Ion Exchange Chromatography

The isoelectric pH of immunoglobulins (approx 8.6) is higher than the majority of the other serum proteins. As a consequence, they will be among the few proteins that will not bind to anion exchange media at neutral pH, providing a rapid an effective means of purification, particularly if combined with precipitation methods such as ammonium sulphate fractionation.

Agarose-based exchangers are the most convenient to use because of their good flow properties and the most versatile of these is the diethylaminoethyl (DEAE or DE) derivative. The cellulose-based equivalent can also be used but in addition to having lower flow-rates/higher back-pressures it is advisable to precycle these before use (see Note 13). The subsequent protocol describes a column-based procedure, but a batch method could also be used, using filtration or centrifugation to separate the antibody containing supernatant from the ion-exchange medium.

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