Bio-Rad Model 491 Prep Cell and Mini Prep Cell - Manual (Page 40)

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Fig. 16. Selecting a native electrophoresis buffer system.
Determine the pI of the protein
under investigation. Isoelectric
focusing is recommended for
this purpose.
Determine the pH
range where the
protein retains its
biological activity.
NO
Ornstein-Davis buffer system
(pH 9.5) should not be used
because:
1. The protein of interest will
denature due to high pH.
2. Or, the protein of interest
will carry so little net charge
that it will not migrate
through the gel.
3. Or, the protein of interest
will carry a positive charge.
Is the pI of the pro-
tein below pH 8.5?
YES
NO
YES NO
YES
Is the protein stable at
pH 9.5?
Does the protein precipitate
at the interface of the
stacking gel and resolving
gel?
Ornstein-Davis system can
be used. For reagent
preparation and running
conditions refer to Section 3.
A. Use a different
discontinuous system of
appropriate pH. (See
Chrambach and Jovin
1984)
B. Select a continuous buffer
system (McLellan1982) of
appropriate pH. See
Section 4.
Run the sample containing
the protein to be purified on
mini-slab gels using the
discontinuous system of
Ornstein and Davis. See
Section 3.
or