According to the first approach, the ELISA signal is linearly proportional to the concentration of phages exposing at least one active site or linearly proportional to the logarithm of the concentration of these forms (Supplementary Materials, Eq. S23 and S25, respectively). The signal tends to be proportional to the logarithm of concentration in a wide range of concentrations and linear in a specified narrow range. On the other hand, the signal may be proportional to the total concentration of active sites, i.e., to the concentration of each TnT-