cent molecule of interest which is uniformly distributed throughout the cell.
How many molecules of the fluorescent molecule are there  write an equa
tion that gives this number?
Before doing any calculations, explain what
the final concentration
c
∞
will be after infinite time, when the system has
returned to equilibrium.
You may assume that once a molecule has been
photobleached it is effectively dead and can be forgotten. Your goal now is
to compute the recovery curve. What this means is that you need to work
out how many fluorescent molecules are in the photobleached region as a
function of time. Make graphs for the case where the photobleached region
is centered about the origin. Make sure when you make your plots you use
reasonable values for the diffusion constant  justify your choice. One of the
uses of the FRAP technique is to determine the diffusion constant of various
molecules within the cytoplasm of cells. Discuss how that might work on the
basis of the derivation you have given here. To do this problem you will need
1
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the table of zeros of the first derivative of
J
0
(
x
) given in the file attached to
the homework. Make sure you explain exactly what you are doing and what
your results mean. Also, I want you to plot the result for different number
of terms kept in the Bessel series. Use just enough terms in the Bessel series
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 Winter '09
 Nicotinic acetylcholine receptor, PBOC, photobleached region, ﬁnal concentration c∞

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