Fig. 2.

(3,2)D (HACA)NCOCX: subspectra comprising signals located at sums (a) and differences (b) of ¹⁵N and ¹³C′ chemcial shifts along F1 are shown on the left and right, respectively, of the central peak spectrum comprising signals at ¹⁵N chemical shifts. Positive contours above 6 times the RMS noise floor are drawn for each spectrum with contour separation factor of 1.3. The total measurement time was 87 min (t₁ 96 × 180 μs; t₁′ 96 × 90 μs). As an illustration, selected peaks are labeled and connected. Labels correspond to the destination peak with the source atom consisting of the succeeding residue’s amide ¹⁵N and a ¹³CO component as appropriate. Dashed horizontal lines were added to connect peaks from the same residue