The dissociation constant was calculated using k-ELISA, according to the procedure firstly described by Friguet . Phages (~10 10 pfu/ml corresponding to about 16 pM) were preincubated with different concentrations of TnT from 0 to 4 ng/ml (which corresponds to 108 pM). Next, mixtures were transferred into wells precoated with 0,25 μg/ml of TnT (or BSA). Further steps were performed in the same manner as for phage concentration measuring experiments.