Water suppression pulses

Figure 2 Gradient-echo-based water suppression pulse sequences, (a) WATERGATE (b) water-flip-back (c) excitation sculpting (d and e) examples of the S pulse train that is sandwiched between the gradient echo (d) water-selective inversion...

Danielsen ER and Henriksen O (1994) Absolute quantitative proton NMR spectroscopy based on the amplitude of the local water suppression pulse. Quantification of brain water and metabolites. NMR in Biomedicine 7 311-318. 

Figure 1 Water suppression pulse sequences, where the bar symbol represents a 90° pulse (A) presaturation, (B) phase-shifted presaturation (the ratio of the duration of PR , and PRy pulses is 9 1), (C) NOESYPRESAT.

Figure 2 Water suppression pulse sequences using PFG to selectively dephase the solvent resonance, where the bar and open symbols represent 90° pulses. (A) Randomization approach to water suppression (RAW) sequence. (B) WATERGATE (the composition of the 3-9-19 pulse train and its variations are listed in Table 1). (C) Double WATERGATE echo method. It Is recommended that different echo times (/i y and different gradient strengths (G G ) are used.

Two-Dimensional Chemical Shift Correlation Using Water Suppression Pulses. One of the problems in recording 2D-NMR spectra of dilute solutions is the strength of the solvent peaks, which often mask a region... 

P.J. More, Two-dimensional chemical shift correlation using water suppression pulses, J. Magn. Resonance 56, 535 (1984) and references therein. 

Use a desired water suppression pulse program to obtain a flat baseline. In automation, the time duration for changing the sample, locking, shimming, and data collection can be within... 

Fig. 7.11 J modulation in a constant time HSQC in order to measure dipolar couplings. A Watergate pulse is introduced in order to optimize water suppression. The intensity of cross peaks is given by /(7") = C cos(nJT)exp(-T/T2) The right...

Sugar content (water suppression) 4.7 single pulse and IRFT 13 ... 

Since water protons are not bound to or nuclei, the water signal is also suppressed by the spin-lock purge pulse. In practice, the suppression of the water signal is sufficient to record HSQC spectra of protein samples dissolved in mixtures of 95% H20/5% D2O without any further water suppression scheme [12]. For optimum water suppression the carrier frequency must be at the frequency of the water resonance. On resonance, the phase of the water magnetization is not affected by imperfections of the first 180°(ff) pulse, so that no solvent magnetization ends up along the axis of the spin-lock purge pulse. 

The use of spin-lock pulses for water suppression is illustrated with the NOESY and ROESY pulse sequences (fig. 5). Using the Cartesian product operator description [9], the effect of the NOESY pulse sequence of fig. 5(A) is readily illustrated ... 

Fig. 5. Pulse sequences of NOESY and ROESY with spin-lock purge pulses for water suppression. (A) NOESY pulse sequence. The spin-lock pulses are typically of length 0.5 ms and 2 ms, and r = 1/SW, where SW is the spectral width in the acquisition dimension. Phase cycle (pi = x,—x) 4>2 = 4 x,x,—x,—x) ...

Fig. 5.4a,b. Susceptibility artifacts due to the vicinity of air in the sphenoid sinus the flow signal of ICA is lowered symmetrically on the TOF images (a), when a fat-signal suppressing water excitation pulse sequence was used. The conventional TOF/ TONE sequence shows no false vessel extinction, but a higher background signal from fat tissue (b)... 

Hwang TL, Shaka AJ, Water suppression that works. Excitation sculpting using arbitrary wave-forms and pulsed-field gradients, J. Magn. Reson., 112 275-279, 1995. 

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