Fig. 2.

Set of two planes from the 3D (H)NHH and (H)N(HH)NH spectra. Strips taken at the ¹⁵N chemical shifts of Y75 (left) and L87 (right) from the (H)N(HH)NH and (H)NHH spectra, respectively. The proton–proton cross-peak pattern is indicative of cross-strand hydrogen bonding between the backbone amide and carbonyl groups of tyrosine 75 and leucine 87. Red lines correspond to the ¹H and ¹⁵N chemical shifts of L87. Blue lines correspond to the ¹H and ¹⁵N chemical shifts of Y75. A total of four cross peaks are present at the intersections of red and blue lines. Dotted circles indicate positions of potential sequential cross peaks (see text)