Probing Supramolecular Structure from Measurement of Methyl ¹H−¹³C Residual Dipolar Couplings

A simple NMR experiment is presented for the measurement of methyl ¹H−¹³C residual dipolar couplings in fractionally aligned supramolecular protein complexes. The approach makes use of methyl-TROSY spectroscopy that significantly increases the lifetime of the NMR signal, along with highly deuterated, methyl-protonated samples that minimize relaxation contributions from protons external to the methyl group probes. An application to a 360 kDa half-proteasome complex is presented, establishing the methodology.