Last time, I just briefly wrote about the problem we had when we calculated diffusion coefficients. We were off by a factor of four. After consulting the camera's manual it turned out, that the camera does different "binning" of pixels in the mode we use for particle tracking. "Binning" means, that two pixels become one in the final image. Thus, a 1024*1024 px*px image shrinks to a 512*512 px*px image. And if you think that 6 px represent one micrometer and you do not know about the binning, it's actually 6 px being two micrometers! As the distance goes squared into the diffusion coefficient, we got our factor of 4, yay! (But never mind the software explicitly saying that there is no binning for this camera type, haha... it's only on page 60 of a 130 page manual ;-))
So my life was pink again; I continued with another experiment where we want to observe the growing and shrinking of cell polymers (microtubules). I mixed the cocktail for the experiment and was happy to image lots of moving rods (that's how microtubules look like). But after thinking about it... diffusion could make them move in a super similar way! Damn it. Even theoretical estimations show that they could move quite a bit in 30 seconds. Fortunately, there are different dyes out there to label the dynamic part (growing and shrinking) and the static part (our seeds), so we'll hopefully understand what's actually happening.
