113Cd NMR spectra of controls, octarepeat (OR) segment, full-length PrPC, and relevant mutants. (left) 113Cd NMR spectra with chemical shifts referenced to 0.1 M Cd(ClO4)2 (aq). Spectra for the OR peptide (4-Octa peptide) and all proteins were acquired with 300 μM peptide/protein and 1.0 mM 113Cd2+. The vertical line is drawn as a reference against wild-type protein. (right) A stick diagram of the 113Cd NMR spectra ordered by chemical shift from high to low (with reference CdCl2 at the top). As noted at the top, nitrogen coordination decreases chemical shielding, leading to higher chemical shift values, whereas oxygen coordination shifts in the opposite direction.