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| | <b>Cutinase Activity</b><br> | | <b>Cutinase Activity</b><br> |
| - | Through our p-nitrophenyl butyrate (pNPB) assays we have gathered enough data to determine that our LC-Cutinase part (<a href="http://partsregistry.org/wiki/index.php?title=Part:BBa_K936000">BBa_K936000</a>) exhibits its intended function as an esterase. The results below were acquired through assays conducted with cell culture samples. We decided to use cell cultures in these runs because in actual application we would like to incubate cells directly with PET and because given the results of our last experiments, we are confident that pelB is working to secrete the enzyme. A more detailed description of these assays can be found on the Module Engineering Project page. | + | Through our p-nitrophenyl butyrate (pNPB) assays we have gathered enough data to determine that our LC-Cutinase part (<a href="http://partsregistry.org/wiki/index.php?title=Part:BBa_K936000">BBa_K936000</a>) exhibits its intended function as an esterase. The results below were acquired through assays conducted with cell culture samples. We used cell cultures in these runs because in actual application we would like to incubate cells directly with PET and because given the results of our last experiments, we are confident that pelB is working to secrete the enzyme. A more detailed description of these assays can be found on the Module Engineering Project page. |
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| | The first of these runs was conducted with cutinase regulated by both a constitutive promoter (BBa_J23101) and the inducible pBad promoter (BBa_K206000) in the MG1655 strain of <i>E. coli</i>. We included a negative control of BBa_J04450 in MG1655 and another negative control of the pNPB buffer with LB instead of cells to get an idea of any background esterase activity. The figure below displays the absorbance at 405 nm of each sample after 8 hours with the OD of the pNPB buffer control subtracted. The catalytic activity of cells expressing LC-Cutinase is clearly higher than that of the background. | | The first of these runs was conducted with cutinase regulated by both a constitutive promoter (BBa_J23101) and the inducible pBad promoter (BBa_K206000) in the MG1655 strain of <i>E. coli</i>. We included a negative control of BBa_J04450 in MG1655 and another negative control of the pNPB buffer with LB instead of cells to get an idea of any background esterase activity. The figure below displays the absorbance at 405 nm of each sample after 8 hours with the OD of the pNPB buffer control subtracted. The catalytic activity of cells expressing LC-Cutinase is clearly higher than that of the background. |
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| - | We attempted to redo the previous run while measuring OD 600 as to find the OD 405 per cell of each sample. Below are the results for enzyme activity of cutinase expressed by a constitutive promoter (BBa_J23101), the inducible pBad promoter (BBa_K206000), and a negative control (BBa_J04450 in pSB1A2). The plot on the right includes the results for the pBad expressed cutinase mutants described in the Protein Engineering section. | + | We attempted to redo the previous run while measuring OD 600 as to find the OD 405 per cell of each sample. Below are the results for enzyme activity of cutinase expressed by a constitutive promoter (BBa_J23101) and a negative control (BBa_J04450 in pSB1A2). |
| - | These results show that some of the mutants may have higher activity but do not confirm the findings of the previous run suggesting that cutinase has a higher esterase activity than the negative control. | + | These results show that cutinase has higher catalytic activity than that of the background, but not by the same relative amount as we saw in the previous run. |
| | + | <br><center><img src="https://static.igem.org/mediawiki/2012/6/63/UCDavisParts4.png"></center> |
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| - | <a href="https://static.igem.org/mediawiki/2012/e/e2/UCD_Data_large_13.jpg" class="lightbox"><img src="https://static.igem.org/mediawiki/2012/0/0e/UCD_Data_13-1.jpg " align="left"> </a>
| + | When repeating this run a third time, we see a similar trend. Cutinase activity is higher than the background, but at a different relative amount. |
| - | | + | <br><center><img src="https://static.igem.org/mediawiki/2012/2/28/UCDavisParts5.png"></center> |
| - | <a href="https://static.igem.org/mediawiki/2012/b/bb/UCD_Data_large_14.jpg" class="lightbox"><img src="
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| - | https://static.igem.org/mediawiki/2012/c/cb/UCD_Data_14.jpg " align="right"> </a>
| + | These results confirm that LC-Cutinase does demonstrate esterase activity but again suggest that the expression is variable and that further characterization is needed. |
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| - | <br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>We ran the assay once again with only constitutively expressed cutinase (with BBa_J23101) and the negative control (BBa_J04450 in pSB1A2). This time, the results reasserted the initial finding that the expressed cutinase had a higher activity than the control.
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| - | <a href="https://static.igem.org/mediawiki/2012/f/f3/UCD_Data_large_15.jpg" class="lightbox"><img src="https://static.igem.org/mediawiki/2012/ c/ c8/ UCD_Data_15. jpg" ></a></center> | + | |
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| - | From the first and last results, we can conclude that the LC-cutinase catalyst most likely behaves as expected. That is to say that it behaves as an esterase and breaks down the pNPB in the assay at a distinguishable rate. However, the middle results show inconsistencies that suggest that we should conduct more runs in the future. We are currently working to purify the cutinase enzyme which will allow us to redo these runs with a standardized enzyme concentration. This will allow for more repeatable and reliable results.
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