Photoactivated Localization Microscopy with Bimolecular Fluorescence Complementation (BiFC-PALM)

The overall goal of this microscopy technique is to visualize protein, protein interactions at the single molecule and nanometer scale. So this method can help us to answer some key questions in the field of biology, such as molecular interactions in oncogenic signaling processes. The main advantage of this technique is that it's sensitive, specific and it offers single molecule and nanometer resolutions.

Demonstrating the procedure will be Dr.Tahan, a senior research associated in my laboratory After cloning RAs and RAF R-B-D-P-A-M Cherry one fragments packaging into viral particles and infecting U2 OS cells according to the text protocol. To prepare a sample for imaging plate about 5.5 times 10 to the fourth stable expression cells per well of an eight well glass bottom chamber Slide in 350 microliters of phenol red free DMEM. Use fresh paraldehyde with glutaraldehyde to fix the cells and after replacing the fixative with PBS or imaging buffer vortex 100 nanometer gold particles and add 35 microliters per well for tracking stage drift During imaging.

Approach the microscope and power on the 405 and 561 nanometer lasers keeping the shutters closed at this point, ensure the 561 nanometer dichroic mirror and notch filter are in place. Open the image acquisition software. Turn on the E-M-C-C-D camera and allow it to cool down and set the exposure time to 100 milliseconds and the E-M-C-C-D gain to an appropriate value.

Add immersion oil to the objective and secure the sample on the microscope stage age. Next with either brightfield or the 561 nanometer laser, bring the sample into focus for imaging RAs and other membrane proteins. Use a 60 x APO chromat turf objective with a 1.49 numerical aperture and bring the microscope into turf configuration.

Adjust the excitation laser so that it is off-centered when hitting the back aperture of the turf objective, which will cause the laser to deflect upon reaching the cover slip buffer into face. Keep adjusting the laser incident position until the critical angle is reached and the laser is being reflected back. Search for a cell to image with several gold particles in view.

Then set a region of interest that encloses the cell or a region of it and the gold particles in case sufficient activation is already occurring because of high expression levels. Begin acquisition with the 405 nanometer laser off and the 561 laser on. Otherwise, turn on the 405 nanometer laser at the lowest factory power setting and increase it gradually until there are tens of molecules per frame or so that single molecules are well separated.

As data acquisition continues, gradually increase the 405 nanometer laser power to keep the spot density roughly constant. Continue image acquisition until high 4 0 5. Power does not initiate any more.

Activation events ends to process images. Download the image processing software. Open MATLAB and load the WFI read software.

View the raw image sequence and determine the region of interest or ROI select the area of the stack to be processed by left clicking and dragging a box around the desired area. If the region of interest was not reduced during acquisition, select a smaller area to lessen the computing time to deselect an area and process the entire frame right Click anywhere in the image next to define a set of fiduciary markers such as gold nanoparticles absorbed on the cover slip that are well isolated, uniform and shape and present in the field of view throughout the image stack. Start by selecting a candidate gold particle by left clicking on its image and dragging a small box around it.

Under particle tracking, click the track button. A graph will appear that shows the position of the selected gold particle across the stack of images depicting the extent of the drift. Repeat this process to track as many gold particles as possible and determine the particles that track together.Ideally.

The overall drift is on the magnitude of 0.1 pixel at the most, one at a time. Select the gold particles that tracked together and under particle tracking. Click the add marker button.

A green cross will appear signifying that the particle has been added as a marker and will be used to correct for drift. Adjust the sigma range smoothing range and threshold as necessary by changing the value slightly. Click the find particle button to test the settings and visually inspect process particles such as the PAM cherry one molecules that are relatively round and bright will be boxed and those that are not will be left out.

To start processing the images, click the make cord file button and save the file under a desired name to post-process the images and render the palm image. Launch the palm package in MATLAB load the dot core file just created. A coursely rendered image will appear in the image box next to the control buttons.

Sort the individual coordinates using the following typical values. For PAM Cherry one, combining frame equals eight. Combining distance in nanometers equals 100 minimum RMS equals four.

Minimum fit goodness equals 0.25 and max eccentricity equals 1.4. Click the sort button to generate a new set of curated coordinates ready for rendering high resolution images. Enter values for proper rendering of the final image, such as the raw pixel size as previously determined the desired feature size in the rendered image, which is normally set at a value slightly higher than the average localization and the pixel size such as 10 nanometers.

For the rendered image, click the render button to generate the palm image. Then use the plus and minus magnifying icons in the toolbar of the figure window to zoom in and out to track single molecules in live cells. Treat the tissue culture surface and plate the cells as described earlier in this video.

Ensure that the cover glass has the appropriate thickness for the microscopy set up after transecting cells and performing any treatments and incubations needed for the experiment, place the culture dish on an onstage incubator. Allow the dish to settle on the stage for a few minutes until the temperature and CO2 concentration stabilize at this step. Block the lasers.

If CO2 control is not available, change to a CO2 independent medium right before imaging such as leibovitz's L 15 to depress background fluorescence finally acquire images as demonstrated earlier, setting an appropriate exposure time to ensure good signal to noise ratio without losing time resolution. The BFC palm in this figure is the KRAS G 12 D mutant interacting with the RAs binding domain or RBD of CRAF. Each of the four combinations shown here were introduced into U2 OS cells using lentiviral infection cells with two of the configurations had strong positive BFC signals as identified by the abrupt increase in fluorescence when the 405 nanometer laser was turned on due to the photo activation of BFC reconstituted PAM Cherry one as demonstrated here using the same experimental settings as with the parent PAM Cherry one.

A strong BFC signal was generated after infection with RN R and RAF RBD RC.Here, RN and RC denote the n and C terminal fragment of PAM Cherry one respectively when zoomed in individual molecules and their nanoscale spatial distribution can be clearly seen in this experiment where single molecule tracking palm was performed to acquire diffusion trajectories of individual RAs. RAF RBD complexes under continuous illumination with 561 nanometer and 405 nanometer lasers. Individual PA m cherry one molecules st.

Switch on and last a few frames before entering dark states where they were found to be either immobile or mobile. This plot of recordings for multiple molecules clearly illustrates both types of trajectories. The same heterogeneous distribution of diffusion states can be inferred from the histogram of molecule displacement between successive frames Mass mastered.

This technique can be done in one to three weeks, depending if the constructs are transcendently, transfected, or stably oppressed if it's performed properly. While attempting this procedure, it's important to remember to prepare controls such as mutant Putins that lacks the interaction following this procedure. Other methods, like a cluster analysis can be performed in order to answer additional questions like, how is the protein interactions spatially organized in the cell?

For lab cell tracking, evaluational base, single particle tracking can be performed to determine diffusion states and the transition probabilities after its development. This technique is being used in our lab in the field of cancer biology to explore RA drive interactions as well as the homo and the ization of her family receptors in human tumor cells. After watching this video, you should have a good understanding of how to design and implement a biopsy palm s to investigate a protein interaction of interest.

Don't forget that working with antivirus and the tumor cells can be extremely hazardous and precautions such as the standard bio safety protocols should always be taken where performing this procedure.