(a) Cube representation of three-dimensional proton-detected solid-state MAS spectrum of 2H, 15N-labeled major coat protein of Pf1 bacteriophage at an MAS rate of 50 kHz obtained by using the pulse sequence in Figure 1. (b) Representative two-dimensional 1H-15N dipolar coupling - 1H chemical shift planes taken from the three-dimensional spectrum in panel (a) at 15N chemical shifts of 128.8 ppm, 114.5 ppm, and 99.7 ppm. The values for 1H-15N dipolar couplings of A46, S41, and G37 are 7.25 kHz, 7.34 kHz, and 7.36 kHz, respectively.