High performance capillary electrophoresis - T.E.A.M.

Modes
smaller mesh spacings (or pore sizes) and is used for
protein separations. The larger mesh spacings of the latter
are more suitable for DNA. In the slab or tube, these media
are not only used to effect a size separation, but also
because they are anticonvective and can hold their own
shape. This latter requirement limits the minimum concentration
and also the possible compositions of gels that can
be used. As mentioned, this limitation is relaxed by the anticonvective
nature of the narrow-bore capillary.
Use of the term “gel” in CGE is somewhat ambiguous. A
gel usually implies a solid-like structure as used in slab-gel
electrophoresis. Since many of the “gels” used in CGE do
not (and need not) possess this property, a more suitable
term may be “polymer network”. Polymers in CGE can be
covalently crosslinked (such as bis-polyacrylamide),
hydrogen bonded (such as agarose), or linear polymer
solutions (such as polyacrylamide or methylcellulose).
Although the polymer structure of the uncrosslinked gel is
radically different from that of crosslinked gels, the mechanism
of separation is identical. Subsequently, macromolecules
can be size-separated using either gel type (table 15).
Polymer Concentration Application
Crosslinked polymers
Polyacrylamide/bis- 2– 6 % T, 3 – 6 % C ● Oligonucleotides, DNA
acrylamide
sequencing,
● Native and SDS-bound
proteins
Linear polymers
Polyacrylamide < 0.1– 6 % ● Restriction fragments
Hydroxylalkyl cellulose, 6 –15 % ● Oligonucleotides, DNA
polyvinyl alcohol,
sequencing, proteins
dextran
Table 15
Polymer matrices for CGE
Agarose 0.05 –1.2 % ● Restriction fragments
● Proteins
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