Pulse EPR

Stoll, Stefan

doi:10.1002/9780470034590.emrstm1510

Cited by 14 publications

(10 citation statements)

References 11 publications

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“…Importantly, under microwave pulses of various power and length, MgHOTP exhibits oscillations of spin orientations with frequencies ω Rabi that are linearly dependent on B 1 (Figures b and S12), providing key evidence that radicals in MgHOTP are suitable for single-qubit quantum gate operations . More practically, an electron spin qubit must also possess long spin–lattice relaxation time ( T 1 ) and phase memory time ( T m ) to ensure sufficient duration of its polarization and coherence. , To measure T 1 and T m , we employed inversion recovery and Hahn echo decay pulse sequences, respectively, on dry powders of MgHOTP. Depending on the synthetic conditions of each batch of MgHOTP, these measurements gave room-temperature values of T 1 ranging from 9.48 to 21.34 μs and T m ranging from 153 to 239 ns at 296 K (Figures c,d and S13), qualifying MgHOTP as a potential candidate for quantum sensing of chemical analytes under ambient conditions.…”

Section: Resultsmentioning

confidence: 99%

“…Notably, CP-ESEEM with MgHOTP enables quantitative detection of even lower concentrations of Li + because the ESEEM signal from 7 Li can be referenced to that of an internal standard, here 1 H (see theoretical analysis in the Supporting Information). , We took advantage of the narrow line width of MgHOTP (Figures a and S25) and adopted an optimal CP-ESEEM delay time τ = 120 ns, which gives maximum modulation depth from 7 Li (Figures c and S26–S28). With these parameters, all CP-ESEEM measurements display 1 H peaks with the same line shape for any [Li + ] in the range 1 × 10 –4 –2 mol/L (Figure d), showing minimal influence of 7 Li nuclear spins on the radical– 1 H interactions.…”

Section: Resultsmentioning

confidence: 99%

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Room-Temperature Quantitative Quantum Sensing of Lithium Ions with a Radical-Embedded Metal–Organic Framework

et al. 2022

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Recent advancements in quantum sensing have sparked transformative detection technologies with high sensitivity, precision, and spatial resolution. Owing to their atomic-level tunability, molecular qubits and ensembles thereof are promising candidates for sensing chemical analytes. Here, we show quantum sensing of lithium ions in solution at room temperature with an ensemble of organic radicals integrated in a microporous metal–organic framework (MOF). The organic radicals exhibit electron spin coherence and microwave addressability at room temperature, thus behaving as qubits. The high surface area of the MOF promotes accessibility of the guest analytes to the organic qubits, enabling unambiguous identification of lithium ions and quantitative measurement of their concentration through relaxometric and hyperfine spectroscopic methods based on electron paramagnetic resonance (EPR) spectroscopy. The sensing principle presented in this work is applicable to other metal ions with nonzero nuclear spin.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Room-Temperature Quantitative Quantum Sensing of Lithium Ions with a Radical-Embedded Metal–Organic Framework

et al. 2022

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“…However, it has been shown that the superposition of nuclear frequencies does not lead to large errors in the determination of D ( Fursman and Hore, 1999 ). 4) The typical deadtime of a pulsed EPR spectrometer ( Stoll, 2017 ) precludes detection of the early response to the application of the OOP ESEEM pulse sequence (typically ≈100 ns after the last microwave pulse). Hence, one has to cope with a “truncated” time trace.…”

Section: Resultsmentioning

confidence: 99%

OOP-ESEEM Spectroscopy: Accuracies of Distances of Spin-Correlated Radical Pairs in Biomolecules

Said

Weber

Schleicher

2022

Front. Mol. Biosci.

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In addition to the commonly used electron–electron double resonance (ELDOR) technique, there are several other electron paramagnetic resonance (EPR) methods by which structure information can be obtained by exploiting the dipolar coupling between two radicals based on its characteristic r−3 dependence. In this contribution, we explore the potential of out-of-phase-electron-spin echo envelope modulation (OOP-ESEEM) spectroscopy to collect accurate distance information in photo-sensitive (bio) molecules. Although the method has already been applied to spin-correlated radical pairs in several classes of light-active proteins, the accuracy of the information obtained has not yet been extensively evaluated. To do this in a system-independent fashion, OOP-ESEEM time traces simulated with different values of the dipolar and exchange couplings were generated and analyzed in a best-possible way. Excellent agreement between calculated and numerically fitted values over a wide range of distances (between 15 and 45 Å) was obtained. Furthermore, the limitations of the method and the dependence on various experimental parameters could be evaluated.

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“…The radical signature is clearly asymmetric because the electron-Zeeman anisotropy, determined by the g -matrix of FADH • , exceeds the inhomogeneous spectral linewidth. By recording ENDOR spectra at different magnetic field positions in the resonance range one can now detect molecules with particular orientations with respect to the direction of the external magnetic field vector B 0 29 , 38 , 39 . For example, recording ENDOR at a magnetic-field strength B 0 corresponding to the principal value g Z of FADH • reveals hyperfine data of those molecules whose principal Z axis is aligned parallel to B 0 thus resembling data from a partially oriented sample.…”

Section: Resultsmentioning

confidence: 99%

Selective 13C labelling reveals the electronic structure of flavocoenzyme radicals

Schleicher

Rein

Illarionov

et al. 2021

Sci Rep

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Flavocoenzymes are nearly ubiquitous cofactors that are involved in the catalysis and regulation of a wide range of biological processes including some light-induced ones, such as the photolyase-mediated DNA repair, magnetoreception of migratory birds, and the blue-light driven phototropism in plants. One of the factors that enable versatile flavin-coenzyme biochemistry and biophysics is the fine-tuning of the cofactor’s frontier orbital by interactions with the protein environment. Probing the singly-occupied molecular orbital (SOMO) of the intermediate radical state of flavins is therefore a prerequisite for a thorough understanding of the diverse functions of the flavoprotein family. This may be ultimately achieved by unravelling the hyperfine structure of a flavin by electron paramagnetic resonance. In this contribution we present a rigorous approach to obtaining a hyperfine map of the flavin’s chromophoric 7,8-dimethyl isoalloxazine unit at an as yet unprecedented level of resolution and accuracy. We combine powerful high-microwave-frequency/high-magnetic-field electron–nuclear double resonance (ENDOR) with 13C isotopologue editing as well as spectral simulations and density functional theory calculations to measure and analyse 13C hyperfine couplings of the flavin cofactor in DNA photolyase. Our data will provide the basis for electronic structure considerations for a number of flavin radical intermediates occurring in blue-light photoreceptor proteins.

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Pulse EPR

Cited by 14 publications

References 11 publications

Room-Temperature Quantitative Quantum Sensing of Lithium Ions with a Radical-Embedded Metal–Organic Framework

Room-Temperature Quantitative Quantum Sensing of Lithium Ions with a Radical-Embedded Metal–Organic Framework

OOP-ESEEM Spectroscopy: Accuracies of Distances of Spin-Correlated Radical Pairs in Biomolecules

Selective 13C labelling reveals the electronic structure of flavocoenzyme radicals

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