Sterically shielded spin labels for in-cell EPR spectroscopy: Analysis of stability in reducing environment

A. P. Jagtap, I. Krstic, N. C. Kunjir, R. Hänsel, Thomas F. Prisner, Snorri Sigurdsson

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89 Citations (Scopus)


Electron paramagnetic resonance (EPR) spectroscopy is a powerful and widely used technique for studying structure and dynamics of biomolecules under bio-orthogonal conditions. In-cell EPR is an emerging area in this field; however, it is hampered by the reducing environment present in cells, which reduces most nitroxide spin labels to their corresponding diamagnetic N-hydroxyl derivatives. To determine which radicals are best suited for in-cell EPR studies, we systematically studied the effects of substitution on radical stability using five different classes of radicals, specifically piperidine-, imidazolidine-, pyrrolidine-, and isoindoline-based nitroxides as well as the Finland trityl radical. Thermodynamic parameters of nitroxide reduction were determined by cyclic voltammetry; the rate of reduction in the presence of ascorbate, cellular extracts, and after injection into oocytes was measured by continuous-wave EPR spectroscopy. Our study revealed that tetraethyl-substituted nitroxides are good candidates for in-cell EPR studies, in particular pyrrolidine derivatives, which are slightly more stable than the trityl radical.
Original languageEnglish
Pages (from-to)78-85
JournalFree Radical Research
Issue number1
Publication statusPublished - 20 Nov 2014

Other keywords

  • Nitroxide reduction
  • Aminoxyl radical
  • Radical stability
  • Spin labeling
  • Trityl radical
  • Litrófsgreining
  • Efnagreining


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