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filters: you may be loosing lots of green fluorescence if you have too many
or suboptimal filters in the EPICS. For example, a good 6 cavity bandpass
filter 530BP30 (i.e., a 30 nm wide band centered on 530 nm) will eliminate
488nm scatted light and let through green without the need for a laser
blocking filters. Remember: more glass, less light. You want your work to be
illuminating, don't you? (Sorry, I'm ready to leave for vacation.)
electronics: FACScan has a 4-decade log amp; the EPICS C has a 3-decade log
amp. The distribution of populations will be different.
If you crank up HV, however, you should be able to see positives and
negatives if they really are there. Not having an illustration of the prior
analysis makes it harder figure out. I'd ask for one, it may help
Dave Coder
dcoder@u.washington.edu
Begin forwarded message:
Date: Thu, 22 Dec 94 08:34:54 PST
From: "Susan D. DEMAGGIO" <SDDEMAGG@uci.edu>
Encoding: 686 Text
To: cytometry@flowcyt.cyto.purdue.edu
Subject: FACScan vs EPICS
Fellow Cell-Mates
I wondered if this is a common problem and what might be the solution. I just
attempted a sort for someone who found a population of expressing T cells (Don't
know what protein) of about 8% positive green fluorescence by FACScan analysis
(he did it at his facility so I don't know anything about how bright they were.)
I couldn't identify them anywhere on the EPICS (I admit it is old and the laser
is LAZY - but they should have been there - shouldn't they have??) I'd like to
help him (and my facility needs the money!!). Any tips on how to identify that
population? Or is my sorter just not as sensitive as the SCAN??
SUE DeMaggio
UC Irvine
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