d10: 1/[4J(N,H)] − effective gradient duration = 1.8 ms
d11: effective gradient duration, 300 μs
g1–g13: sinusoidal-shaped field gradients, ca. 0.1 T/m strength, with gradient loop counters, ring-down delays (50 μs), lock blanking and gradient coil blanking switches according to actual instrumentation used. Gradient duration and strength according to the table:

grad.	g1	g2	g3	g4	g5	g6	g7	g8	g9	g10	g11	g12	g13
[ms]	0.5	0.5	0.5	1	0.25	0.25	1.5	2.5	0.5	0.5	0.5	0.5	0.25
[%]	3	3	3	2	2	2	30	60	3	3	3	3	60.75

gradient g8 is switched in sign according to the echo/anti-echo method
¹H decoupler 90° pulse and attenuation for DIPSI-2 sequence [70 μs, 24 dB]
¹³C decoupler 180° pulse and attenuation for selective mlev-sequence [q3 Gaussian cascade, offset on CO, 256 μs, 0.5 dB]
¹⁵N decoupler 90° pulse and attenuation for GARP sequence [200 μs, 20.5 dB]
initial value for t₁ evolution: 3 μs
initial value for t₂ evolution: 3 μs
increment for t₁ evolution: 1/[2·sw1]
increment for t₂ evolution: 1/[2·sw2]
decrements for t₁ and t₂ constant time periods, be sure to set independently
ds: 32
ns: 32

5. Processing

Apply zero-filling to 128 real data points in F2 and to 128 real data points in F\ to obtain a matrix of 512128128 real data points. This will result in 8 Mb of processed real data. Application of forward linear prediction (ca. 15 coefficients) for both F2 and F; results in somewhat better resolved 3D spectra. Use Gaussian multiplication [gb = 0.1, lb = -2 Hz] in F; and a 7/3-shifted squared sinusoidal window in the other dimensions. For the data file described, extensive experimentation with different window functions may be worthwhile. Phase correction and base-line correction may be necessary for all dimensions. Further details are very dependent on the particular software you use to process such a 3D data file. Reference the indirect dimensions using the =- scale procedure described in the introduction to this chapter.

6. Result

The figures show two planes of the 3D spectrum obtained on a DRX-600 spectrometer with a multinuclear inverse z-gradient triple resonance probe-head (fixed third channel on ¹³C). As an example, in a an H,Cyg plane is chosen at dy = 120 as parameter. The NH proton of isoleucine I-36 at 5; = 6.16 reveals one positive correlation at & = 57.7, which is the C, carbon nucleus of the same amino acid. The negative correlation sig-