Sensitivity improvement of transverse relaxation-optimized spectroscopy

Procedures are described for significantly improving the sensitivity of the recently proposed TROSY (transverse relaxation-optimized spectroscopy) experiment (K. Pervushin et al., 1997, Proc. Natl. Acad. Sci. USA 94, 12366-12371). The TROSY experiment takes advantage of destructive interference between dipolar and chemical shift anisotropy relaxation mechanisms to achieve substantial reductions in resonance linewidths in heteronuclear correlation spectra; the effect is significant particularly for studies of large molecular weight systems at very high static magnetic field strengths. A root 2 improvement in the sensitivity of the TROSY experiment is achieved by implementation of the PEP (preservation of equivalent pathways) scheme (J. Cavanagh and RI. Rance, 1990, J. Magn. Reson. 88, 72-85). An additional significant improvement in sensitivity for N-15-labeled samples in H2O solution is realized through a simple modification of the H-1-N-15 TROSY pulse sequence to return the water magnetization to its equilibrium position (+z axis) at the beginning of the acquisition period. Relaxation-induced imbalance between the coherence transfer pathways utilized in the TROSY refocusing period is shown theoretically and experimentally to give rise to additional unanticipated signals in TROSY spectra. (C) 1999 academic Press.