Frederick Garbrecht fgarbrec at POST.ITS.MCW.EDU
Sat Feb 27 21:19:34 EST 1993

Many of the iodination protocols I have seen (and used) suggest doing a
TCA precipitation to quantitate the amount of incorporated label.  Problem
is, nobody ever gives a suggestion as to what kind of numbers represent
efficient labeling.  Does anyone have any guidelines?  For example, if you
were surface labeling mammalian cell proteins, what kind of incorporation
(in cpm per mg protein or cpm per million cell equivalents) would be
reasonable to expect?  If you were then to use a lysate of that
radiolabeled preparation in an immunoprecipitation, how many cpm would you
use per precip?  I have not routinely monitored label incorporation, (I
wish I had), but I have a bad feeling that my labelings are frequently not
at all efficient, but I don't know how to interpret the TCA numbers that I
get (when I do them).  Any comments appreciated.  Thanks.

Fred Garbrecht
Medical College of Wisconsin
fgarbrec at

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