Háskóli ÍslandsUniversity of IcelandJagtap, A. P.Krstic, I.Kunjir, N. C.Hänsel, R.Prisner, Thomas F.Sigurdsson, Snorri2020-08-102020-08-102014-11-20A. P. Jagtap, I. Krstic, N. C. Kunjir, R. Hänsel, T. F. Prisner & S. Th. Sigurdsson (2015) Sterically shielded spin labels for in-cell EPR spectroscopy: Analysis of stability in reducing environment, Free Radical Research, 49:1, 78-85DOI: 10.3109/10715762.2014.9794091071-57621029-2470 (eISSN)https://hdl.handle.net/20.500.11815/1954Post-print (lokagerð höfundar)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.78-85eninfo:eu-repo/semantics/openAccessNitroxide reductionAminoxyl radicalRadical stabilitySpin labelingTrityl radicalLitrófsgreiningEfnagreininginfo:eu-repo/semantics/articleFree Radical Research10.3109/10715762.2014.979409