Re: Purity of sorted populations
FACS_COPY@wehi.edu.au
Fri, 31 Mar 1995 12:37:13 +1000
I'm entering this sort purity discussion late because I've let the
mailing list get a bit ahead of me lately but I had to put in my 5
cents worth. Mario has already made many good points I agree with
(although I can't accept that his vertical sort procedure gives
uncharged droplets; altering the deflection plate balance won't affect
the droplet charge). But going further from what has already been
said, I would assert that running faster will not, in itself, lower
the sort purity if the sorter is doing coincidence checking; it may
only increase the rate of occurrence of doublet events where a cell,
negative for the marker you are sorting for, rides along as a
passenger into the collection tube (hence the benefits of the "dump
channel" already alluded to). If you are sorting cells which are
negative for everything, then the only passengers must also be
negative and there's no reason you can't aim for three-nines (99.9%)
purity NO MATTER HOW FAST YOU SORT. Going faster should only lower
the recovery.
On the question of assuming 100% purity: As Felix Unger once said "If
you ASSUME, you make an ASS out of U and ME." Too many things can go
wrong during the sort, like blockages that contaminate the sorted
fractions and then clear themselves before you've noticed (even while
you're tilting your head to pour in some coffee). I therefore
strongly endorse the suggestion of re-analysing all sorted fractions.
Regards to all, | | < Frank: battye@wehi.edu.au
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