¹¹³Cd-¹H hetero TOCSY: A method for determining metal-protein connectivities

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.