Open Access Kent State (OAKS)

We investigate the effects of a heterogeneous distribution of affinity constants on association/dissociation and displacement reactions. Through a theoretical analysis, we show that the low-concentration limit of the reaction isotherm depends exclusively on the high-affinity tail of the distribution. If the high-affinity tail decays rapidly, the reaction follows the standard Langmuir isotherm. However, if the high-affinity tail decays slowly, the form of the isotherm crosses over to the Sips isotherm. The threshold for this crossover is different for association/dissociation and displacement reactions. These results have broad implications for the assessment of heterogeneity in displacement assays.