Pure absorption phase gradient‐enhanced HMQC‐TOCSY with direct response editing

Pulsed field gradients (PFG) have the potential to revolutionize further potent, inverse‐detected structural NMR techniques by eliminating artifacts and thermal noise in data taken with very small numbers of transients. A phase‐sensitive GE (gradient‐enhanced)‐HMQC‐TOCSY experiment is reported with features which allow the discrimination (or elimination) of direct correlations relative to the relayed TOCSY responses. Sensitivity losses which arise from molecular diffusion during the course of a pulse sequence are potentially serious when field gradients are employed for solutions containing small molecules. By carefully combining phase cycling with relatively weak pulsed field gradients, it is possible both to maintain good sensitivity and to suppress completely t1 noise in GE‐HMQC‐TOCSY data acquired with only two transients per t1, increment.