Observing in-phase single-quantum 15N multiplets for NH2/NH3+ groups with two-dimensional heteronuclear correlation spectroscopy

Two-dimensional (2D) F1-1H-coupled HSQC experiments provide 3:1:1:3 and 1:0:1 multiplets for AX3 and AX2 spin systems, respectively. These multiplets occur because, in addition to the 2SyHza→2SyHza process, the coherence transfers such as 2SyHza→2SyHzb occurring in t1 period provide detectable magnetization during the t2 period. Here, we present a 2D F1-1H-coupled 1H-15N heteronuclear correlation experiment that provides a 1:3:3:1 quartet for AX3 spin system and a 1:2:1 triplet for AX2. The experiment is a derivative of 2D HISQC experiment [J. Iwahara, Y.S. Jung, G.M. Clore, Heteronuclear NMR spectroscopy for lysine NH3 groups in proteins: unique effect of water exchange on 15N transverse relaxation. J. Am. Chem. Soc. 129 (2007) 2971-2980] and contains a scheme that kills anti-phase single-quantum terms generated in the t1 period. The purge scheme is essential to observe in-phase single-quantum multiplets. Applications to the NH2 and NH3+ groups in proteins are demonstrated.