Unfortunately, the ZQc term will also survive the phase cycling, and lead to dispersive antiphase signals at the diagonal and at the cross-peak position between two protons with a scalar coupling These signals can feign a NOESY cross-peak even in the absence of an NOE However, unlike the in-phase NOE cross-peaks, they do not have a net integral(antiphase! ) so that they can be distinguished from real NOESY cross-peaks(but only if really the whole peak area is integrated, including the wide dispersive tails of the ZQc peaks! ) Of course, ZQC peaks do not interfere with an noe between two protons that do not show a mutual scalar coupling How does one now measure o, i.e., the Noe build-up rate? Let's consider the behaviour of the NOE (i.e, the integral of the NOESY cross-peak)as a function of t 1.0 0.9 0.8 0.7 0.6 0.5 0. 0.1 0.0 0 0.2 4 8 0.9 1.0 Here, the build-up of two NOEs is shown(solid lines), with the o of the first one twice as large as the second one. In addition, an indirect NOE (i.e, an NoE caused by the perturbation from a direct NOE) is depicted with a broken line101 Unfortunately, the ZQC term will also survive the phase cycling, and lead to dispersive antiphase signals at the diagonal and at the cross-peak position between two protons with a scalar coupling. These signals can feign a NOESY cross-peak even in the absence of an NOE! However, unlike the in-phase NOE cross-peaks, they do not have a net integral (antiphase!), so that they can be distinguished from real NOESY cross-peaks (but only if really the whole peak area is integrated, including the wide dispersive tails of the ZQC poeaks!). Of course, ZQC peaks do not interfere with an NOE between two protons that do not show a mutual scalar coupling! How does one now measure sij , i.e., the NOE build-up rate? Let's consider the behaviour of the NOE (i.e., the integral of the NOESY cross-peak) as a function of tm : 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 tm [s] NOE (arbitrary units) Here, the build-up of two NOEs is shown (solid lines), with the s of the first one twice as large as the second one. In addition, an indirect NOE (i.e., an NOE caused by the perturbation from a direct NOE) is depicted with a broken line