ROESY with water flip back for high-field NMR of biomolecules.

We report a version of the ROESY experiment in which saturation of the water magnetization is avoided without compromising suppression of the water signal during acquisition. Field gradient and selective RF pulses are used to maintain precise control of the water magnetization throughout the experiment and avoid signal losses due to radiation damping and molecular diffusion effects. The pulse sequence includes a delay for intentional radiation damping prior to mixing period. The optimal length of this delay is field and sample dependent, but easily determined from the apparent linewidth of the water signal. NOESY and TOCSY variants of the same experiment are presented which make use of identical manipulations of the water magnetization. The three pulse sequences constitute a suite for which little parameter adjustment is required once one of the experiments has been configured.