PFG-omega(1)-filtered TOCSY experiments for the determination of long-range heteronuclear and homonuclear coupling constants and estimation of J-coupling "crosstalk" artifacts in 2-D omega(1)-filtered "E-COSY-style" spectra

We present novel one- and two-dimensional versions of the omega(1)-filtered TOCSY experiment, These experiments utilize pulsed-field gradient techniqu es and INEPT-reverse INEPT magnetization transfer to generate heteronuclear filtering by means of coherence pathway selection. The major advantages of this approach are twofold: first, each experiment requires a reasonable nu mber of transmitter pulses, gradient pulses, and delays to implement. Secon d, the use of z-axis gradients at the beginning and termination of the puls e sequences prevents the recovery of dephased magnetization prior to FID de tection. This technique was incorporated into 1-D and 2-D omega(1),-filtere d J(XH)- and J(HH)-TOCSY-style experiments, As demonstrated on N-15-enriche d peptide samples, the use of the pulsed-held-gradient coherence selection scheme effectively filters out unwanted magnetization components, thereby i mproving the overall sensitivity of the experiments. In addition to this su ite of pulse sequences, we also present a method for correcting the reducti on in J-coupling that results from crosspeak shifting in 2-D omega(1),-filt ered E. COSY-style spectra, This correction is applicable to both Lorentzia n and Gaussian 2-D crosspeak lineshapes. (C) 1999 Academic Press.