pI determination methods for QC

StewJW via methods%40net.bio.net (by stewjw from gmail.com)
Tue Jan 20 05:11:04 EST 2009

Invitrogen do offer the precast Novex IEF gels which are used in their
standard Surelock appararatus but they range from pH 3-10 or pH 3-7.
For crude estimation there are also IEF markers in the 3.5 - 10.7

The IPG (immobiliased pH gradient strips) Runner system you mentioned
is designed for running 2D gels of a large number of samples. There is
a gel strip holder, IPGRunner Cassette, which fits inside the
Invitrogen Surelock mini-gel apparatus. Each cassette can hold upto 6
(7cm) strips. The strips come in the following pH ranges:

ZOOM® Strips pH 3-10NL 12 ZM0011
ZOOM® Strips pH 4-7 12 ZM0012
ZOOM® Strips pH 6-10 12 ZM0013
ZOOM® Strips pH 4.5-5.5 12 ZM0014
ZOOM® Strips pH 5.3-6.3 12 ZM0015
ZOOM® Strips pH 6.1-7.1

After running the IEF strips they are individually removed and placed
long ways inside an insert of a precast ZOOM® Gels, which are  are 8 x
8 cm, 1.0 mm thick pre-cast polyacrylamide gels to run the second


I've never used this, and I'm unsure how practical it is to excise
small samples from gels to measure their pH in solution. Thermo-
Russell sells a small Ag/AgCl combination electrode which can measure
down to 50µl of liquid, catalogue number: CMAW711/4/5/SC; dimensions
below cap are 90mm x 5.5mm. See www.thermo.com/russell. I should say I
work for Fisher UK a ThermoFisher company so I'm a little biased in my

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