Refractive index, interactions between surfaces

Figure 11.4 Illustration of the SPR experiment. The binding of BACE to the immobilized small peptidic reference compound is detected by a change in refractive index at the chip surface. Preincubation of BACE with a test compound blocks the interaction with the immobilized reference compound in a manner that is dependent on the concentration of the test compound and its affinity for BACE. In practice, we could rank affinities by comparison of the SPR response at a fixed concentration of the test compound and then quantitatively determine the affinity by analyzing the concentration response dependence. In this example, the inhibitor in the middle panel (Inhibitor 1) has weaker affinity than the inhibitor in the lower panel (Inhibitor 2) because, at equivalent concentrations, Inhibitor 2 more extensively blocks the interaction between BACE and the immobilized peptidic inhibitor.

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