Figure 4.
XWKK binding isotherms as a function of pH. Titrations of (A) KWKK at 24.4 mM Na+ or (B) HWKK at 9.8 mM Na+ as a function of polyU. Data from titrations peformed at 25 °C with 4 μM oligopeptide are presented for each pH with the following symbols: (●), pH 5.2; (○), pH 6.0; (■), pH 7.0; (□), pH 8.0; (◆), pH 8.7. Curves represent fits determined by global nonlinear least squares analysis across all oligopeptide concentrations (2 – 6 μM) at the specified pH and salt concentration (cf. Figure 3). Lines represent the best global fits to the data when the site size is constrained to n = 4 (dashed lines) or n = 5 (solid lines; Table 1).
