Tm filtering by 1 H-methyl labeling in a deuterated protein for pulsed double electron-electron resonance EPR

Chem Commun (Camb). 2020 Sep 17;56(74):10890-10893. doi: 10.1039/d0cc04369a.


Modulating the phase-memory relaxation time (Tm) of a spin label by introducing 1H-methyl groups in a perdeuterated protein background is used in DEER experiments to assign interactions in multimodal P(r) distributions. Proof of principle is demonstrated using Protein A where one nitroxide label occupies two distinct regions of conformational space. The presence of a single protonated methyl group in close proximity (4-8 Å) to only one of the two nitroxide rotamer ensembles results in a selective and substantial decrease in Tm, manifested by differential decay of the peak intensities in the bimodal P(r) distance distribution as a function of the total dipolar evolution time. This form of Tm filtering will facilitate DEER structural analysis of biomolecular systems with three spin labels, including complexes involving multimeric proteins.

MeSH terms

  • Electron Spin Resonance Spectroscopy
  • Electrons*
  • Protons*
  • Spin Labels
  • Staphylococcal Protein A / chemistry*
  • Time Factors


  • Protons
  • Spin Labels
  • Staphylococcal Protein A