Fig. 2.

Effect of Cu-cyclam on tryptophan indole NH resonances of lysozyme. (Lower) The low-field region of the ¹H NMR spectrum of HEWL in 90% H₂O/10% D₂O before and after addition of 10 mol equiv of the Cu-cyclam complex 1. The pH of the solution (4.6) was chosen so as to be close to that under which lysozyme readily crystallizes. As is evident from the plot of linewidth versus Cu-cyclam concentration (Upper), there are specific paramagnetic broadening effects on Trp-62, Trp-63, and Trp-123, implying that these residues are close to the bound Cu²⁺. The linewidth of the backbone NH resonance of Cys-76 is also shown for comparison.