SOLVENT SUPPRESSION WITH SYMMETRICALLY-SHIFTED PULSES

Symmetrically-shifted shaped pulses are used to suppress large solvent resonances such as water while allowing the observation of protons exchanging with, or buried under, the water resonance. Symmetrically-shifted pulses form a family of pulses that have been optimized for non-excitation of the water resonance and can be seen as having historical precedence in, and many of the properties of, long rectangular pulses and binomial sequences. Linear prediction software coupled with data shifting is used to eliminate the undesirable frequency-dependent phase and baseline problems normally associated with pulses or excitation schemes of this length. Zero-frequency solvent subtraction is also described. Results are illustrated for DNA and protein samples in 90% water.