Selective J-resolved spectra: a double pulsed field gradient spin-echo approach.

A simple method to obtain selective J-resolved spectra is presented, which relies on the refocusing properties of double pulsed field gradient spin-echoes and provides unambiguous assignment of the measured coupling constants. The proposed examples show how this method is of general applicability, and requires no more than a simple optimization strategy to produce artifact-free spectra. Examples of application include the determination of a small, long-range coupling constant (0.7 Hz) in trans-retinal and Halpha couplings in a tripeptide.