HMBC extensions and variants

Constant-time HMBC eliminating proton-proton coupling in fj 

Owing to the low-resolution conditions appropriate for most routine uses of HMBC, the constant-time approach is arguably of limited use here. However, this can prove more valuable in the band-selective experiment described below, where substantially higher/i resolution is employed and where any proton coupling structure may limit crosspeak resolution. 

F nre 6.34. The intensity of HMBC eorrelations as a fiinetion of 7xh for different values of the Alr period. Two experiments optimised for coupling constants of 8 and 4 Hz (Alr delays of 62 and 125 ms, respectively) provide reasonable sampling over the range 2-14 Hz. 

Fl are 638. The IMPEACH-MBC sequence shown without refocusing of long-range couplings. 

2VcH(max)- Gradient selection follows the echo-antiecho protocol and the gradient ratios for the low-pass filter are G2 G3 G4 = 0.075Gi 0.175Gi 0.75Gi. 

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