An efficient strategy for assignment of cross-peaks in 3D heteronuclear NOESY experiments

The question is addressed of how maximal structural NOE data on double labe lled proteins can be acquired with a minimal set of NOESY experiments. Two 3D-NOESY spectra are reported which, in concert with other commonly used sp ectra, provide a convenient strategy for NOE assignment. The 3D CNH-NOESY a nd 3D NCH-NOESY provide NOE connectivities between amide protons and carbon -bound protons and constitute orthogonal heteronuclear filters which elimin ate diagonal signals, considerably improving spectral quality. Two differen t heteronuclear chemical shift dimensions are recorded in the spectra, thus exploiting the extra dispersion of the heteronucleus and considerably simp lifying assignment.