Figure 4.

(a) Far-UV CD spectra of chemically synthesized proteins (csRBD/H, cs[L91D,L-O]RBD/H) and RBD proteins expressed in E. coli (RBD/H, [L91W]RBD/H). Spectra were obtained at 20°C in 20 mM phosphate, pH 7.4 with a protein concentration of 95 μM. (b) Fluorescence spectra of cs[L91L-O]RBD/H and biosynthetic [L91W]RBD/H were measured at 25°C in 100 mM NaCl, 50 mM Tris⋅HCl, 5 mM MgCl₂, pH 7.4 with a protein concentration of 2 μM. The excitation wavelength was 290 nm.