Figure 4.

Comparison of fitting models for KWK₆ binding to dT(pdT) ₂₂ at 0.105 M Na⁺ with Z_L = 8, |Z_D| = 22, and Q_max = 0.95. Symbols are as defined in Figure 1. The dashed line represents the global fit to the Epstein model (Equation 2) with logK_obs = 5.605 ± 0.01. The solid line is the improved global fit to an Epstein model where two ligands can bind (Equation 12) with different affinities K_obs,1 and K_obs,2: logK_obs,1 = 5.734 ± 0.01 and logK_obs,2 = 5.434 ± 0.02. The F_χ-value (38), which tests the statistical significance of an increase in the number of fitting parameters, confirms that the use of two different binding constants describes KWK₆-dT(dT)₂₂ binding better (at a 95% confidence level) than the Epstein model with only one binding constant.