Characterization of ¹H-¹H distances in a uniformly ²H, ¹⁵N-labeled SH3 domain by MAS solid-state NMR spectroscopy

In this communication, we demonstrate the feasibility of obtaining long-range ¹H-¹H distance information by MAS solid-state NMR for a microcrystalline, uniformly ²H,¹⁵N-labeled sample of a SH3 domain of chicken α-spectrin. The experiments yield NOESY-type spectra and rely on the favorable dispersion of the ¹⁵N chemical shifts of the protein backbone. Perdeuteration of nonexchangeable sites is employed to simplify proton spin systems and to obtain multiple structural information. Two mixing schemes, ¹H-¹H double quantum filtered Post-C7 and ¹H spin diffusion, are implemented to obtain quantitative ¹H-¹H distance information. Post-C7 and spin diffusion cross-peak buildup rates are discussed for initial-rate fitting and in the framework of n = 0 rotational resonance (rotor driven spin diffusion), respectively. Different deuteration schemes were tested to find conditions where short-range ¹H-¹H interactions are truncated (e.g., between H^N and H^α), but long-range interactions are retained (e.g., between H^N and H^N).