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> I wanted to confirm that the data rate would be proportionate to the
> concentration of beads in a sample.
Kris: I suspect the deviation from linearity you observed on your Elite is
due to the electronic 'dead time' required for processing of each event.
When an event exceeds threshold, there is (I deduce from your and my data)
a certain processing time window during which additional events will be
ignored. I have similar data (but with losses occurring at even lower
rates) for our FACScan using the OLD HP 310 Pascal 3.1 computer with
'FACScan Research Software 1988' as the acquisition software.
Live rate displayed Rate saved to file Events lost
on monitor to disk file
3,200/sec 294 91%
420/sec 357 15%
Since the rate saved is actually slower at the higher rate, there is
evidently a penalty for higher rates above and beyond the dead time
per recorded event. I think everyone should do the kind of check you
did. The conclusion (for our setup) is that concentrations of cells
giving rates above 500/sec are simply wasting cells!
It would be useful if B-D and Coulter would post some specifications
for the various instrument models and acquisition software packages (and
include them in their manuals!). [B-D, Coulter, &c consider this a formal
invitation to give us some authoritative info here!]
/*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Eric Martz, Professor of Immunology emartz@microbio.umass.edu
Dept Microbiology Voice: 413-545-2325 FAX: 413-545-1578
Morrill IVN 203, Box 35720, Univ Massachusetts, Amherst MA 01003-5720
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/
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