New pulse schemes for recording intermolecular NOEs in a molecular complex consisting of 15N,13C labeled and unlabeled components are presented. The pulse sequences select for magnetization transferred from protons on the unlabeled component to proximal protons of the labeled molecule. Filtering (suppression of signal from 13C labeled molecules) is accomplished using adiabatic 13C inversion pulses which are swept at a rate which is tuned according to the one-bond 1H−13C scalar coupling vs carbon chemical shift profile of the labeled molecule in the complex. Significantly improved spectra are obtained relative to data recorded with other purging schemes. Improvements are demonstrated in experiments where intermolecular NOEs between labeled RNA-unlabeled peptide and labeled protein−unlabeled peptide are recorded. A discussion of structural information obtained for a complex of the amino-terminal arginine rich domain of the N protein from bacteriophage λ and boxB RNA using the new methodology is presented.

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A new NMR experiment is described for recording NOEs from Val and Ile methyl groups in 15N,13C-labeled or methyl-protonated, 15N,13C,2H-labeled proteins that offers far superior resolution than conventional 3D 13C-edited NOESY data sets. Resolution is achieved by recording both the Cβ and Cγ (Val) or Cγ2 (Ile) chemical shifts as well as the chemical shift of the destination proton, and a strategy is introduced for refocusing homonuclear carbon couplings during the constant-time evolution of Cβ carbon magnetization. The utility of the method is demonstrated with applications on a 160-residue fully protonated 15N,13C-labeled, dNumb PTB domain−peptide complex and a methyl protonated, highly deuterated 15N,13C-labeled complex of maltose binding protein and β-cyclodextrin (42 kDa).