Team:BIT/project biosensors

From 2013.igem.org

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      <td width="608" class="t1">Biosensors</td>
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      <td width="608" class="t1">Beta-lactam Detection Device</td>
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      <td class="t2">&nbsp;&nbsp;&nbsp;&nbsp;However, when tetracycline and IPTG are added, the TetR protein combines with the tetracycline. At the same time, the pTet promoter transcripts the the T7polymerase, which binds to the T7 promoter. Because IPTG has activated the LacI, the green fluorescence protein will be produced. Moreover, as the concentration of tetracycline is increasing, the intensity of the fluorescence will increase spontaneously. </td>
      <td class="t2">&nbsp;&nbsp;&nbsp;&nbsp;However, when tetracycline and IPTG are added, the TetR protein combines with the tetracycline. At the same time, the pTet promoter transcripts the the T7polymerase, which binds to the T7 promoter. Because IPTG has activated the LacI, the green fluorescence protein will be produced. Moreover, as the concentration of tetracycline is increasing, the intensity of the fluorescence will increase spontaneously. </td>
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      <td width="608" class="t1">Chromate Detection</td>
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      <td class="t2"><strong>Background</strong></td>
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      <td class="t2">&nbsp;&nbsp;&nbsp;&nbsp;Some illegal  dairies always add leather hydrolysate into fresh milk and powdered milk to  increase the percentage of protein in milk. Chromate, which is one of the  elements of leather dye, is the main element that can be used to trace leather  hydrolysate. Our Cr(VI)-biosensor is thus designed for the detection of  chromate in dairy products.<br>
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      &nbsp;&nbsp;&nbsp;&nbsp;Our Cr(VI)-biosensor is designed to work in  places where traditional biosensors cannot. This is important for consumers to  know that what they buy for their consumption is  qualified and safe to drink. While there are traditional  methods for detection of chromate(such as Graphite furnace atomic absorption  method, Oscillographic polarography, ICP-AES, High performance liquid  chromatography, Spectrophotometric investigation,etc.), all these methods have  to rely on laboratories equipped with precise,  expensive, experimental apparatuses. However, with  our Cr(VI)-biosensor,  even consumers  without specific training will be able to use it and the results will be knownin just a few hours.<br>
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      &nbsp;&nbsp;&nbsp;&nbsp;Cr(VI) is one of  the major environmental contaminants, which reflects its numerous high-volume  industrial applications and poor environmental practices in the disposal of  chromium-containing waste products. High solubility and tetrahedral  conformation of the chromate anion promote its rapid transport across  biological membranes, and once internalized by cells, Cr(VI) exhibits a variety  of toxic, mutagenic, and carcinogenic effects. Chromate and sulfate are  structurally similar anions, which makes it difficult for cells to  differentiate between them and is the basis for cellular uptake of chromate by  sulfate transporters. Formation of DNA damage is a major cause of toxic and  mutagenic responses in both human and bacterial cells, as evidenced by their  increased sensitivity to chromate in the absence of DNA repair. Human and other  mammalian cells lack detectable extrusion of chromate, and DNA repair is their  main cellular defense mechanism against chromate toxicity. Because bacterial  cells are less proficient in repair of chromium-DNA adducts compared to human  cells, their ability to survive in the environment with heavy chromate  contamination requires  selection of alternative resistance mechanisms.
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      <td class="t2"><strong>Design</strong></td>
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      <td class="t2">&nbsp;&nbsp;&nbsp;&nbsp;Genes conferring  resistance to chromate have been found in Pseudomonas spp., Streptococcus  lactis, Ochrobactrumtritici 5bvl1 and Cupriavidusmetallidurans. The  7,189-bp-long TnOtChr of Ochrobactrumtritici 5bvl1 contains a group of chrB, chrA, chrC, and chrF genes situated between divergently transcribed resolvase  and transposase genes.
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            <td class="t3"><img src="https://static.igem.org/mediawiki/2013/4/4f/BIT_CR_1.png" width="554" height="181">
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    <td class="t2">&nbsp;&nbsp;&nbsp;&nbsp;The chr promoter was strongly induced by chromate or dichromate, but it was completely unresponsive to Cr(III), oxidants, sulfate, or other oxyanions. Plasmid reporter experiments identified ChrB as a chromate-sensing regulator of chr expression. According to this evidence, we designed three kinds of devices working in E.coli (DH5α) to build Cr(VI)-biosensor.
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            <td class="t3"><img src=" https://static.igem.org/mediawiki/2013/6/6f/BIT_CR_2.png" width="493" height="350">
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    <td class="t2">&nbsp;&nbsp;&nbsp;&nbsp;The chr promoter has a weak constitutive expression without chromate, while it is strongly induced to express.<br>
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&nbsp;&nbsp;&nbsp;&nbsp;This device will work to detect the concentration of chromate in dairy products. At the same time, we designed another two devices to reduce the detection limit.
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            <td class="t3"><img src="  https://static.igem.org/mediawiki/2013/0/0d/BIT_CR_D1.png" width="555" height="307">
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    <td class="t4">Device 1
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            <td class="t3"><img src="  https://static.igem.org/mediawiki/2013/f/ff/BIT_CR_D2.png" width="466" height="472">
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    <td class="t4">Device 2
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