f1 / ppm S30-31); regions of continuous up-field (i.e. negative) shifts indicate helicity. In agreement with Cα secondary shifts, a continuous series of up-field Δẟ α secondary shifts were observed between Glu73 N-Myc and Gly89 N-Myc for the linear control peptide at 5 °C, of relatively small magnitude (Δẟ α ~ 0.2), indicating weak helix propensity. The calculated Δẟ α values profiled also two structural regions, one at the N-terminus of the peptide displaying higher Δẟ α values around Val78 N-Myc , and a second towards the C-terminus, where consistently lower Δẟ α are observed. For the constrained peptide at 25 °C we found a similar general trend, with Δẟ α values in the same range but slightly lower in magnitude.