OPTIMIZATION OF THE WATER-PRESS PULSE SEQUENCE AND ITS INTEGRATION INTO PULSE SEQUENCES FOR STUDYING BIOLOGICAL MACROMOLECULES

In this paper, the recently developed ''Water-PRESS'' method of water suppression [W. S. Price and Y. Arata (1996), J. Magn. Reson. B 112, 1 90] in which homospoil pulses are used to manipulate the effects of ra diation damping on the water resonance and thereby selectively alter t he effective relaxation times of the water resonance with respect to t he solute (e.g., biological macromolecules) resonances is further deve loped and applied. In the present work, methods for optimization in te rms of degree of water suppression and in temporal terms (important fo r the application of Water-PRESS to multidimensional experiments) are considered so that recycle delays of less than 2.3 s (including the ac quisition time) are possible. Also, a simple modification which allows the observation of solute resonances with relaxation times similar to that of the water resonance is presented. Finally, the inclusion into more complicated pulse sequences is also discussed. Experimental exam ples using aqueous samples of lysozyme and immunoglobulin are given. C ompared to most other NMR water suppression techniques, this method is extremely simple to implement and optimize and does not require accur ately calibrated RF pulses or perfect lineshape. (C) 1997 Academic Pre ss.