Many thanks for the responses to the query concerning beam diameter.  For
the curious, a beam diameter measurement (in the x-y plane) will be useful
to us because we are trying to measure punctate sources of fluorescence on
the cell surface (coated pits) and extrapolate the number of spots observed
to a whole cell surface.  For anyone who may have a similar need, a very
useful paper that I ran across since my initial posting  relates beam
diameter to pinhole setting specifically for the Bio-Rad MRC-600, 488 nm
excitation, 60X/1.4NA objective by measurement across a sharp gold edge -
see Petersen et al., Biophys. J. 65:1135-1146 [1993], Fig. 3.
 
Thanks again,
Jim Keen
 
 
James H. Keen, Professor
Dept. of Pharmacology and the
Jefferson Cancer Center
Thomas Jefferson University
233 S. 10 St., BLSB/915
Philadelphia, PA 19107
 
215-955-4624
215-923-1098 (FAX)
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