|In the second project phase, we carry out label-free competition experiments. The dually labeled complex is titrated with a dilution series of the unlabeled compound(s) of interest and the decrease of cross correlating complex particles plotted against the concentration of this compound. From the resulting decay curve, the IC50 value can be deduced. Using the Cheng-Prusoff equation, affinity values (KI) of the unlabeld compound to the target are determined. Within this project phase, the kinetics of binding of the unlabeled compounds to the target are also determined (see kinetics of non-labeled interactors).