Abstract: Pulsed dipolar electron paramagnetic resonance (PD-EPR) is a powerful biophysical technique for probing the dynamic structures and interactions of biomacromolecules such as proteins. By measuring dipolar interactions between unpaired electrons, PD-EPR directly yields nanometer-scale distance distributions between electron spins, from which conformational transitions can be inferred by comparison under different experimental conditions. This review summarizes three major PD-EPR techniques, including double electron-electron resonance, double quantum coherence, and relaxation-induced dipolar modulation enhancement, together with commonly used spin labels and protein spin-labeling strategies, highlighting recent advances in the study of biomacromolecules and complexes.

Key words: pulsed dipolar EPR, protein dynamic structures, spin labeling, biomacromolecules, DEER