Figure 10.

Backbone nitrogen to sidechain carbons polarization transfer: (a) ¹⁵N–¹³C δp₀ PAIN-CP at ω_r/2π = 20 kHz with p_C = p_N = 2.6 and p_H = 2.4. (b) NCACX with DCP (ω_1C/2π = 25 kHz, ω_1N/2π = 35 kHz and 100 kHz ¹H decoupling) followed by DARR (ω_1H/2π = 10 kHz) mixing at ω_r/2π = 10 kHz. (c) NCACX with DCP (ω_1C/2π = 30 kHz, ω_1N/2π = 50 kHz and 100 kHz ¹H decoupling) followed by CM₅RR (ω_1C/2π = 100 kHz, phase ±11.46°) mixing at ω_r/2π = 20 kHz. Simulations were performed at ω_0H/2π = 750 MHz. The spin system [inset of panel (a)] is extracted from the Crh x-ray structure (PDB ID: 1mu4) (Ref. ³⁰) and is composed of L63N, four aliphatic carbons L63C_α, L63C_β, L63C_γ, T62C_α (grey atoms) and the four protons mainly involved in the spin dynamics (T62H_α, L63H, L63H_α, L63H_β2, L63H_γ - white atoms). The chemical shifts are taken from the protein assignment (Ref. ³¹). L63N and the protons are irradiated on resonance. The ¹³C carrier frequency is set on resonance with L63C_α. The simulation includes typical CSA tensor parameter for nitrogen (−115 ppm, 0.2), aliphatic carbons (20–25 ppm, 0.0), and proton (5.7 ppm, 0.65).