Fig. 9.

Two-dimensional PDLF pulse sequences. The pulse sequences in Fig. 1B are modified to perform PDLF class experiments by the addition of a π pulse on the ¹H channel at the same position as the ¹⁵N channel refocusing π pulse. (A) Selective magnetization transfer is performed by SAMPI4 [9,25]. (B) Magnetization transfer is performed by WIM. WIM-24 follows the same phase cycle as previously described [46], and the φ pulse is cycled between Y and –Y, and in combination with the preceding Y pulse, it cancels the spin-locked component [46]. In our experience, WIM provides higher sensitivity for magnetization transfer, while SAMPI4 provides better dipolar coupling results.