Figure 5.
Biosensor-based affinity determination of the ZIL-6_13 variant for IL-6. The affinity of affibody variant ZIL-6_13 to IL-6 was determined in a ProteOn biosensor instrument (BioRad). The affibody variant, expressed as an His6-Z fusion, was immobilized onto a sensorchip via primary amine coupling chemistry followed by injections of different concentrations (0.08, 0.40, 2.0, 10 and 50 nM) of IL-6 and the responses recorded (see Materials and Methods section for details). The experiment was performed in triplicate, using separate sensor chip surfaces. A representative set of response traces (background buffer effect subtracted) are shown in the figure. The affinity (KD) was in this experiment determined to 4.97 ± 0.3 × 10−10 M, i.e., ∼0.5 nM (500 pM).