Atomic Force Microscopy van Red-Light Fotoreceptoren behulp PeakForce Kwantitatieve Nanomechanical Property Mapping

The overall goal of this procedure is to collect high resolution images of photoreceptor proteins using atomic force microscopy. This is accomplished by first obtaining a sample of the photoreceptor and diluting it. The second step is to apply the protein sample to a freshly cleaved and clean mica surface for about 30 seconds.

Then the MICA is rinsed with buffer to remove unbound and loosely attached molecules. Next, the sample is attached to a liquid cell that is equipped with an appropriate probe. This assembly is loaded onto the scanner.

After filling the liquid cell with buffer solution, engage the tip with the sample and begin scanning. Ultimately, atomic force microscopy incorporating peak force. Quantitative nano mechanical property mapping is used to collect images of single photoreceptor protein on the sample surface.

Atomic force microscopy that incorporates peak force q and m can answer key questions in the field of molecular biology, such as what are the important structural and chemical characteristics that determine the function of biologically active macromolecules. The main advantage of this technique over current methods such as NMR and X-ray crystallography is it high resolution images of intact proteins and other biological macromolecules can be obtained in a biologically relevant environment. Generally, individuals who are new to this method struggle because the tuning of the probe and solution requires multiple steps, some of which are quite complex.

With peak force q and m and automated software, several of these steps are made simpler, thus making the process much easier for new users and undergraduate students. Demonstrating this procedure will be three undergraduate students from my research laboratory, Marie Kroger, Blair Sorenson, and Jessica Thomas. These students will be pursuing graduate studies in the fields of microbiology, chemical engineering, and chemistry this upcoming year.

These items must be turned on in a specific order. First, the computer, then the controller, and lastly, the fiber optic light. The microscope needs to be reading a FM and LF fm.

The camera must be centered over the a FM optical head in the software. The following should be selected. The experiment category is mechanical properties.

The experiment group is quantitative nano mechanical mapping, and the experiment is peak force q and m in fluid. With the settings correctly selected, the experiment can be loaded and set up. The camera focus should be set using the Z objective first, followed by using the course controls to position the stage, the goal is to place the A FM head aperture one millimeter before the stage surface to manipulate the sample discs with freshly cleaved mica have circular disc gripper tweezers.

Begin with assembling the fluid cell from pristinely cleaned parts. First, attach the hose adapter to the port on the clean fluid cells. Then using flathead tweezers very gently, press the O-ring into its indentation on the fluid cell.

Next on the probe retainer clip, press the spring lightly and turn it away from the groove. Using the same tweezers, grip the probe and slide it into the groove, so the tip faces the center of the cell. Then secure the probe using the clip.

The next step is to check the clamp on the A FM.It must be fully retracted. Place the assembly facing downward on top of the sample. Fit the assembly onto the studs of the A FM for stabilization.

Lower the clamp. To inspect the O-ring, press the down switch on the microscope until the O-ring is seen. It should be firmly compressed between the support disc and the fluid cell.

The fluid cell can be put into focus using the coarse adjustment knob. Next, using the XY adjustment, focus on the probe tip. It looks like a metallic golden triangle.

Now using the down pizo lever, move the tip close to the sample surface, adjust the focus onto the tips, reflection, and monitor the cantilevers position in relation to this reflection. Presently, they should be closely aligned but not completely overlapping. Now, prepare the syringe.

Fill it with one milliliter of buffer solution and attach the adapter. Then attach the syringe to the ejection hose and fully extend the plunger. Next, attach the hose to the fluid cell using an adapter to fill the chamber, gently press the plunger until the center of the chamber is full.

There should not be any air bubbles or spilling from the fluid cell onto the microscope. Then place the syringe in a well-supported position above the chamber. Next, use the camera feed and XY translation knobs.

To locate the laser on screen, it should appear as a diffuse red dot. Once located, use the laser controls to move it to the probe. Now finally, adjust the laser and mirror controls until the sum signal on the microscope is maximized to between four and six, adjust the quadrant diode.

Next, use the knobs on the scan head to adjust the vertical and horizontal deflections until the values on the microscope return to as close to zero as possible. Be sure to select appropriate acquisition options before proceeding. Set the scan rate to about one hertz in the samples per line window.

Enter 256. For the scan assist auto control. Select individual for the scan assist auto Z limit select off.

The Z limit should be 500 nanometers, and the scan size should be one micron. With the settings correctly set, gauge the probe. Observe the Z pazo voltage change as the probe tip approaches the surface.

If the tip goes outside the range, withdraw and reapproach, the probe tip may have to be replaced. If this doesn't work, when the tip is engaged, lines should appear on each of the acquisition windows, and these lines will construct an image. Begin continuous capturing of images of the mica.

Slowly zoom in to ensure that the MICA surface is both flat and clean. Prepare a four chamber Petri dish with refrigerated imaging buffer solution. Each chamber needs at least five milliliters.

Before taking an aliquot of diluted protein, gently stir it with the micro pipette. Then take a 200 microliter aliquot and apply the diluted protein to the MICA surface. Wait about 30 seconds for the solution to reside on the surface.

Then using the disc grippers, lift the disc without tilting it and immediately immerse it in the first pool of buffer solution. For one second, make certain the disc stays parallel to the bench. It's very important to keep the sample parallel to the Petri dish during the rinsing step.

These soft, flexible molecules can be distorted on the surface by strong currents of aqueous solution. Next, briefly immerse the disc in each of the other three pools for one second per pool. Then transfer the disc to a dry and dust-free cloth.

Let the excess moisture transfer to the cloth, but don't let the disc dry completely. Do not allow the cloth to touch the sample Carefully remove the sample from the cloth with the disc grippers and place the sample onto the A FM scanner. Place the fluid cell on top of the sample and proceed with the setup and imaging.

After all the parameters for the probe, the spring size and tip radius are properly set. Gauge the probe as when imaging. Micah, observe the ZP azo as the tip approaches the surface.

When taking images, allow the scanner to image the same area for at least two consecutive passes. Use continuous capture to save each image. Adjust the image size and location as desired.

Once the automated software has finished adjusting the scanning parameters for a particular image size. Turn the software off to fine. Tune the focus of the image manually adjust the scan rate the Z limit, the number of lines and the set point.

If the image becomes too unfocused, turn the software back on to return to the original starting position. While zooming in on a protein, decrease the scan rate and increase the number of lines proportionally in order to increase the resolution of the image.Later. When analyzing the images, first, flatten the image by clicking on the flatten icon.

Select the zeroth order and execute the operation. Sometimes it is necessary to use a plain fit to obtain appropriately flat images. Select the plain fit icon and use the cursor to draw a plane over a flat area in the image.

Execute the plain fit and repeat the operation as necessary. Next, select the cross section tab to measure the dimensions of the protein. Draw a line with the cursor over the molecule or area to be analyzed.

Repeat this process in multiple areas. If an overlay is desired, any number of biological molecules can be studied using a FM for a photoreceptor protein in its light adapted state, a freshly cleaved micas substrate is a suitable flat surface for protein absorption. Single photoreceptor protein dimers were observable using the peak force QNM mode.

The arrows point out individual dimers and the asterisk denotes a protein aggregate using image analysis software. Cross sections of the proteins may be measured after the image is flattened. XY data correlate to the height measurements.

These can be used for a variety of calculations. After watching this video, you should be able to set up an A FM experiment to collect high resolution images of proteins on a surface in a biologically relevant environment. Using peak force q and m Once mastered, this technique can be performed in approximately three to four hours.

Therefore, peak force q and m is an appropriate form of atomic force microscopy to introduce to undergraduate students enrolled in laboratory courses such as instrumental analysis, biochemistry, and modern physics. After its development, this method pave a way for researchers in the field of scanning probe microscopy to explore biological molecules such as proteins, nucleic acids, and even live cells in biologically relevant media.