User:Brian P. Josey/Notebook/2010/07/06
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Last week, I created and filmed an emulsion of ferritin in mineral oil, and I used it as a basis to check for and measure the forces that a magnet exerts on the ferritin. On Thursday I posted the footage and general paths that I traced from watching the films. It is clear that the magnet does exert some kind of force on the ferritin, and that without it, the emulsion droplets travel in random directions. However, I wanted to get a good feel for the magnitude of the forces, and to get a basic idea for future projects.
On Friday, using the above picture, I measured out the length of the arrows that I created by attaching the starting and ending positions of twenty-five different droplets, and their average diameter. With the arrows, I could calculate the average speed at which the droplet travelled, and for how far it traveled over the two minutes of filming. While the arrows do not all point directly at the magnet, there is some side to side drifting, I measured the full length of the arrow and substituted it as the total path resulting from the influence of the magnet. It would be more correct to measure only the displacement in the up-down direction between the start and finish. For the diameter, I measured the diameter of the droplet in the final and initial image and used them for an average. After converting the units of measurement I was able to calculate the number of ferritin molecules in a droplet, the average force on the droplet, and the force for each ferritin protein:
From the data it is clear that the ferritin droplets are fairly large, having a radius on the order of a micron, and that the force on the ferritin, and in turn the droplets is actually not that strong. It is so small compared to other numbers that I calculated because the magnet is smaller and farther away than I’ve had in my simulations.