van't Hoff plot for the binding of VHHZnOBPtag (open circles), VHHZnOBP1 (closed circles), VHHsZnOBP3 (open squares), and 4F2 VHH (closed squares) to ZnO. Straight lines were obtained by fitting the four points to the linearized van't Hoff equation as follows: ln KD = ΔH/RT − ΔS/R, where ΔH is van't Hoff enthalpy; ΔS is van't Hoff entropy, and R is universal gas constant.