Model

Aims

In our project, E.coli BL21 is engineered to produce spidroin by protein expression. As there’re many types of spidroin and each has its specific alternative properties, we can make silks with different properties and thus different usage of it, by controlling the production of spidroins. We aimed to achieve this target by proportional expression, while each recombinant plasmid contains independent inducible promoters. The gene expression thus the percentages of spidroins can be controlled by adjusting the concentrations of different inducers, IPTG and arabinose. To estimate the product amount, we use MATLAB Simbiology model builders and model analyzers to simulate the proportional expression. The relationship between product and inducer can be revealed by equations introduced and the concentration-time graph plotted. By developing models using Michaelis-Menten kinetics and mass actions kinetics, reactions between inducer and repressor can be shown and thus illustrated proportional gene expression. For simulations of both inducers, at t=0, 0.005M of inducers and a largely excess amount of DNA binded with the corresponding depressor are invested. The simulation was then run for 10 hours. The amounts of the inducers invested at the beginning were then changed to 0.004M, 0.003M…etc, and the simulations were performed again. By repeating the above steps, standard curves showing the relationship between inducers and protein concentration can then be obtained.