Comparison of spin diffusion experiments on NAVL. Note that the peak naming convention (peaks a, b, c, d) is from the most downfield (peak a) to the most upfield (peak d). For example, the cross-peak at ω2 = 152 ppm and ω1 = 99 ppm is referred to as ac. The PDSD experiment utilized a 3 sec mixing time, the CRDSD experiment used a 15N spinlock field of 21 kHz, and the PMPT experiment used a Z-filter of 3 sec and 1H and 15N spinlock fields of 65 kHz and 55 kHz, respectively. The CRDSD and PMPT experiment used a mixing time of 10 msec. 1D sections are taken from the dotted line in the 2D spectra. All 2D spectra are shown at the same contour level, allowing for a direct comparison of peak intensities.