3.2.3. 2D 1H-15N NMR Spectra Collection and Processing

The sofast 2D 1H-15N HMQC spectra shown in Figure 5 were collected using an 850 MHz spectrometer. The Bruker pulse sequence of *sfhmqcf3gpph* was applied. The spectral width for the 1H dimension was 14 ppm with the carrier frequency centered at 4.8 ppm. The spectral width for the 15N dimension was 35 ppm with the carrier frequency centered at 117 ppm. The complex points of 1784 and 200 were acquired for the 1H and 15N dimensions, respectively. The resulting acquisition times for 1H and 15N spins were 75 and 33 ms, respectively. The 15N decoupling sequence was GARP with a radio frequency field strength of 1.1 kHz. The coupling constant 1JHN was set to 100 Hz as a compromise between efficient INEPT transfer and T2 signal loss. The recycle delay was 0.1 s. The number of scans was 2000 and the total experimental time was 23 h. The 1H-15N spectra were processed in a manner similar to the 1H-13C spectra, except for the zero filling of <sup>4096</sup> × 1024 real data points applied to the 1H and 15N dimensions.
