FIGURE 1.

Comparison of the amide backbone chemical shifts in the oxidized and reduced (DTT) form of A452C/S652C mutant of GluA2 LBD bound to glutamate (A; Protein Data Bank code 3T93), iodowillardiine (B; Protein Data Bank code 3T96), and kainate (C; Protein Data Bank code 3T9H). On the right is shown the ¹H,¹⁵N-HSQC spectrum, and on the left, a representation of the resonances that have shifted upon reduction of the A452C/S652C disulfide bond is shown. The oxidized form is identical with no additions and in the presence of Cu-phenanthroline, suggesting that the disulfide bond forms spontaneously. The difference in chemical shift between the oxidized and reduced from was quantitated using the formula, chemical shift difference = $\sqrt{{\left(\left({\Delta }^{15}\text{N}\right)/8\right)}^2+{\left({\Delta }^1\text{H}\right)}^2}$. Residues were assigned colors with a chemical shift difference between 0 and 5 assigned to a rainbow of colors from blue to red.