Observation of Terahertz Vibrations in the Nitrogenase FeMo Cofactor by Femtosecond Pump–Probe Spectroscopy

Delfino, Ines; Cerullo, Giulio; Cannistraro, Salvatore; Manzoni, Cristian; Polli, Dario; Dapper, Christie H.; Newton, William E.; Guo, Yisong; Cramer, Stephen P.

doi:10.1002/ange.200906787

Cited by 4 publications

(6 citation statements)

References 34 publications

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“…The reactant of bipyridine or phenanthroline was not in excess. 3 was obtained from the reaction of VOSO 4 with 3 equiv of glycolic acid without the participation of N-chelated ligand. , The synthesis of 3 was at room temperature but the crystallization was found sensitive to the temperature and the concentration of the reactants. Moreover, the effects of pH variations between 4 and 6 and the ratio of V:ligand (1:2 or 1:3) seem less crucial for the formation of 3 in comparison with the cases in 1 and 2 .…”

Section: Resultsmentioning

confidence: 99%

“…The enzymes have been extensively investigated, and the structures of their catalytic active sites FeMo/V-cofactors (FeMo/V-cos) have been finally clarified as MoFe 7 S 9 C(cys)(Hhis)( R -homocit) ,− and VFe 7 S 8 C(cys)(Hhis)(XO 3 )( R -homocit) (H 4 homocit = homocitric acid, X = C or N respectively, Hcys = cysteine, C 3 H 7 NO 2 S, Hhis = histidine, C 6 H 9 N 3 O 2 ), , where homocitrates coordinate with metal Mo or V via the oxygen atoms of α-alkoxy and α-carboxy groups and have a charge of −4 . Spectroscopic studies with infrared spectroscopy (IR), , magnetic circular dichroism spectroscopy (MCD), , 19 F nuclear magnetic resonance spectroscopy ( 19 F NMR), X-ray absorption spectroscopy (XAS), − Mössbauer spectroscopy, , electron–nuclear double resonance (ENDOR), , electron spin echo envelope modulation (ESEEM), , impulsive coherent vibrational spectroscopy (ICVS), nuclear resonance vibrational spectroscopy (NRVS), , and electron paramagnetic resonance (EPR) , show a low valence and paramagnetic nature for FeMo/V-cos. The charge on FeMo-cofactor (FeMo-co) has been controversial as the metal oxidation states of FeMo-co were suggested as Mo(IV)6Fe(II)1Fe(III), Mo(IV)4Fe(II)3Fe(III), Mo(IV)2Fe(II)5Fe(III), and Mo(III)3Fe(II)4Fe(III), respectively. , In addition to the FeMo/V-cos’ central structures, the local structure about the Mo/V-homocitrato coordination is critical for the nitrogenase studies.…”

Section: Introductionmentioning

confidence: 99%

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Preliminary Assignment of Protonated and Deprotonated Homocitrates in Extracted FeMo-Cofactors by Comparisons with Molybdenum(IV) Lactates and Oxidovanadium Glycolates

Jin

Wang

et al. 2019

Inorg. Chem.

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A similar pair of protonated and deprotonated mononuclear oxidovanadium glycolates [VO(Hglyc)(phen)(H2O)]Cl·2H2O (1) and [VO(glyc)(bpy)(H2O)] (2) and a mixed-(de)protonated oxidovanadium triglycolate (NH4)2[VO(Hglyc)2(glyc)]·H2O (3) were isolated and examined. The ≡C–O(H) (≡C–OH or ≡C–O) groups coordinated to vanadium were spectroscopically and structurally identified. The glycolate in 1 features a bidentate chelation through protonated α-hydroxy and α-carboxy groups, whereas the glycolate in 2 coordinates through deprotonated α-alkoxy and α-carboxy groups. The glycolates in 3 coordinate to vanadium through α-alkoxy or α-hydroxy and α-carboxy groups, and thus has both protonated ≡C–OH and deprotonated ≡C–O bonds simultaneously. Structural investigations revealed that the longer protonated V–Oα-hydroxy bonds [2.234(2) Å and 2.244(2) Å] in 1 and 3 are close to those of FeV-co 2.17 Å1 (FeMo-co 2.17 Å2), while deprotonated V–Oα-alkoxy bonds [2, 1.930(2); 3, 1.927(2) Å] were obviously shorter. This shows a similar elongated trend as the Mo–O distances in the previously reported deprotonated vs. protonated molybdenum lactates,3 and these vanadium and molybdenum complexes have the same local V/Mo-homocitrate structures as those of FeV/Mo-cos of nitrogenases. The IR spectra of these oxidovanadium and the previously synthesized molybdenum complexes including different substituted ≡C–O(H) model compounds show red-shifts for ≡C–OH vs. ≡C–O alternation, which further assign the two IR bands of extracted FeMo-co at 1084 and 1031 cm−1 to ≡C–O and ≡C–OH vibrations respectively. Although the structural data or IR spectra for some of the previously synthesized Mo/V complexes and extracted FeMo-co were measured earlier, this is the first time that the ≡C–O(H) coordinated peaks are assigned. The overall structural and IR results well suggest the co-existence of homocitrates coordinated with α-alkoxy (deprotonated) and α-hydroxy (protonated) groups in the extracted FeMo-co.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Preliminary Assignment of Protonated and Deprotonated Homocitrates in Extracted FeMo-Cofactors by Comparisons with Molybdenum(IV) Lactates and Oxidovanadium Glycolates

Jin

Wang

et al. 2019

Inorg. Chem.

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“…The ICVS technique is a variant TA technique and has been used to study the vibrational dynamics of the mononuclear Fe site (1Fe-4S) in the Pyrococcus furiosus rubredoxin (PfRd) and the 7Fe-9S-1Mo cofactor (FeMoco) of the nitrogenase MoFe protein from Azotobacter vinelandii. [13][14][15] These studies identified key vibrational modes that are coupled to excited electronic states that participate in photoinduced electron-transfer processes.…”

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confidence: 99%

Ultrafast Charge-Transfer Dynamics in the Iron–Sulfur Complex of Rhodobacter capsulatus Ferredoxin VI

Mao

Carroll

Kim

et al. 2017

J. Phys. Chem. Lett.

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Iron-sulfur proteins play essential roles in various biological processes. Their electronic structure and vibrational dynamics are key to their rich chemistry but nontrivial to unravel. Here, the first ultrafast transient absorption and impulsive coherent vibrational spectroscopic (ICVS) studies on 2Fe-2S clusters in Rhodobacter capsulatus ferreodoxin VI are characterized. Photoexcitation initiated populations on multiple excited electronic states that evolve into each other in a long-lived charge-transfer state. This suggests a potential light-induced electron-transfer pathway as well as the possibility of using iron-sulfur proteins as photosensitizers for light-dependent enzymes. A tyrosine chain near the active site suggests potential hole-transfer pathways and affirms this electron-transfer pathway. The ICVS data revealed vibrational bands at 417 and 484 cm, with the latter attributed to an excited-state mode. The temperature dependence of the ICVS modes suggests that the temperature effect on protein structure or conformational heterogeneities needs to be considered during cryogenic temperature studies.

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“…2a shows a representative 2D ΔT / T(λ,τ) map for POXC following excitation with a 15 fs pulse tuned at 600 nm for the time delays N60 fs. The signal around zero time delay is not shown since it is dominated by the non-resonant response of the buffer solution, which vanishes when pump and probe are well separated temporally [15,26]. For time delays longer than 60 fs the solvent response vanishes and we therefore detect the pure enzyme signal.…”

Section: Resultsmentioning

confidence: 91%

Ultrafast excited-state charge-transfer dynamics in laccase type I copper site

Delfino

Viola

Cerullo

et al. 2015

Biophysical Chemistry

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• T1Cu MLCT in POXC is described by ultrafast pump-probe spectroscopy • The first step of the charge-transfer in POXC occurs within 375 fs • Ground-state coherent oscillations are compared to Resonance Raman features • The trigonal T1 Cu site geometry hypothesized for POXC is confirmed by the results G R A P H I C A L A B S T R A C Ta b s t r a c t a r t i c l e i n f o Femtosecond pump-probe spectroscopy was used to investigate the excited state dynamics of the T1 copper site of laccase from Pleurotus ostreatus, by exciting its 600 nm charge transfer band with a 15-fs pulse and probing over a broad range in the visible region. The decay of the pump-induced ground-state bleaching occurs in a single step and is modulated by clearly visible oscillations. Global analysis of the two-dimensional differential transmission map shows that the excited state exponentially decays with a time constant of 375 fs, thus featuring a decay rate slower than those occurring in quite all the investigated T1 copper site proteins. The ultrashort pump pulse induces a vibrational coherence in the protein, which is mainly assigned to ground state activity, as expected in a system with fast excited state decay. Vibrational features are discussed also in comparison with the traditional resonance Raman spectrum of the enzyme. The results indicate that both excited state dynamics and vibrational modes associated with the T1 Cu laccase charge transfer have main characteristics similar to those of all the T1 copper site-containing proteins. On the other hand, the differences observed for laccase from P. ostreatus further confirm the peculiar hypothesized trigonal T1 Cu site geometry.

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Observation of Terahertz Vibrations in the Nitrogenase FeMo Cofactor by Femtosecond Pump–Probe Spectroscopy

Cited by 4 publications

References 34 publications

Preliminary Assignment of Protonated and Deprotonated Homocitrates in Extracted FeMo-Cofactors by Comparisons with Molybdenum(IV) Lactates and Oxidovanadium Glycolates

Preliminary Assignment of Protonated and Deprotonated Homocitrates in Extracted FeMo-Cofactors by Comparisons with Molybdenum(IV) Lactates and Oxidovanadium Glycolates

Ultrafast Charge-Transfer Dynamics in the Iron–Sulfur Complex of Rhodobacter capsulatus Ferredoxin VI

Ultrafast excited-state charge-transfer dynamics in laccase type I copper site

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