User:Brian P. Josey/Notebook/2010/06/16

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Closer Look at Ferritin emulsions

I created two new flow cells of the ferritin emulsions today. The first emulsion I created, I put into the microscope and filmed both with and without the influence of a magnet. For the second emulsion I created, I let it sit in the magnetic yoke, to see if it could aggregate in a similar manner to pure ferritin in solution. This process lasted for 45 mins, a little shorter than the standard time I took to aggregate ferritin alone.

First Flow Cell

I placed the first flow cell onto the microscope stage, and filmed it three times. The first instance I used it as a control, and filmed it for two minutes without any exposure to any magnet. This allows me to see the natural Brownian motion at this scale, and use as a reference. Here is the film:

As expected, the water droplets move around in random motion, and do not all go in one direction or another, but remain relatively close to their starting position. Given more time, they should diffuse throughout the flow cell. Of course, because the motion is so slight at this level, I sped the film up by removing frames. This makes the motion much more pronounced, but gives a more useful video. The added speed makes it easier to keep track of the general trend, and any net motion. At this point, the basic idea is more important than the fine details. All of these films are significantly slowed for this argument. Later, when I get it working and I begin tracking and collecting data on the speed, the fine details will be more important.

The second time, I rested the edge of one of the small cone magnets on top of the slide. The magnet has a strength of 50 MGOe, and was placed so that the leading edge of the base was tangent to the film of view, and as close as possible without obscuring the vision. Here is the video of this test:

The magnet was placed on the left side of the slide, which is conveniently the left side of the image also. While some of the droplets appear to be moving over to the left side, the white oblong droplet about a third of the way down the image on the left side is a good example, there is not enough motion from enough of the droplets to make a clear case for the motion. It may also be possible that I am not letting the experiment run long enough for any net movement to become obvious. It will be worth it to let the experiment run for a longer time frame, on the order of 10 mins to even 30 if necessary.

The third time, I attached the cone magnet from above to a 1/2 in diameter cylinder magnet with a strength of 40 MGOe and a length of 2 inches. At first, as in the case of last week where I failed to write down the orientation of the magnet, I assumed that it would be easier to hold the magnet on the left side, nearer to the computer. But because I am right-handed, holding it on the right side was more comfortable, and as a result, all experiments with this magnet have a field pointing towards the right of the image. Video:

Once again, it is impossible to notice any overall tend towards the right, and it appears that all motion is random. The major difficulty with this is that it is difficult to hold the magnet in a certain spot for two solid minutes, and not deviate in position or direction. Touching the magnet to surface of the flow cell unfortunately alters the optics and shaking from my hand makes it impossible to focus clearly on the image, so holding the magnet above the slide was the best choice. However this resulted in the obstruction and changes in optics in the film. I clearly need to mount the magnet to the microscope soon.

Second Flow Cell

For the second flow cell, I placed it in the magnetic yoke as I have done before for similar experiments with pure ferritin in water to see if any aggregation would develop in the droplets, and if so how it would act. After leaving it in the yoke for a solid 45 mins, there was no obvious visual aggregation. Checking under the microscope revealed a small dark clump about 1.5 field of views in diameter. It appears that the droplets did aggregate in a small amount. Here is the spot under the influence of the cone and cylinder magnet at the right of the video:

The structure appears dark as a result of the diffusion of light from its larger three dimensional structure. It also seams to have both small and larger droplets as its composition, suggesting that given enough time the droplets can merge, or that they were not all broken down when prepared in the sonicator. As before, there was no obvious general trend to the right of the image, towards the magnet. While the central mass did not move even in the slightest, there was still pronounced Brownian motion in all the other droplets. For comparison, I found a relatively sparsely populated area in this flow cell and repeated the experiment again:

In this case, there appears to be a general upward trend, pay close attention to the lower left corner to see the most obvious case. However, this is not conclusive evidence of the magnetic force having any real and concrete effect on the droplets. The magnet was held to the right of the image, although it is possible I was holding it higher than I thought, or I may have been pushing against the slide holder without realizing it. It's encouraging, but illustrates that I need more time, and a mounted magnet to make more meaningful results.

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