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If you assume the on-rate is diffusion limited and the off rate given 
then by the Kd (koff/kon), is the change in rate of rise consistent with 
the expected change in kinetic properties? Note that the time constant 
of response of the dye is = (kon.Ca + koff). In cardiac cells, I would 
say that the reduced rate of rise is probably due to the time it takes 
for diffusion to occur through the (restricting) nuclear memrane (i.e.  
Fick's first law of diffusion).

Hope this helps,

Mark Cannell

Pedro J Camello wrote:

>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Hi,
>
>I would like to listen opinions regarding compartimentalization of
>fura-2 in cell nucleus. I know of some reports of accumulation of fluo-3
>within nucleus, which was accompanied also by changes in the calcium
>affinity of the dye. I have observed that nuclei of fur-loaded cells
>have a stronger  fluorescence than cytosol, but the resting is slightly
>lower. I guess is just a change in Kd, but I have observed that both the
>rate of Ca2+ rise and the propagation of cytosolic signals within
>nucleus is slower than in cytosol. If there is just a Kd increase, could
>it explain that slowed kinetic?
>Thanks
>
>
>  
>