13C-detected through-bond correlation experiments for protein resonance assignment by ultra-fast MAS solid-state NMR

Abstract

We present two sequences which combine (1H,15N) and (15N,13C) selective cross-polarization steps with an efficient variant of the J-based homonuclear transfer scheme, in which a spin-state-selective (S3E) block is incorporated to improve both resolution and sensitivity in the direct 13C dimension. We propose these two sequences as a part of a suite of four N-C correlation experiments allowing for the assignment of protein backbone resonances in the solid state. We illustrate these experiments under ultra-fast magic angle spinning conditions on two samples of microcrystalline dimeric human superoxide dismutase (SOD, 153×2 amino acids), in its diamagnetic ("empty", Zn II) and paramagnetic (CuII, ZnII) states. MAS-tering sequences: Two pulse sequences aimed at the assignment of protein backbone resonances in the solid state under ultra-fast magic angle spinning (MAS) conditions are presented. Conceived for N-C correlation experiments, they consist of a combination of (1H,15N) and ( 15N,13C) selective cross-polarization steps with a J-based homonuclear transfer scheme, in which a spin-state-selective (S3E) block is incorporated to improve both resolution and sensitivity in the direct 13C dimension. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.