Wednesday, May 04, 2011

Diffusion in cells

Diffusion in cells- been teaching the course bio435 - biophysics II or Physical Biology of the Cell or what i really do for a living or...
The fascinating part about diffusion is that it binds both historically and scientifically energy, matter and living-systems. Brown who discovered brownian motion was looking at pollen grains. Einstein who described the relation between macroscopic viscosity and molecular movement is "the physicist".
Using fluorescence recovery after photobleaching, some simple imageJ data extraction and loads of attempts at analyzing the data, we find a few odd things.
A FRAP profile of an E. coli cell expressing GFP

1_ GFP diffuses faster in the E. coli than we can bleach it out.
2_ Reducing the number of bleach pulses doesn't allow any measurable bleaching, i.e. our scanning system is too slow
3_ The recovery kinetics show heavy amounts of imaging-dependent bleaching. Did we not turn down the laser after the bleach?