Nitroxides are stable organic radicals with exceptionally long lifetimes, which render them uniquely suitable as observable probes or polarising agents for spectroscopic investigation of biomolecular structure and dynamics. Spin labelling enables the study of biomolecules using electron paramagnetic resonance (EPR) spectroscopy. Here, we describe the synthesis of a spin label based on a spirocyclic pyrrolidinyl nitroxide containing an iodoacetamide moiety. The spin label was successfully used for double labelling of a calmodulin mutant, and was shown to be highly persistent under reducing conditions while maintaining excellent relaxation parameters up to a temperature of 180 K. Interspin distances measured by double electron-electron resonance (DEER) were in good agreement with the protein tertiary structure.

This dataset contains raw files and analysis reports of 1HNMR, 13CNMR of all compounds synthesized for and used in work Sigmatropic rearrangement enables access to a highly stable spirocyclic nitroxide for protein spin labelling. Moreover, copies of ATR-FTIR spectroscopy and high resolution mass spectrometry are included for novel compounds. For all nitroxides raw files of X-band CW-EPR spectra. For spin label and labelled protein Q-band EPR relaxation measurements are included. Dataset is completed with DEER experiment results for labelled protein in various temperatures and its kinetic stability based on CW-EPR spectra .

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