hi, I'm really interesting by your bruker sequence for relaxation dispersion because I don't find any at the moment... I guess that your sequence is a constant relaxation time and relaxation compensated CPMG-HSQC. Perhaps, the CPMG frequency range is not adequate to visualize the exchange (so increased frequency can be an issue) ? Or, the error on T2 measurement can hide the exchange process (if R2ex is small) ? But my real question is : which sequence you use !! Because, there are no standart bruker sequence for relaxation dispersion...