Fig. 5.

(A) ¹H‐NMR spectrum of ¹⁵N‐E5 expressed in fermenter. (B) The zoom of the ¹H‐NMR spectrum shows two different signal groups in the H(N) region: one is a typical resonance of backbone peptide H(N) (right) with a doublet with ¹J‐coupling of 93.0 Hz (assigned to Glu³), while the other belongs to the Trp indole side chain H(N) with a ¹J‐coupling of 99.0 Hz (left). (C) The zoom of the homonuclear ¹H,¹H NOESY spectrum proves that the three signals of Trp side chain and the two signals of the backbone belong to the same H(N) due to the same crosspeak pattern.