Team:NTNU-Trondheim/Model

As the levels of inducer increases, the steady state of the protein product increases up until it reaches 1200 molcules. An huge increase in inducer over 10 000 molecules will not give a RFP steady state of over 1200. The steady state is determined by the rates K4, K5, D1 and D2. During the model building and working with analysis of the model (both deterministic and stochastic), we noticed that the system would easily enter saturation: The levels of the inducer were irrelevant to the steady state levels of the RFP. Only when the following conditions are met: K1 « K11 and K2 « K22, we will find a tunable response of the system with varying inducer levels. When these requirements are not met, the system will not dependent on the level of inducer as the system early will be saturated. The reason for this is that there is a limited number of sites in the available DNA for binding with the active inducer, so that elongation and translation can take place. When these sites are fully occupied, further increases of inducer levels will have no effect. While the Xyls system typically is in a high-copy plasmid, the number (~30-50) of binding sites is a very small number compared to the concentrations of inducer and xyls molecules.