Team:XMU-China/background
From 2012.igem.org
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Background and Approach Logic Gates
The AIM of our project is to construct a fluorescent digital display device of genetic circuits with synthetic logic gates. The finished device will display and switch numbers. Similar to electronic circuits, logic regulation operation in cells integrates the extracellular and intracellular signals. We assemble several pairs of promoters and their activators or repressors into computing building block of the circuit: PBAD-Arabinose, PcI-CI, and PtetR-TetR. These computation units act as genetic logic gates perform AND, OR and NOR gates function. Green Fluorescent Protein Cell Immobilization It is a technique to fix cells in a suitable matrix. Immobilized cells have been employed to perform biotransformation and reported to have higher production rates than freely suspended cells. In our project, we have selected three methods to immobilize our engineering bacteria:
Quorum Sensing Time Delay Constructing a unique display device which can let each unit light up one after another is beneficial for our team to accomplish the aim of time delay, which means that it is necessary to construct a series of cells those can express the characteristic of different time delay. As a result, we take advantage of Quorum-sensing system to change the time delay of GFP expression via different intensity of RBS. Original Design Brainstorm: Contents: Group 2: Bioscreen Project Overview Fortunately, 2012 XMU iGEM team has constructed a fluorescent digital display device with synthetic logic gates, which is able to respond to signals by displaying and switching numbers. We put GFP equipped with degradation tags in downstream to illuminate our numbers and change them quickly as well. Considering our engineering background, we accordingly employ cell immobilization to build our device. Engineering bacteria have been embedded in intra-hallow calcium alginate microcapsules and in PDMDAAC-NaCS microcapsules respectively. In addition, 3D CAD design is performed for a perfect device. Our genetic circuits vary in length and RBS strength, leading to different durations of time delay for GFP expression which inspired us to extend our work of 2011 XMU iGEM team. By altering the strength of RBS at five grades, another five circuits have been built.Once inducted by arabinose, the duration of response time for GFP expression increases as the strength of RBS declines, bringing about a time-course display. References [2] http://en.wikipedia.org/wiki/Green_fluorescent_protein [3]Eberhard A, Burlingame A. L, Eberhard C, Kenyon G. L, Nealson K. H, Oppenheimer N. J. Structural identification of autoinducer of Photobacterium fischeri luciferase[J]. Biochemistry, 1981, 20 (9): 2444–2449.
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