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Different two-dimensional NMR schemes for generating ¹H-detected ¹H¹⁵N and ¹H¹³C correlation spectra are compared. It is shown that the resolution in the dimension that represents the ¹³C or ¹⁵N chemical shift depends on the type of correlation scheme used. For ¹⁵N NMR studies of proteins, it is found that experiments that involve ¹⁵N single-quantum coherence offer improved resolution compared to multiple-quantum correlation experiments, mainly because the ¹H¹H dipolar broadening of the multiple-quantum coherence is stronger than the heteronuclear dipolar broadening of ¹⁵N, but also because of the presence of unresolved J splittings in the F₁ dimension of the multiple-quantum correlation spectra. For ¹³C, the heteronuclear dipolar interaction is much larger and the ¹H¹³C multiple-quantum relaxation is slower than the ¹³C transverse relaxation; however, because of the presence of ¹H¹ …