*4.2. Nuclear Magnetic Resonance Spectroscopy*

Purified peptides were dissolved in H2O/D2O (9:1 ratio by volume) in the presence of 50 mM sodium deuterioacetate buffer (pH 5.5 uncorrected). Peptide concentrations were 2.0–15.4 mM. 2-Dimethyl-2-silapentane-5-sulfonate (DSS) was added to the sample as an internal reference. All NMR experiments were performed on a Brüker AVIII 800 MHz spectrometer (Bruker, Billerica, MA, USA). <sup>1</sup>H-1H homonuclear phase-sensitive doublequantum filtered-correlated spectroscopy (DQF-COSY) [33], total correlation spectroscopy (TOCSY) [34], and rotating-frame nuclear Overhauser effect spectroscopy (ROESY) [35] experiments were performed by collecting 2048 point in f<sup>2</sup> with 4–8 scans and 256–512 points in f<sup>1</sup> at 298 K. Solvent suppression was achieved by the WATERGATE solvent suppression sequence [51]. TOCSY and ROESY experiments employed a spin locking field of 10 kHz. Mixing times of 60 and 200 ms were used for the TOCSY and ROESY experiment, respectively.
