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Results
Raw results

Results



To analyze our Clickable Outer Membrane Proteins, we have carried out many experiments. Our experimental approach towards these COMBs has been described in our Experimental Approach. For a more in-depth review of our results, take a look at our raw data page. Here, we hope to shortly present our achievements with our COMB Prototypes.


COMB Prototype I: The mNeonGreen & NanoLuc BRET Pair



To analyze the performance of the mNeonGreen & NanoLuc containing COMBs, we cloned both membrane proteins separately in the pETDuet-1 vector as well as both in a single vector. For both the vector containing either NanoLuc or mNeonGreen and the vector containing both proteins, we analyzed whether the click reaction occured and whether bioluminescence and fluorescence could be measured. An overview of our achievements is shown below.

OmpX-mNeonGreen

  • Verification of the click reaction and whether the protein is located in the outer membrane
    The click reaction should be specific and therefore should only take place on the unnatural amino acid (pAzf). The click reaction for OmpX-mNeonGreen was tested using DBCO-PEG4-TAMRA, a fluorescent dye functionalized with DBCO.
    As can be seen in the figure below, the bacteria which had pAzF available (green) showed higher fluorescence intensity than the negative controls (purple and blue).
    This indicates that the click reaction occurs.

  • Verification of fluorescence
    The fluorescent protein mNeongreen should be intact, this is tested by laser excitation. The emission spectrum, as can be seen below, shows a peak at a wavelength of 517 nm. Whereas the negative control, OmpX-SmBit & OmpX-Lgbit, do not show any peaks at all. Indicating that mNeongreen is indeed present and intact in the cell.

OmpX-NanoLuc

  • Verification of the click reaction and whether the protein is located in the outer membrane
    The click reaction should be specific and therefore should only take place on the unnatural amino acid (pAzf). The click reaction for OmpX-NanoLuc was tested using DBCO-PEG4-TAMRA, a fluorescent dye functionalized with DBCO.
    As can be seen in the figure below, the bacteria which had pAzF available (green) showed higher fluorescence intensity than the negative controls (purple and blue).
    This indicates that the click reaction occurs.

  • Verification of bioluminescence
    The presence of the luciferase, OmpX-NanoLuc, in the cells is tested by adding its substrate (Nano-Glo). Bioluminiscence is measured using a spectrophotometer, the spectrum is shown in the figure below. After addition of the Nano-Glo substrate (which contains furimazine) OmpX-NanoLuc shows a peak characteristic for NanoLuc, indicating NanoLuc's presence within the cells.


OmpX-mNeonGreen & OmpX-NanoLuc

  • Verification of the click reaction & localization in the outer membrane
    The click reaction should be specific and therefore should only take place on the unnatural amino acid (pAzf). The click reaction for OmpX-mNeonGreen & OmpX-NanoLuc was tested using DBCO-PEG4-TAMRA, a fluorescent dye functionalized with DBCO.
    As can be seen in the figure below, the bacteria which had pAzF available (green) showed higher fluorescence intensity than the negative controls (purple and blue).
    This indicates that the click reaction occurs.
  • Verification of fluorescence
    OmpX-mNeonGreen's presence in the cells was verified by measuring mNeonGreen's presence in the platereader. The peak with its maximum at 517 nm indicates that mNeonGreen is indeed present. Cells without mNeonGreen showed no response in fluorescence measurement, indicating that the peak originates from OmpX-mNeonGreen.
  • Verification of bioluminescence & BRET
    OmpX-NanoLuc's & OmpX-mNeonGreen's presence in the cells were tested by adding Nano-Glo substrate to the cells and measuring bioluminescence with the spectrophotometer. The figure below shows that OmpX-NanoLuc shows a peak characteristic for NanoLuc, indicating NanoLuc's presence within the cells. Moreover, the spectrogram shows a distinct shoulder near 517 nm, the emission wavelength of mNeongreen. Since no laser was used, excitation of mNeongreen can only be accomplished by NanoLuc so BRET occured. This signal is measured when no click reaction is performed on the complex, meaning that this can be seen as the background noise of the sensor.






COMB Prototype II: NanoBiT



For NanoBiT, we undertook the same approach as for our BRET pair: we cloned the parts together into a single pETDuet-1 vector as well as separately into different vectors. For all of these constructs, we determined whether the click reaction occured, and if bioluminescence and fluorescence was visible.

OmpX-LgBiT

  • Verification of the click reaction and whether the protein is located in the outer membrane
    The click reaction should be specific and therefore should only take place on the unnatural amino acid (pAzf). The click reaction for OmpX-LgBit was tested using DBCO-PEG4-TAMRA, a fluorescent dye functionalized with DBCO.
    As can be seen in the figure below, the bacteria which had pAzF available (green) showed higher fluorescence intensity than the negative controls (purple and blue).
    This indicates that the click reaction occurs.

OmpX-SmBiT

  • Verification of the click reaction and whether the protein is located in the outer membrane
    The click reaction should be specific and therefore should only take place on the unnatural amino acid (pAzf). The click reaction for OmpX-SmBit was tested using DBCO-PEG4-TAMRA, a fluorescent dye functionalized with DBCO.
    As can be seen in the figure below, the bacteria which had pAzF available (green) showed higher fluorescence intensity than the negative controls (purple and blue).
    This indicates that the click reaction occurs.

NanoBiT

  • Verification of the click reaction & localization in the outer membrane
    The click reaction should be specific and therefore should only take place on the unnatural amino acid (pAzf). The click reaction for OmpX-LgBit & OmpX-SmBit was tested using DBCO-PEG4-TAMRA, a fluorescent dye functionalized with DBCO.
    As can be seen in the figure below, the bacteria which had pAzF available (green) showed higher fluorescence intensity than the negative controls (purple and blue).
    This indicates that the click reaction occurs.
  • Verification of bioluminescence
    When both OmpX-SmBiT & OmpX-LgBiT are present in the cell they can come together and form a complex. In both domains form a complex (NanoBit) bioluminiscence can be measured. For future sensor use this can be seen as background noise. The combination of OmpX-SmBiT and OmpX-LgBiT showed a bright peak, whereas cells expressing either OmpX-SmBiT or OmpX-LgBiT showed no such peak, indicating that the split luciferase is present in the cells and works.




Tests with our COMB Prototypes


After having verified the sequence and structural integrity of both our COMBs, we could start testing our device. An overview of the tests we have carried out is shown below:

Verification of the DNA-click


The first step taken after obtaining working COMBs was to verify whether the DBCO click occured with DBCO-functionalized DNA. To verify this, DNA was clicked to the outer membrane proteins in the same ratio as with the TAMRA test. After having clicked complementary DNA to the COMBs, the presence of complementary DNA could be verified through the addition of a complementary, fluorescent DNA strands. To verify whether both complementary strands clicked to the COMBs, the COMBs with clicked DNA strands were incubated simultaneously with two different fluorescent complementary strands. The first oligo was Cy5-labeled, the second was TAMRA-labeled (see the Figure below). Fluorescence of the individual cells was subsequently measured using the FACS.
Dimerization of DNA-fluorophores to clicked DNA
After verifying the click of DBCO-Tamra to all of our constructs the next step can be made. This time DBCO-DNA is clicked, subsequently two types of DNA-fluorophores are added to anneal. One fluorophore, Cy5, is deplicted in the figure below on the axis called "Alexa 633A" (which is its filter) showing its intensity. The other fluorophore, Tamra, is deplicted in the figure below on the axis called "PE-A" (which is its filter) showing its intensity. As one can see in figure A there is a strong correlation between bacteria (dots) both having a high intensity Cy5 and Tamra fluorescence. Figure B represents the negative control where the DBCO-DNA is not added, so no clicked occured.

Ga typen Hans