Figure 2.

Biophysical characterization of the Z_SPA-1 affibody. (a) Section of the ¹H-¹⁵N heteronuclear single quantum correlation spectrum of ¹⁵N-labeled Z_SPA-1 in the absence (red) and presence (blue) of the unlabeled Z domain. (b) CD at 20°C of Z and Z_SPA-1 at 25 μM concentrations, and of Z_SPA-1 at higher concentrations (as indicated) in 20 mM potassium phosphate (pH 5.6). (c) Fluorescence emission spectra of 50 μM ANS in buffer and in the presence of equimolar amounts of Z, Z_SPA-1, and the Z:Z_SPA-1 complex. All solutions contained 20 mM potassium phosphate (pH 5.6), and ANS was excited at 396 nm. (d) Thermal melting of Z and Z_SPA-1 at 25 μM monitored by CD at 208 nm.