Team:PKU Beijing/Project/Bistable Design

Abstract

Bi-stable part is one of the core achievements of PKU07 iGEM team. We inherited the part and utilized it to function as a memorizer in our own system. This bi-stable module can be stabilized as either of the two states in a relatively long period of time without any external stimuli, while under certain circumstances, one state can be turned over to the other. These two properties meet the requirements as a memorizer in our system. The two states can be utilized as two states of a memory, and the alteration from one state to the other functions as the process of a memory foundation. Moreover, the natural switchover from one state to the other can accurately mimic the oblivion phenomenon.

The logic design and construction of bi-stable module

The bi-stable part is composed of CI and CI434 which repressed each other in transcription. As is seen in the logic picture, both of the two coding genes are constructed after the promoter which is repressed by the other, and CI can also play the role of an activator of its own promoter. GFP and mRFP are separately constructed after CI and CI434 coding gene as reporters of the different states. In state 1, when CI is expressed, the promoter before CI434 is repressed, leading to the downregulation of CI434. Thus the repression of the promoter before CI is removed, positively upregulates the expression of CI. As is the same of state1, in state 2, when CI434 is highly expressed, the expression of CI is repressed and the state can be stabilized in CI434 high level of expression.

fig2. Bistable part

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