In our work, analysis was performed for clones: A3, B7, D11 and wild-type M13. These clones were selected for further analysis because they exhibited the highest affinity in screening and could be easily amplified; therefore, the C9 clone was not chosen. The phages' total concentration was about 1x10 10 pfu/ml (16 pM) and was carefully determined using the biological method immediately before analysis. The range of ratios of total TnT and total phage concentration was 1:2, 1:1, 2:1 and 4:1. Increasing TnT concentration causes an increase in the saturation of phage-displayed receptors. As a result, a decrease in the ability to bind to immobilised TnT molecules occurs. Experimental data from the experiments were analysed according to the presented mathematical model. Calculated values of Kd (from linear slope regression) are listed in Table .