Selectivity and sensitivity improvement in co-operative systems with a threshold in the presence of noise

High selectivity (specificity) and sensitivity to natural or artificial stimuli which are normally observed for biological systems can be realized in an ensemble composed of many co-operatively connected primary receptors. The co-operative interaction results in the formation of several stable states and a switching from one state to another is performed in a threshold manner. When any noise is absent the ensemble with a threshold can secure as high a selectivity and sensitivity as is desired. The presence of noise sets limits on the possible informational quality of a system because spontaneous switchings will occur. The question: What advantage as regards selectivity and sensitivity can a co-operative system with a threshold have is considered quantitatively as an example for a bistable chemical system. As a result it is established that a co-operative system may have much higher selectivity and sensitivity than its individual primary receptors.