Fig. 3.

¹³C–¹³C side-chain correlation spectra of a large protein. a Isoleucine ¹³C^δ1–¹³C^γ1 and c valine ¹³C^γ–¹³C^β correlation spectra of a 0.5 mM sample of the 82-kDa protein MSG. Each of the two spectra in a and c were recorded in 7.5 h at 18.8 T using a standard helium-cooled Bruker TCI radio-frequency probe. b Correlating the ¹³C^δ1–¹³C^γ1 of isoleucine with the rest of the side chain ¹³C for chemical shift assignment. Representative TOCSY strips from a three-dimensional ¹³C-detected CC-TOCSY experiment (see Supplementary Fig. 8) for I229 and I309 (marked with black arrows in a. Chemical shift assignments in a and c were obtained from (refs. ^26,27) combined with the 3D-CC-TOCSY. Peaks labelled Ile in c are isoleucine ¹³C^γ2–¹³C^β correlations. All experimental parameters are given in Supplementary Materials and Methods