Peptide NMR analysis and secondary chemical shift calculation: NMR studies were recorded on a Bruker AV4 NEO 11.75 T (500 MHz 1 H) NMR spectrometer (500-4C) at either 278 or 298 K, using water suppression by means of excitation sculpting with gradients using perfect echo. All samples were prepared in a buffer/D2O mixture (90/10 vol/vol) to achieve a final concentration of 3 mM (buffer: 25 mM potassium phosphate, 50 mM NaCl, 5 mM MgCl2, pH= 7.5). For each sample a complete set of experiments was performed, where 1 H-NMR, 1 H-1 H TOCSY (20 and 80 ms) and 1 H-1 H COSY were employed to assign the identity of each amino acid present in the peptide sequence, and 1 H-1 H NOESY was employed to establish the inter-residue connectivity and spatial correlations. Folded and unfolded 1 H-13C{ 1 H} HSQC spectra were used in all cases to characterize the C nuclei and to support full 1 H assignment.