a, Labeling a transporter at distinct sites using a spin label in case of DEER spectroscopy. b, Distance distribution calculated from spin echos in LeuT and their comparison with smFRET studies performed with fluorophores labeled at the same sites (Figures 6a, b were adapted from Mchaourab, H.S. et al., 2011 after obtaining the publisher’s consent). c, Estimation of dynamic distance measurement for fluorophores in smFRET experiments. Effective distance lies between 1 and 9 nm (Panel adapted from Lerner, E. et al., 2018 after publisher’s consent).