In article <36DE9C3A.D496052 at pitt.edu>, rdudley+ at pitt.edu wrote:
> Wiebke Schmidt wrote:
>> > I want to compare the activities of several mutants of an enzyme. In the
> > assay immunoprecitates of the enzyme are used. I have problems in using
> > equal amounts of immunoprecipitate in each assay because of the
> > consistence of the protein A-Sepharose (PAS). Does anyone have a
> > suggestion how to pipette equal amounts of PAS?
> > Thanks in advance,
> > Wiebke
> I cut the end off of a 200 ul tip and use that. Works fairly well.
> rich
I agree. For smaller amounts and extra accuracy I pellet an
aliquot of the slurry and take off the liquid and then weigh
out the "solid". I've seen other people flash freeze the
slurry solution and then weigh chunks of the solid (quickly).
For even greater accuracy I think we'll be counting individual
beads... :-)
Bernard
--
Bernard P. Murray, PhD
Dept. Cell. Mol. Pharmacol., UCSF, San Francisco, USA
