Bio-Rad Affi-Gel 15 Gel User Manual
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will repel negatively charged proteins (proteins buffered
at a pH above their isoelectric point) and lower their cou-
pling efficiency. The Affi-Gel 15 support, due to the ter-
tiary amine incorporated into its arm, has a slight overall
positive charge, and the effects are reversed.
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The Affi-Gel 10 support couples proteins best at a pH
near or below their isoelectric point, and the Affi-Gel 15
support couples proteins best near or above their isoelec-
tric point. Therefore, when coupling at neutral pH (6.5-
7.5), the Affi-Gel 10 support is recommended for proteins
with isoelectric points of 6.5 to 11 (neutral or basic pro-
teins), and the Affi-Gel 15 support is recommended for
proteins with isoelectric points below 6.5 (acidic pro-
teins). See Table 1.
The difference in coupling efficiency of the Affi-Gel
10 and Affi-Gel 15 supports for acidic and basic proteins
can be attributed to interactions between the charge on the
protein and charge on the gel. Hydrolysis of some of the
active esters during aqueous coupling will impart a slight
negative charge to the Affi-Gel 10 support. This negative
charge will attract positively charged proteins (proteins
buffered at a pH below their isoelectric point) and enhance
their coupling efficiency. Conversely, the negative charge
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