Characterization of 1H−H 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 HN and Hα), but long-range interactions are retained (e.g., between HN and HN).