The Table  3 provides recommended carrier frequencies to be used in these experiments.

For 4D APSY-HACANH and 5D APSY-HACACONH the projection-dependent sweep widths were calculated from the default values in Table  3 with the use of Eq.  11 , whereas Eq.  9 was used for 5D APSY-CBCACONH, since the carrier frequencies of ω ₁ (C ^β ) and ω ₂ (C ^α ) have to be identical and the assumptions leading to Eq.  11 are thus not satisfied in this experiment.

Here, we describe the strategy followed for the selection of the APSY-NMR experiments to be used for sequence-specific polypeptide backbone resonance assignments in proteins (Tables  2 , 4 ).