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1. Gd III ‐ 19 F Distance Measurements for Proteins in Cells by Electron‐Nuclear Double Resonance

   https://doi.org/10.1002/ange.202218780  

   Seal, Manas ; Zhu, Wenkai ; Dalaloyan, Arina ; Feintuch, Akiva ; Bogdanov, Alexey ; Frydman, Veronica ; Su, Xun‐Cheng ; Gronenborn, Angela M. ; Goldfarb, Daniella ( April 2023 , Angewandte Chemie)

   Studies of protein structure and dynamics are usually carried out in dilute buffer solutions, conditions that differ significantly from the crowded environment in the cell. The double electron‐electron resonance (DEER) technique can track proteins’ conformations in the cell by providing distance distributions between two attached spin labels. This technique, however, cannot access distances below 1.8 nm. Here, we show that Gd^III‐¹⁹F Mims electron‐nuclear double resonance (ENDOR) measurements can cover part of this short range. Low temperature solution and in‐cell ENDOR measurements, complemented with room temperature solution and in‐cell Gd^III‐¹⁹F PRE (paramagnetic relaxation enhancement) NMR measurements, were performed on fluorinated GB1 and ubiquitin (Ub), spin‐labeled with rigid Gd^IIItags. The proteins were delivered into human cells via electroporation. The solution and in‐cell derived Gd^III‐¹⁹F distances were essentially identical and lie in the 1–1.5 nm range revealing that both, GB1 and Ub, retained their overall structure in the Gd^IIIand¹⁹F regions in the cell.

    

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2. Gd III ‐ 19 F Distance Measurements for Proteins in Cells by Electron‐Nuclear Double Resonance

   https://doi.org/10.1002/anie.202218780  

   Seal, Manas ; Zhu, Wenkai ; Dalaloyan, Arina ; Feintuch, Akiva ; Bogdanov, Alexey ; Frydman, Veronica ; Su, Xun‐Cheng ; Gronenborn, Angela M. ; Goldfarb, Daniella ( April 2023 , Angewandte Chemie International Edition)

   Studies of protein structure and dynamics are usually carried out in dilute buffer solutions, conditions that differ significantly from the crowded environment in the cell. The double electron‐electron resonance (DEER) technique can track proteins’ conformations in the cell by providing distance distributions between two attached spin labels. This technique, however, cannot access distances below 1.8 nm. Here, we show that Gd^III‐¹⁹F Mims electron‐nuclear double resonance (ENDOR) measurements can cover part of this short range. Low temperature solution and in‐cell ENDOR measurements, complemented with room temperature solution and in‐cell Gd^III‐¹⁹F PRE (paramagnetic relaxation enhancement) NMR measurements, were performed on fluorinated GB1 and ubiquitin (Ub), spin‐labeled with rigid Gd^IIItags. The proteins were delivered into human cells via electroporation. The solution and in‐cell derived Gd^III‐¹⁹F distances were essentially identical and lie in the 1–1.5 nm range revealing that both, GB1 and Ub, retained their overall structure in the Gd^IIIand¹⁹F regions in the cell.

    

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3. On the Use of Q-Band Double Electron–Electron Resonance To Resolve the Relative Orientations of Two Double Histidine-Bound Cu 2+ Ions in a Protein

   https://doi.org/10.1021/acs.jpcb.8b07727  

   Gamble Jarvi, Austin ; Ranguelova, Kalina ; Ghosh, Shreya ; Weber, Ralph T. ; Saxena, Sunil ( November 2018 , The Journal of Physical Chemistry B)
4. Thiophene‐Based Double Helices: Radical Cations with SOMO–HOMO Energy Level Inversion †

   https://doi.org/10.1111/php.13475  

   Rajca, Andrzej ; Shu, Chan ; Zhang, Hui ; Zhang, Sheng ; Wang, Hua ; Rajca, Suchada ( July 2021 , Photochemistry and Photobiology)

   We report relatively persistent, open‐shell thiophene‐based double helices, radical cations 1^•+‐TMS₁₂and 2^•+‐TMS₈. Closed‐shell neutral double helices, 1‐TMS₁₂and 2‐TMS₈, have nearly identical first oxidation potentials,E^+/0 ≈ +1.33 V, corresponding to reversible oxidation to their radical cations. The radical cations are generated, using tungsten hexachloride in dichloromethane (DCM) as an oxidant,E^+/0 ≈ +1.56 V. EPR spectra consist of a relatively sharp singlet peak with an unusually lowg‐value of 2.001–2.002, thus suggesting exclusive delocalization of spin density over π‐conjugated system consisting of carbon atoms only. DFT computations confirm these findings, as only negligible fraction of spin density is found on sulfur and silicon atoms and the spin density is delocalized over a single tetrathiophene moiety. For radical cation, 1^•+‐TMS₁₂, energy level of the singly occupied molecular orbital (SOMO) lies below the four highest occupied molecular orbitals (HOMOs), thus indicating the SOMO–HOMO inversion (SHI) and therefore, violating the Aufbau principle. 1^•+‐TMS₁₂has a half‐life of the order of only 5 min at room temperature. EPR peak intensity of 2^•+‐TMS₈, which does not show SHI, is practically unchanged over at least 2 h.

    

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5. A 4H + /4e – Electron-Coupled-Proton Buffer Based on a Mononuclear Cu Complex

   https://doi.org/10.1021/jacs.2c05454  

   Wu, Tong ; Rajabimoghadam, Khashayar ; Puri, Ankita ; Hebert, David D. ; Qiu, Yi Lin ; Eichelberger, Sidney ; Siegler, Maxime A. ; Swart, Marcel ; Hendrich, Michael P. ; Garcia-Bosch, Isaac ( September 2022 , Journal of the American Chemical Society)