - Markus Fischer
- Institut für Biochemie und Lebensmittelchemie, Universität Hamburg , Grindelallee 117, D-20146 Hamburg, Germany
| | - Peter J Tonge
- Department of Chemistry, Stony Brook University , New York 11794-3400, United States
| | - Stephen R Meech
- School of Chemistry, University of East Anglia , Norwich, NR4 7TJ, U.K
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19
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Pauszek RF, Kodali G, Siddiqui MSU, Stanley RJ. Overlapping Electronic States with Nearly Parallel Transition Dipole Moments in Reduced Anionic Flavin Can Distort Photobiological Dynamics. J Am Chem Soc 2016; 138:14880-14889. [PMID: 27686753 DOI: 10.1021/jacs.6b06449] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chromophoric biomolecules are exploited as reporters of a diverse set of phenomena, acting as internal distance monitors, environment and redox sensors, and endogenous imaging probes. The extent to which they can be exploited is dependent on an accurate knowledge of their fundamental electronic properties. Arguably of greatest importance is a precise knowledge of the direction(s) of the absorption transition dipole moment(s) (TDMs) in the molecular frame of reference. Such is the case for flavins, fluorescent redox cofactors utilized for ground- and excited-state redox and photochemical processes. The directions of the TDMs in oxidized and semiquinone flavins were characterized decades ago, and the details of charge redistribution in these forms have also been studied by Stark spectroscopy. The electronic structure of the fully reduced hydroquinone anionic state, FlH-, however, has been the subject of unfounded assumptions and estimates about the number and direction of TDMs in FlH-, as well the electronic structure changes that occur upon light absorption. Here we have used Stark spectroscopy to measure the magnitude and direction of charge redistribution in FlH- upon optical excitation. These data were analyzed using TD-DFT calculations. The results show unequivocally that not one but two nearly orientation-degenerate electronic transitions are required to explain the 340-500 nm absorption spectral range, demolishing the commonly held assumption of a single transition. The difference dipole moments for these states show that electron density shifts toward the xylene ring for both transitions. These measurements force a reappraisal of previous studies that have used erroneous assumptions and unsubstantiated estimates of these quantities. The results put future optical studies of reduced flavins/flavoproteins on a firm photophysical footing.
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Affiliation(s)
- Raymond F Pauszek
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Goutham Kodali
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - M Salim U Siddiqui
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Robert J Stanley
- Department of Chemistry, Temple University , 250B Beury Hall, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
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20
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Electron flow through biological molecules: does hole hopping protect proteins from oxidative damage? Q Rev Biophys 2016; 48:411-20. [PMID: 26537399 DOI: 10.1017/s0033583515000062] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Biological electron transfers often occur between metal-containing cofactors that are separated by very large molecular distances. Employing photosensitizer-modified iron and copper proteins, we have shown that single-step electron tunneling can occur on nanosecond to microsecond timescales at distances between 15 and 20 Å. We also have shown that charge transport can occur over even longer distances by hole hopping (multistep tunneling) through intervening tyrosines and tryptophans. In this perspective, we advance the hypothesis that such hole hopping through Tyr/Trp chains could protect oxygenase, dioxygenase, and peroxidase enzymes from oxidative damage. In support of this view, by examining the structures of P450 (CYP102A) and 2OG-Fe (TauD) enzymes, we have identified candidate Tyr/Trp chains that could transfer holes from uncoupled high-potential intermediates to reductants in contact with protein surface sites.
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21
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Lee W, Kodali G, Stanley RJ, Matsika S. Coexistence of Different Electron-Transfer Mechanisms in the DNA Repair Process by Photolyase. Chemistry 2016; 22:11371-81. [PMID: 27362906 DOI: 10.1002/chem.201600656] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 05/18/2016] [Indexed: 11/07/2022]
Abstract
DNA photolyase has been the topic of extensive studies due to its important role of repairing photodamaged DNA, and its unique feature of using light as an energy source. A crucial step in the repair by DNA photolyase is the forward electron transfer from its cofactor (FADH(-) ) to the damaged DNA, and the detailed mechanism of this process has been controversial. In the present study, we examine the forward electron transfer in DNA photolyase by carrying out high-level ab initio calculations in combination with a quantum mechanical/molecular mechanical (QM/MM) approach, and by measuring fluorescence emission spectra at low temperature. On the basis of these computational and experimental results, we demonstrate that multiple decay pathways exist in DNA photolyase depending on the wavelength at excitation and the subsequent transition. This implies that the forward electron transfer in DNA photolyase occurs not only by superexchange mechanism but also by sequential electron transfer.
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Affiliation(s)
- Wook Lee
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania, 19122, USA.
| | - Goutham Kodali
- Teva Pharmaceuticals USA, Inc, 145 Brandywine Pkwy, West Chester, Pennsylvania, 19380, USA
| | - Robert J Stanley
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania, 19122, USA
| | - Spiridoula Matsika
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania, 19122, USA
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22
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Abstract
Photolyases, a class of flavoproteins, use blue light to repair two types of ultraviolet-induced DNA damage, a cyclobutane pyrimidine dimer (CPD) and a pyrimidine-pyrimidone (6-4) photoproduct (6-4PP). In this perspective, we review the recent progress in the repair dynamics and mechanisms of both types of DNA restoration by photolyases. We first report the spectroscopic characterization of flavin in various redox states and the active-site solvation dynamics in photolyases. We then systematically summarize the detailed repair dynamics of damaged DNA by photolyases and a biomimetic system through resolving all elementary steps on ultrafast timescales, including multiple intermolecular electron- and proton-transfer reactions and bond-breaking and -making processes. We determined the unique electron tunneling pathways, identified the key functional residues and revealed the molecular origin of high repair efficiency, and thus elucidate the molecular mechanisms and repair photocycles at the most fundamental level. We finally conclude that the active sites of photolyases, unlike the aqueous solution for the biomimetic system, provide a unique electrostatic environment and local flexibility and thus a dedicated synergy for all elementary dynamics to maximize the repair efficiency. This repair photomachine is the first enzyme that the entire functional evolution is completely mapped out in real time.
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Affiliation(s)
- Zheyun Liu
- Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
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23
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Paulus B, Bajzath C, Melin F, Heidinger L, Kromm V, Herkersdorf C, Benz U, Mann L, Stehle P, Hellwig P, Weber S, Schleicher E. Spectroscopic characterization of radicals and radical pairs in fruit fly cryptochrome - protonated and nonprotonated flavin radical-states. FEBS J 2015; 282:3175-89. [PMID: 25879256 DOI: 10.1111/febs.13299] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/21/2015] [Accepted: 04/14/2015] [Indexed: 01/05/2023]
Abstract
Drosophila melanogaster cryptochrome is one of the model proteins for animal blue-light photoreceptors. Using time-resolved and steady-state optical spectroscopy, we studied the mechanism of light-induced radical-pair formation and decay, and the photoreduction of the FAD cofactor. Exact kinetics on a microsecond to minutes timescale could be extracted for the wild-type protein using global analysis. The wild-type exhibits a fast photoreduction reaction from the oxidized FAD to the FAD(•-) state with a very positive midpoint potential of ~ +125 mV, although no further reduction could be observed. We could also demonstrate that the terminal tryptophan of the conserved triad, W342, is directly involved in electron transfer; however, photoreduction could not be completely inhibited in a W342F mutant. The investigation of another mutation close to the FAD cofactor, C416N, rather unexpectedly reveals accumulation of a protonated flavin radical on a timescale of several seconds. The obtained data are critically discussed with the ones obtained from another protein, Escherichia coli photolyase, and we conclude that the amino acid opposite N(5) of the isoalloxazine moiety of FAD is able to (de)stabilize the protonated FAD radical but not to significantly modulate the kinetics of any light-inducted reactions.
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Affiliation(s)
- Bernd Paulus
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Csaba Bajzath
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Frédéric Melin
- Laboratoire de Bioélectrochimie et Spectroscopie Université de Strasbourg, France
| | - Lorenz Heidinger
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Viktoria Kromm
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | | | - Ulrike Benz
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Lisa Mann
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Patricia Stehle
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Petra Hellwig
- Laboratoire de Bioélectrochimie et Spectroscopie Université de Strasbourg, France
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Erik Schleicher
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
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24
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Winkler JR, Gray HB. Could tyrosine and tryptophan serve multiple roles in biological redox processes? PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:rsta.2014.0178. [PMID: 25666062 PMCID: PMC4342971 DOI: 10.1098/rsta.2014.0178] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Single-step electron tunnelling reactions can transport charges over distances of 15-20 Åin proteins. Longer-range transfer requires multi-step tunnelling processes along redox chains, often referred to as hopping. Long-range hopping via oxidized radicals of tryptophan and tyrosine, which has been identified in several natural enzymes, has been demonstrated in artificial constructs of the blue copper protein azurin. Tryptophan and tyrosine serve as hopping way stations in high-potential charge transport processes. It may be no coincidence that these two residues occur with greater-than-average frequency in O(2)- and H(2)O(2)-reactive enzymes. We suggest that appropriately placed tyrosine and/or tryptophan residues prevent damage from high-potential reactive intermediates by reduction followed by transfer of the oxidizing equivalent to less harmful sites or out of the protein altogether.
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Affiliation(s)
- Jay R Winkler
- Beckman Institute, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA
| | - Harry B Gray
- Beckman Institute, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA
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25
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Miller AF. Solid-state NMR of flavins and flavoproteins. Methods Mol Biol 2014; 1146:307-40. [PMID: 24764096 DOI: 10.1007/978-1-4939-0452-5_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Why apply solid-state NMR (SSNMR) to flavins and flavoproteins? NMR provides information on an atom-specific basis about chemical functionality, structure, proximity to other groups, and dynamics of the system. Thus, it has become indispensable to the study of chemicals, materials, catalysts, and biomolecules. It is no surprise then that NMR has a great deal to offer in the study of flavins and flavoenzymes. In general, their catalytic or electron-transfer activity resides essentially in the flavin, a molecule eminently accessible by NMR. However, the specific reactivity displayed depends on a host of subtle interactions whereby the protein biases and reshapes the flavin's propensities to activate it for one reaction while suppressing other aspects of this cofactor's prodigious repertoire (Massey et al., J Biol Chem 244:3999-4006, 1969; Müller, Z Naturforsch 27B:1023-1026, 1972; Joosten and van Berkel, Curr Opin Struct Biol 11:195-202, 2007). Thus, we are fascinated to learn about how the flavin cofactor of one enzyme is, and is not, like the flavin cofactor of another. In what follows, we describe how the capabilities of SSNMR can help and are beginning to bear fruit in this exciting endeavor.
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Affiliation(s)
- Anne-Frances Miller
- Department of Chemistry, University of Kentucky, 505 Rose St, Lexington, KY, 40506-0055, USA,
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26
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Affiliation(s)
- Jay R. Winkler
- Beckman Institute, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125
| | - Harry B. Gray
- Beckman Institute, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125
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27
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Abstract
Electrons have so little mass that in less than a second they can tunnel through potential energy barriers that are several electron-volts high and several nanometers wide. Electron tunneling is a critical functional element in a broad spectrum of applications, ranging from semiconductor diodes to the photosynthetic and respiratory charge transport chains. Prior to the 1970s, chemists generally believed that reactants had to collide in order to effect a transformation. Experimental demonstrations that electrons can transfer between reactants separated by several nanometers led to a revision of the chemical reaction paradigm. Experimental investigations of electron exchange between redox partners separated by molecular bridges have elucidated many fundamental properties of these reactions, particularly the variation of rate constants with distance. Theoretical work has provided critical insights into the superexchange mechanism of electronic coupling between distant redox centers. Kinetics measurements have shown that electrons can tunnel about 2.5 nm through proteins on biologically relevant time scales. Longer-distance biological charge flow requires multiple electron tunneling steps through chains of redox cofactors. The range of phenomena that depends on long-range electron tunneling continues to expand, providing new challenges for both theory and experiment.
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Affiliation(s)
- Jay R. Winkler
- Beckman Institute, California
Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Harry B. Gray
- Beckman Institute, California
Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
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28
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Pauszek RF, Stanley RJ. A "how-to" guide to the stark spectroscopy of flavins and flavoproteins. Methods Mol Biol 2014; 1146:443-466. [PMID: 24764101 DOI: 10.1007/978-1-4939-0452-5_17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Flavins and flavoproteins have been studied by a plethora of spectroscopic techniques. Beginning with the characterization of DNA photolyases and the discovery of the diversity of roles played by excited-state flavins in photobiology, the characterization of the electronic excited state of flavins has become increasingly important. In this protocol, we provide a guide to using Stark spectroscopy in obtaining the degree of electronic charge redistribution in simple flavins and in flavoproteins. Stark spectroscopy is technically simpler than more common approaches used to explore the structure of the excited state, considerably cheaper to implement, and yet very powerful in its scope. At the end of this guide, we present data taken on non-photobiological flavoproteins, glutathione reductase and lipoamide dehydrogenase, that suggest that Stark spectroscopy is a unique way to elucidate the electrostatic environment that the flavin cofactor experiences bound inside the protein.
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Affiliation(s)
- Raymond F Pauszek
- Department of Chemistry, Temple University, 250B Beury Hall, 1901N. 13th Street, Philadelphia, PA, 19122, USA
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29
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Pauszek RF, Kodali G, Caldwell ST, Fitzpatrick B, Zainalabdeen NY, Cooke G, Rotello VM, Stanley RJ. Excited state charge redistribution and dynamics in the donor-π-acceptor flavin derivative ABFL. J Phys Chem B 2013; 117:15684-94. [PMID: 24020957 DOI: 10.1021/jp406420h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chromophores containing a donor-π-acceptor (D-π-A) motif have been shown to exhibit many interesting photophysical properties. The lowest electronic transition of a flavin derivative containing this motif, azobenzylflavin (ABFL), has previously been shown to be highly sensitive to solvent environment and hydrogen bonding ligands. To better understand this sensitivity, we have investigated the excited state charge redistribution and dynamics of ABFL in a low-dielectric, non-hydrogen bonding solvent by steady-state Stark and femtosecond optical transient absorption spectroscopies. The Stark measurements reveal the difference dipole moment, Δμ01, between the ground and first excited states to be 22.3 ± 0.9 D. The direction of Δμ01 in the molecular frame was assigned with the aid of TD-DFT and finite field calculations, verifying the hypothesis that electron density moves from the diethylaniline donor to the flavin acceptor in the excited state. The magnitude of the difference dipole moment was used to estimate the hyperpolarizability of ABFL, β0 = 720 × 10(-30) esu. Subsequent excited state decay via charge recombination was shown to take place in a few picoseconds. The data was best fit to a kinetic model composed of a sub-picosecond internal conversion step from S2→S1, followed by a 5 ps decay to the ground state. A competing process involving formation of an additional long-lived state from S1 was also observed. Cyclic voltammetry shows one oxidation and two reduction waves and is completely reversible. This analysis lays the groundwork for developing new flavin dyads with the desired excited electronic state properties for applications such as nonlinear optical devices, molecular electronics applications, or dye-sensitized solar cells.
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Affiliation(s)
- Raymond F Pauszek
- Department of Chemistry, Temple University , Philadelphia, Pennsylvania 19122, United States
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30
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Lüdemann G, Woiczikowski PB, Kubař T, Elstner M, Steinbrecher TB. Charge transfer in E. coli DNA photolyase: understanding polarization and stabilization effects via QM/MM simulations. J Phys Chem B 2013; 117:10769-78. [PMID: 23964783 DOI: 10.1021/jp406319b] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We study fast hole transfer events in E. coli DNA photolyase, a key step in the photoactivation process, using a multiscale computational method that combines nonadiabatic propagation schemes and linear-scaling quantum chemical methods with molecular mechanics force fields. This scheme allows us to follow the time-dependent evolution of the electron hole in an unbiased fashion; that is, no assumptions about hole wave function localization, time scale separation, or adiabaticity of the process have to be made beforehand. DNA photolyase facilitates an efficient long-range charge transport between its flavin adenine dinucleotide (FAD) cofactor and the protein surface via a chain of evolutionary conserved Trp residues on the sub-nanosecond time scale despite the existence of multiple potential trap states. By including a large number of aromatic residues along the charge transfer pathway into the quantum description, we are able to identify the main pathway among alternative possible routes. The simulations show that charge transfer, which is extremely fast in this protein, occurs on the same time scale as the protein response to the electrostatic changes; that is, time-scale separation as often presupposed in charge transfer studies seems to be inappropriate for this system. Therefore, coupled equations of motion, which propagate electrons and nuclei simultaneously, appear to be necessary. The applied computational model is shown to capture the essentials of the reaction kinetics and thermodynamics while allowing direct simulations of charge transfer events on their natural time scale.
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Affiliation(s)
- Gesa Lüdemann
- Department for Theoretical Chemical Biology, Institute for Physical Chemistry, Karlsruhe Institute for Technology , Kaiserstr. 12, 76131 Karlsruhe, Germany
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31
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Zhang S, Zhang Y, Ma X, Lu L, He Y, Deng Y. Benzonitrile as a Probe of Local Environment in Ionic Liquids. J Phys Chem B 2013; 117:2764-72. [DOI: 10.1021/jp312251q] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shiguo Zhang
- Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Yan Zhang
- Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Xiangyuan Ma
- Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Liujin Lu
- Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Yude He
- Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
| | - Youquan Deng
- Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
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32
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Abstract
Biological redox machines require efficient transfer of electrons and holes for function. Reactions involving multiple tunneling steps, termed "hopping," often promote charge separation within and between proteins that is essential for energy storage and conversion. Here we show how semiclassical electron transfer theory can be extended to include hopping reactions: graphical representations (called hopping maps) of the dependence of calculated two-step reaction rate constants on driving force are employed to account for flow in a rhenium-labeled azurin mutant as well as in two structurally characterized redox enzymes, DNA photolyase and MauG. Analysis of the 35 Å radical propagation in ribonucleotide reductases using hopping maps shows that all tyrosines and tryptophans on the radical pathway likely are involved in function. We suggest that hopping maps can facilitate the design and construction of artificial photosynthetic systems for the production of fuels and other chemicals.
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Affiliation(s)
- Jeffrey J Warren
- Beckman Institute, California Institute of Technology, Mail Code 139-74, Pasadena, CA 91125, USA
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33
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Chosrowjan H, Taniguchi S, Wongnate T, Sucharitakul J, Chaiyen P, Tanaka F. Conformational heterogeneity in pyranose 2-oxidase from Trametes multicolor revealed by ultrafast fluorescence dynamics. J Photochem Photobiol A Chem 2012. [DOI: 10.1016/j.jphotochem.2011.11.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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34
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Kodali G, Narayanan M, Stanley RJ. Excited-state electronic properties of 6-methylisoxanthopterin (6-MI): an experimental and theoretical study. J Phys Chem B 2012; 116:2981-9. [PMID: 22276652 DOI: 10.1021/jp2110083] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
6-Methylisoxanthopterin (6-MI) is a pteridine-based guanine analog that has a red-shifted absorption and high fluorescence quantum yield. Its Watson-Crick base-pairing and base stacking properties are similar to guanine. The fluorescence quantum yield of 6-MI is sensitive to its nearest neighbors and base stacking, making it a very useful real-time probe of DNA structure. The fundamental photophysics underlying this fluorescence quenching by base stacking is not well understood. We have explored the excited-state electronic structure of the 6-MI in frozen 77 K LiCl glasses using Stark spectroscopy. These measurements yielded the direction and degree of charge redistribution for the S(0)→S(1) transition as manifested in the difference dipole moment, Δμ(01), and difference static polarizability, TrΔα. TDDFT (time-dependent density functional theory) was employed to calculate the transition energy, oscillator strength, and the dipole moments of the ground and lowest optically bright excited state of 6-MI (S(0)→S(1)). The direction of Δμ(01) was assigned in the molecular frame based on the Stark data and calculations. These results suggest that the C4═O and C2-NH(2) groups are electron-deficient in the excited state, a very different outcome compared with guanine. This implies that Watson-Crick hydrogen bonding in 6-MI may be modulated by absorption of a photon so as to strengthen base pairing, if only transiently. Solvatochromism was also obtained for the absorption and emission spectra of 6-MI in various solvents and compared with the Stark spectroscopic results using both the Lippert-Mataga and Bakhshiev models.
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Affiliation(s)
- Goutham Kodali
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA
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35
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Woiczikowski PB, Steinbrecher T, Kubař T, Elstner M. Nonadiabatic QM/MM Simulations of Fast Charge Transfer in Escherichia coli DNA Photolyase. J Phys Chem B 2011; 115:9846-63. [DOI: 10.1021/jp204696t] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paul Benjamin Woiczikowski
- Department for Theoretical Chemical Biology, Institute for Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstrasse 12, D-76131 Karlsruhe, Germany
| | - Thomas Steinbrecher
- Department for Theoretical Chemical Biology, Institute for Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstrasse 12, D-76131 Karlsruhe, Germany
| | - Tomáš Kubař
- Department for Theoretical Chemical Biology, Institute for Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstrasse 12, D-76131 Karlsruhe, Germany
| | - Marcus Elstner
- Department for Theoretical Chemical Biology, Institute for Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstrasse 12, D-76131 Karlsruhe, Germany
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36
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Cui D, Koder RL, Dutton PL, Miller AF. 15N solid-state NMR as a probe of flavin H-bonding. J Phys Chem B 2011; 115:7788-98. [PMID: 21619002 DOI: 10.1021/jp202138d] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Flavins mediate a wide variety of chemical reactions in biology. To learn how one cofactor can be made to execute different reactions in different enzymes, we are developing solid-state NMR (SSNMR) to probe the flavin electronic structure, via the (15)N chemical shift tensor principal values (δ(ii)). We find that SSNMR has superior responsiveness to H-bonds, compared to solution NMR. H-bonding to a model of the flavodoxin active site produced an increase of 10 ppm in the δ(11) of N5, although none of the H-bonds directly engage N5, and solution NMR detected only a 4 ppm increase in the isotropic chemical shift (δ(iso)). Moreover SSNMR responded differently to different H-bonding environments, as H-bonding with water caused δ(11) to decrease by 6 ppm, whereas δ(iso) increased by less than 1 ppm. Our density functional theoretical (DFT) calculations reproduce the observations, validating the use of computed electronic structures to understand how H-bonds modulate the flavin's reactivity.
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Affiliation(s)
- Dongtao Cui
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, United States
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37
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Brettel K, Byrdin M. Reaction mechanisms of DNA photolyase. Curr Opin Struct Biol 2010; 20:693-701. [PMID: 20705454 DOI: 10.1016/j.sbi.2010.07.003] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 07/08/2010] [Indexed: 10/19/2022]
Abstract
DNA photolyase uses visible light and a fully reduced flavin cofactor FADH(-) to repair major UV-induced lesions in DNA, the cyclobutane pyrimidine dimers (CPDs). Electron transfer from photoexcited FADH(-) to CPD, splitting of the two intradimer bonds, and back electron transfer to the transiently formed flavin radical FADH° occur in overall 1ns. Whereas the kinetics of FADH° was resolved, the DNA-based intermediates escaped unambiguous detection yet. Another light reaction, named photoactivation, reduces catalytically inactive FADH° to FADH(-) without implication of DNA. It involves electron hopping along a chain of three tryptophan residues in 30ps, as elucidated in detail by transient absorption spectroscopy. The same triple tryptophan chain is found in cryptochrome blue-light photoreceptors and may be involved in their primary photoreaction.
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Affiliation(s)
- Klaus Brettel
- CEA, IBITECS, Laboratoire de Photocatalyse et Biohydrogène, 91191 Gif-sur-Yvette, France.
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38
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Bonetti C, Stierl M, Mathes T, van Stokkum IHM, Mullen KM, Cohen-Stuart TA, van Grondelle R, Hegemann P, Kennis JTM. The role of key amino acids in the photoactivation pathway of the Synechocystis Slr1694 BLUF domain. Biochemistry 2009; 48:11458-69. [PMID: 19863128 DOI: 10.1021/bi901196x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BLUF (blue light sensing using FAD) domains belong to a novel group of blue light sensing receptor proteins found in microorganisms. We have assessed the role of specific aromatic and polar residues in the Synechocystis Slr1694 BLUF protein by investigating site-directed mutants with substitutions Y8W, W91F, and S28A. The W91F and S28A mutants formed the red-shifted signaling state upon blue light illumination, whereas in the Y8W mutant, signaling state formation was abolished. The W91F mutant shows photoactivation dynamics that involve the successive formation of FAD anionic and neutral semiquinone radicals on a picosecond time scale, followed by radical pair recombination to result in the long-lived signaling state in less than 100 ps. The photoactivation dynamics and quantum yield of signaling state formation were essentially identical to those of wild type, which indicates that only one significant light-driven electron transfer pathway is available in Slr1694, involving electron transfer from Y8 to FAD without notable contribution of W91. In the S28A mutant, the photoactivation dynamics and quantum yield of signaling state formation as well as dark recovery were essentially the same as in wild type. Thus, S28 does not play an essential role in the initial hydrogen bond switching reaction in Slr1694 beyond an influence on the absorption spectrum. In the Y8W mutant, two deactivation branches upon excitation were identified: the first involves a neutral semiquinone FADH(*) that was formed in approximately 1 ps and recombines in 10 ps and is tentatively assigned to a FADH(*)-W8(*) radical pair. The second deactivation branch forms FADH(*) in 8 ps and evolves to FAD(*-) in 200 ps, which recombines to the ground state in about 4 ns. In the latter branch, W8 is tentatively assigned as the FAD redox partner as well. Overall, the results are consistent with a photoactivation mechanism for BLUF domains where signaling state formation proceeds via light-driven electron and proton transfer from Y8 to FAD, followed by a hydrogen bond rearrangement and radical pair recombination.
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Affiliation(s)
- Cosimo Bonetti
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, VU University, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands
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39
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Byrdin M, Lukacs A, Thiagarajan V, Eker APM, Brettel K, Vos MH. Quantum Yield Measurements of Short-Lived Photoactivation Intermediates in DNA Photolyase: Toward a Detailed Understanding of the Triple Tryptophan Electron Transfer Chain. J Phys Chem A 2009; 114:3207-14. [DOI: 10.1021/jp9093589] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Martin Byrdin
- CEA, IBITECS, Laboratoire de Photocatalyse et Biohydrogène, Gif sur Yvette, F-91191, France, CNRS, URA2096, Gif sur Yvette, F-91191, France, Laboratoire d’Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France, INSERM U696, F-91128 Palaiseau, France, and Department of Cell Biology and Genetics, Medical Genetics Centre, Erasmus University Medical Centre, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Andras Lukacs
- CEA, IBITECS, Laboratoire de Photocatalyse et Biohydrogène, Gif sur Yvette, F-91191, France, CNRS, URA2096, Gif sur Yvette, F-91191, France, Laboratoire d’Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France, INSERM U696, F-91128 Palaiseau, France, and Department of Cell Biology and Genetics, Medical Genetics Centre, Erasmus University Medical Centre, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Viruthachalam Thiagarajan
- CEA, IBITECS, Laboratoire de Photocatalyse et Biohydrogène, Gif sur Yvette, F-91191, France, CNRS, URA2096, Gif sur Yvette, F-91191, France, Laboratoire d’Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France, INSERM U696, F-91128 Palaiseau, France, and Department of Cell Biology and Genetics, Medical Genetics Centre, Erasmus University Medical Centre, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - André P. M. Eker
- CEA, IBITECS, Laboratoire de Photocatalyse et Biohydrogène, Gif sur Yvette, F-91191, France, CNRS, URA2096, Gif sur Yvette, F-91191, France, Laboratoire d’Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France, INSERM U696, F-91128 Palaiseau, France, and Department of Cell Biology and Genetics, Medical Genetics Centre, Erasmus University Medical Centre, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Klaus Brettel
- CEA, IBITECS, Laboratoire de Photocatalyse et Biohydrogène, Gif sur Yvette, F-91191, France, CNRS, URA2096, Gif sur Yvette, F-91191, France, Laboratoire d’Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France, INSERM U696, F-91128 Palaiseau, France, and Department of Cell Biology and Genetics, Medical Genetics Centre, Erasmus University Medical Centre, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Marten H. Vos
- CEA, IBITECS, Laboratoire de Photocatalyse et Biohydrogène, Gif sur Yvette, F-91191, France, CNRS, URA2096, Gif sur Yvette, F-91191, France, Laboratoire d’Optique et Biosciences, CNRS, Ecole Polytechnique, F-91128 Palaiseau, France, INSERM U696, F-91128 Palaiseau, France, and Department of Cell Biology and Genetics, Medical Genetics Centre, Erasmus University Medical Centre, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
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40
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Kodali G, Kistler KA, Narayanan M, Matsika S, Stanley RJ. Change in Electronic Structure upon Optical Excitation of 8-Vinyladenosine: An Experimental and Theoretical Study. J Phys Chem A 2009; 114:256-67. [DOI: 10.1021/jp908055h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Goutham Kodali
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Kurt A. Kistler
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Madhavan Narayanan
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Spiridoula Matsika
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
| | - Robert J. Stanley
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122
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