Fig. 2.

¹³C–¹³C side-chain correlation spectra of per-deuterated proteins. a Schematic representation of the NMR pulse sequence used to obtain ¹³C–¹³C side-chain correlation spectra. The flow of the magnetisation between ¹³C_t (blue) and ¹³C_p (red) is shown above the sequence with colour gradients. The following delays are used: Δ = 1/(4J_CC) ≈ 7.1 ms, T = 1/(2J_CC) ≈ 14.1 ms, where J_CC is the one-bond ¹³C–¹³C scalar coupling constant. Rectangular pulses are high-power and not selective, bell-shaped pulses are frequency selective (90°: white outlined, 180°: black). Deuterium, ²H, is decoupled throughout the sequence and frequency discrimination is obtained by states–TPPI of phase ϕ²¹. b Schematic representation of post-processing to obtain the decoupled spectrum. c Arginine ¹³C^δ–¹³C^γ correlation of the 18-kDa protein T4L L99A, obtained on a 1.4 mM sample at a static field of 14.1 T at 278 K in 37 min