Articles | Volume 4, issue 1
https://doi.org/10.5194/mr-4-1-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/mr-4-1-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
12 Jan 2023
Research article |
| 12 Jan 2023
| 12 Jan 2023
Intermolecular contributions, filtration effects and signal composition of SIFTER (single-frequency technique for refocusing)
Agathe Vanas
Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
Janne Soetbeer
Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
Frauke Diana Breitgoff
Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
Henrik Hintz
Department of Chemistry, Bielefeld University, Universitätsstrasse 25,
33615 Bielefeld, Germany
Muhammad Sajid
Department of Chemistry, Bielefeld University, Universitätsstrasse 25,
33615 Bielefeld, Germany
Yevhen Polyhach
Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
Adelheid Godt
Department of Chemistry, Bielefeld University, Universitätsstrasse 25,
33615 Bielefeld, Germany
Gunnar Jeschke
Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
Maxim Yulikov
CORRESPONDING AUTHOR
Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
Daniel Klose
CORRESPONDING AUTHOR
Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
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Measuring distances between unpaired electron spins is an important application of electron paramagnetic resonance. The longest distance that is accessible is limited by the phase memory time of the electron spins. Here we show that strong continuous microwave irradiation can significantly slow down relaxation. Additionally, we introduce a phase-modulation scheme that allows measurement of the distance during the irradiation. Our approach could thus significantly extend the accessible distances.
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Quantification of heterogeneous systems such as unstructured or semi-structured (bio)macromolecules is an important but challenging task. Pulse EPR methods can contribute by characterizing the local nuclear environment of a spin centre. Here, we provide a detailed assessment of a pulse EPR technique derived from a RIDME experiment. We review the theoretical principles, discuss the data analysis and demonstrate an application to a spin-labeled macromolecule supported by in silico modelling.
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Electron spins sense their environment via magnetic interactions. An important contribution stems from nuclear spins in their vicinity. They cause loss of coherence and thus reduce resolution of spectra obtained by experiments on electron spins and the efficiency of transferring electron-spin magentization to other nuclear spins. Here we study how protons in trityl radicals contribute to coherence loss. Such coherence loss is slower in the presence of a strong microwave field.
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We show the design, simulations, and experimental performance of a 35 GHz electron paramagnetic resonance (EPR) resonator based on a cylindrical cavity with 3 mm sample access. The design is robust; simple to manufacture and maintain; and, with its elevated Q value, well-suited to sensitive EPR experiments using continuous-wave or low-power pulsed excitation. Thus, we make multi-frequency EPR spectroscopy, a powerful approach to deconvolute overlapping paramagnetic species, more accessible.
Julian Stropp, Nino Wili, Niels Christian Nielsen, and Daniel Klose
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Sensitivity is often the limiting factor in ENDOR. Here, we demonstrate how using chirp radiofrequency pulses can improve ENDOR sensitivity up to 3-9-fold, with the strongest increase for broader lines often encountered in disordered solids for nuclei such as nitrogen and metals. The resulting drastic speed-up in acquisition times renders also 2D ENDOR more feasible, as we demonstrate in 2D TRIPLE showing correlations of Cu hyperfine couplings.
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Dynamic nuclear polarisation (DNP) transfers polarisation from electron to nuclear spins. This is usually combined with direct detection of the latter. Here, we show that it is possible to reverse the transfer at 1.2 T. This allows us to investigate the spin dynamics of nuclear spins close to electrons – something that is notoriously difficult with established methods. We expect reverse DNP to be useful in the study of spin diffusion or as a building block for more elaborate pulse sequences.
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Dipolar electron paramagnetic resonance spectroscopy methods such as DEER provide data on how proteins change shape, thus giving detailed insight into how proteins work. We present DeerLab, a comprehensive open-source software for reliably analyzing the associated data. The software implements a series of theoretical and algorithmic innovations and thereby improves the quality and reproducibility of data analysis.
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Measuring distances between unpaired electron spins is an important application of electron paramagnetic resonance. The longest distance that is accessible is limited by the phase memory time of the electron spins. Here we show that strong continuous microwave irradiation can significantly slow down relaxation. Additionally, we introduce a phase-modulation scheme that allows measurement of the distance during the irradiation. Our approach could thus significantly extend the accessible distances.
Related subject area
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Light-induced pulsed dipolar EPR spectroscopy (PDS) is an emerging field that uses photoexcited triplet states to determine distance restraints in the nanometer range. To date, light-induced PDS data have been analyzed with methods developed for techniques that do not invoke light-induced triplets. Here, we provide a new theoretical description that takes the full nature of the triplet state into account and demonstrate that it leads to more accurate fits of experimental data.
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This work examines the physics underlying double electron–electron resonance (DEER) spectroscopy, a magnetic-resonance method that provides nanoscale data about protein structure and conformations.
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Short summary
Nanometre distance measurements between spin labels by pulse EPR techniques yield structural information on the molecular level. Here, backed by experimental data, we derive a description for the total signal of the single-frequency technique for refocusing dipolar couplings (SIFTER), showing how the different spin–spin interactions give rise to dipolar signal and background – the latter has thus far been unknown.
Nanometre distance measurements between spin labels by pulse EPR techniques yield structural...
