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A biosynthetic strategy has recently been developed for the production of 15N, 13C, 2H-labeled proteins using 1H3C-pyruvate as the sole carbon source and D2O as the solvent. The methyl groups of Ala, Val, Leu and Ile (?2 only) remain highly protonated, while the remaining positions in the molecule are largely deuterated. An (H)C(CO)NH-TOCSY experiment is presented for the sequential assignment of the protonated methyl groups. A high-sensitivity spectrum is recorded on a 15N, 13C, 2H, 1H3C-labeled SH2 domain at 3°C (correlation time 18.8 ns), demonstrating the utility of the method for proteins in the 30–40 kDa molecular weight range.

Summary 113Cd-1H NMR correlation experiments have been extremely useful for determining the amino acid ligands that form metal-binding sites in proteins. To date, the majority of these methods have used heteronuclear multiple-quantum transfer as the basis for establishing correlations. In this paper, we demonstrate the feasibility of using correlation methods that employ heteronuclear cross-polarization (hetero TOCSY) as viable alternatives. Additionally, we couple hetero TOCSY with selective excitation and transfer procedures to take advantage of the small number of heteronuclei usually present in metalloprotein systems. One- and two-dimensional experiments are presented as examples of these techniques.