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From 2013.igem.org

How They Work: Sucrose is a disaccharide composed of glucose and fructose. The sucrose is converted to lactic acid by S.Mutans which leads to plaque formation and tooth decay. We used operon repressors for both sucrose and fructose to detect the concentrations of both of them. By using the repressor systems, we can detect the formation of plaque and prevent the formation of cavities. We have chosen two repressors for use in this project: FruR, CscR. The FruR gene encodes a protein which normally binds to and represses the fructose operon. When fructose is present in the system, it binds to the FruR protein and prevents it from repressing the operon promoter. CscR works in the similar way, but it will bind to sucrose.

What We Did: We isolated and tested these repressors, FruR and CscR, and their corresponding operons.

<img src="http://i826.photobucket.com/albums/zz188/lana_khazma/fancy%20stuff/sucrstuff_zps30aefeaf.png" border="0" alt=" photo sucrstuff_zps30aefeaf.png" width=380 />

<img src="http://i826.photobucket.com/albums/zz188/lana_khazma/fancy%20stuff/fruRstuff_zpsaf5e8f5b.png" border="0" alt=" photo fruRstuff_zpsaf5e8f5b.png" width=410 />