Sensitivity improvement of transverse relaxation-optimized spectroscopy

Procedures are described for significantly improving the sensitivity of the recently proposed TROSY (transverse relaxation-optimized spectroscopy) exp eriment (K. Pervushin et al., 1997, Proc. Natl. Acad. Sci. USA 94, 12366-12 371). The TROSY experiment takes advantage of destructive interference betw een 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 molec ular weight systems at very high static magnetic field strengths. A root 2 improvement in the sensitivity of the TROSY experiment is achieved by imple mentation of the PEP (preservation of equivalent pathways) scheme (J. Cavan agh and RI. Rance, 1990, J. Magn. Reson. 88, 72-85). An additional signific ant 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 betw een the coherence transfer pathways utilized in the TROSY refocusing period is shown theoretically and experimentally to give rise to additional unant icipated signals in TROSY spectra. (C) 1999 academic Press.