Record long-distance relationships in solid-state protein NMR

A novel pulse sequence has extended the length of ¹³C-¹³C interactions in proteins in solid-state NMR spectroscopy up to 9.6Å, the longest probed in proteins to date. Scientists in China, Japan and France worked together to devise the recoupling seqeunce they called SHA+, which is based on the SHANGHAI (Second-order Hamiltonian among analogous nuclei generated by hetero-nuclear assistance irradiation) method. As they describe in ChemPhysChem, broadband ¹³C spin diffusion is assisted by ¹H irradiation to give efficient ¹³C-¹³C correlation at high magnetic fields and high magic angle spinning (MAS) frequencies.

The new procedure was demonstrated using the Aβ42 amyloid fibril in which the phenylalanine-20 residue was uniformly labelled with ¹³C and ¹⁵N and the adjacent alanine-21 residue was selectively labelled at C^β with ¹³C. It allowed polarisation transfer between ¹³C atoms that were 7.8-9.6Å apart, the most distant ¹³C-¹³C correlation reported to date in solid-state NMR spectroscopy of proteins.