Fig. 3.

(a) 2D ¹⁵N–¹³C correlation spectrum of microcrystalline, uniformly ¹⁵N, ¹³C-labeled GB1, obtained at 14.1 T using the pulse sequence in Fig. 2a, with M = 0, N = 8, n = 16, and τ_R = 73.53 μs. Crosspeaks from which ¹⁵N-BARE decay curves were extracted are indicated with their residue-specific assignments. (b) Representative ¹⁵N-BARE decay curves. Solid and dashed curves are simulations using backbone torsion angles from PDB 2GI9, before (solid) and after (dashed) refinement against the ¹⁵N-BARE and ¹³C-BARE data as described in the text. Experimental data and simulations are normalized to 1.00 at zero evolution time. (c) Signal decay at the maximum evolution time for all residues with measureable ¹⁵N-BARE curves. Thin and thick bars indicate β-strand and α-helix segments in GB1, respectively.