WATERGATE Water suppression

WATERGATE Water suppression through gradient tailored excitation. 

WATERGATE Water suppression through gradient tailored excitation 9.4.3... 

WATERGATE water suppression by gradient tailored excitation... 

The WATERGATE (water suppression by gradient-tailored excitation) method has proved popular recently because of its high efficiency and short duration compared with the methods using PR or selective nonexcitation. The method resembles a spin-... 

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...

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...

Many different ways of effecting water suppression in the NOESY sequence have been implemented, for example, presaturation, jump and return, l-T-echo, WATERGATE, SS pulses and excitation sculpting. The basic NOESY sequence using presaturation and two variations using WATERGATE are illustrated in Fig. 24. In the basic NOESY sequence (Fig. 

Fig. 24. Various NOESY-water suppression combinations. (A) NOESY using presaturation in the relaxation delay and mixing times, ffi) WATERGATE NOESY and (C) the water flip-back WATERGATE NOESY. ...

Key Words Nuclear magnetic resonance spectroscopy, Solvent, Water suppression. Radiation damping. Demagnetization field. Bulk susceptibility effect. Presaturation, Watergate, Purge, Metabonomics. 

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.

Other even more cunning methods have been devised to suppress the water signal in samples that have a large water content (e.g., bio-fluid samples) such as the WET and the WATERGATE pulse sequences. Other sequences have been devised to cope with signals from carbon-bound hydrogens. Some of these actually collapse the 13C satellites into the main 12C peak prior to suppression. Such a sequence would be useful if you were forced to acquire a spectrum in a nondeuterated solvent. 

Fig. 10. WEX filter combined with WATERGATE suppression. The first irtl pulse in the WEX filter is selective to the water, the second is nonselective and the third can be either hard or, as shown, selective on the NH protons. t defines the mixing period. The grey gradient pulses are used for coherence selection, the mottled gradient pulse is a crusher gradient and the two gradient pulses for the WATERGATE subiuiit are coloured black. Ideally three orthogonal Sections would be used for the different gradient pulses.

Providing the echo interval in WATERGATE is kept short to minimize /-modulation, T2 relaxation and molecular diffusion effects (i.e. note the similarity with the Hahn spin-echo-based PGSE sequence in Fig. 9B), the desired resonances are retained in the spectrum with near-full intensity while the water peak should be suppressed by a factor of at least 1(1. Scalar coupling evolution can be refocused if the ir pulse in the WATERGATE sequence excites only some of the solute resonances but not the scalar coupled partners (for example amide resonances). ... 

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