These dramatic spectral changes indicate that the binding of Zn 2+ induces conformational changes, demonstrating the high affinity of the apoprotein toward Zn, consistent with the ITC results described above. Also noteworthy is that many of the peaks in each protein form have similar chemical shifts, implying that the protein regions adopt similar tertiary structures. Specifically, we observed a downfield-shifted peak near 13.5 ppm in the ordered region and significant movement of multiple resonances (highlighted in circles, Fig. 6 ), suggesting that the involvement of the amide proton close to the Zn binding site.