domain of protein G (Supplementary Fig. ). Results for CsPinA without the correction term in show systematic magnetic field dependence of τ eff values particularly around residue 50 in Fig. a. Magnetic field dependence disappears after applying the correction term (Fig. ), and residues around 50 with significant chemical exchange contributions agree with those obtained in the literature using Lipari-Szabo analysis with data recorded at 500 MHz and 700 MHz (Fig. ). This indicates that the magnetic field dependence of τ eff for CsPinA can be explained by the chemical exchange term. On the other hand, for the B3 domain of protein G, we observed systematically slightly lower τ eff values with 800 MHz than with other fields that cannot be explained by the chemical exchange correction (supplementary Fig. ). In conclusion, the magnetic field dependence of τ eff can be explained by the chemical exchange in some cases, and then used to determine the size of the chemical exchange contribution to R2 values. However, such interpretations should be done with caution because magnetic field dependence may arise also from inaccuracies in the experimental data, as indicated also by another study .