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Please log me off!!At 09:33 11/30/04 +0000, you wrote:
>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal    Dear  all,
>on that from  experience?     JP also asked to  give some numbers about
>actual light doses in the bleach phase of a FRAP  experiment. I'll give it
>a try:     area is H*t, where t is the time of  illumination.    the
>bleached area and D the  diffusion coefficient.    2) with a scanning laser
>beam on a confocal  microscope. An example:     the characteristic recovery
> time is tau = 25 ms and hence the bleach time approx. 0.25 ms. For a
>typical  bleach power of 1mW the total energy recieved per unit area is
>therefore  1mW/(pi*1mum^2)*0.25ms = 80 kJ/m^2.    the scanning speed  of
>the laser beam and dy the distance between the adjacent scanning lines (see
> our article on FRAP for details). v and dy depend on the zoom setting of
>course,  but will be typically in the order of: v = 0.1 m/s and dy = 0.2
>mum. Hence, the  total amount of energy per unit area is:
>1mW/(pi*1mum^2)/(0.1m/s*0.2mum) = 6  J/m^2.   As this little  calculation
>shows, it is much more likely to inflict damage to your live cell  when
>doing spot photobleaching, compared to scanning photobleaching. Luckily,
>hardly anyone is still doing spot photobleaching experiments I  guess.
>To relate them to actual damage  to a particular structure in the cell, one
>would have to take the absorption  cross section (wavelength dependent)
>into account. Does anyone have any data on  that?   Best  regards,   Kevin
>   Kevin Braeckmans, Ph.D. Lab. General Biochemistry and Physical  Pharmacy
>Ghent University  Belgium
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Daniel Mackay, B.Sc., FRMS, AIBMS
Advanced Microscopy Unit/Drosophila Laboratory
Section of Old Age Psychiatry/Department of Neuroscience
Institute of Psychiatry
De Crespigny Park
Denmark Hill
London
SE5 8AF
0207 848 0553 - office
0207 848 0554 - Microscopy Suite
0207 848 0119 - Drosophila Lab.

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