Measurement of the continuous distribution of binding sites in molecularly imprinted polymers

Reported is the first affinity spectrum (AS) [number of binding sites (N) vs. association constant (K)] for a non-covalently imprinted polymer. The AS method yields the distribution of sites over a continuous range of binding constants and characterizes the heterogeneity present in imprinted polymers better than current methodologies. To demonstrate the generality of the AS method, the distributions for three different imprinted polymers (two of which were taken from the literature) were calculated from their respective binding isotherms. The shapes of the distribution curves were different yet consistent with the respective covalent or non-covalent imprinting mechanisms. Finally, the binding parameters derived from the AS method were compared with those determined by the more common Scatchard analysis and were in general agreement.