{"id":1722,"date":"2021-06-02T10:17:25","date_gmt":"2021-06-02T10:17:25","guid":{"rendered":"https:\/\/www.embl.org\/groups\/protein-expression-purification\/?page_id=1722"},"modified":"2021-06-02T10:26:37","modified_gmt":"2021-06-02T10:26:37","slug":"ion-exchange-chromatography","status":"publish","type":"page","link":"https:\/\/www.embl.org\/groups\/protein-expression-purification\/services\/protein-purification\/ion-exchange-chromatography\/","title":{"rendered":"Ion Exchange Chromatography"},"content":{"rendered":"\n
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The aim of ion exchange chromatography (IEX)<\/strong> is to separate proteins based on their differences in net surface charge<\/strong>.<\/p>\n\n\n\n

The pH at which the IEX will be performed depends on the pI<\/strong> of the protein of interest and the differences between the target and contaminant proteins. When the pH equals the pI, the protein has no net surface charge. At a pH above the pI, the protein will be negatively charged and bind to positively charged beads (ANION exchange<\/strong>). At a pH below the pI, the protein will be positively charged and bind to negatively charged beads (CATION exchange<\/strong>). After protein binding in low salt conditions, the column will be eluted in a gradient to high salt and each protein will elute at a characteristic salt concentration, allowing separation based on the net surface charges of the different proteins.<\/p>\n\n\n\n

There are 2 different types of ion exchangers: strong ion exchangers and weak ion exchangers. Strong ion exchangers do not display a variation in IEX capacity upon changes in the pH. They remain fully charged over a broad pH range and maintain their binding capacity both at high and low pH. Weak ion exchangers do show a variation in IEX capacity based upon changes in the pH. They take up or lose protons upon pH changes and can provide a different selectivity when a strong ion exchanger doesn\u2019t work for proper separation.<\/p>\n\n\n\n

ANION exchangers<\/strong><\/td><\/td>Functional group<\/strong><\/td><\/tr>
Quaternary ammonium (Q)<\/td>strong<\/td>-O-CH2<\/sub>N+<\/strong><\/sup>(CH3<\/sub>)3<\/sub><\/td><\/tr>
Diethylaminoethyl (DEAE)<\/td>weak<\/td>-O-CH2<\/sub>CH2<\/sub>N+<\/strong><\/sup>H(CH2<\/sub>CH3<\/sub>)3<\/sub><\/td><\/tr>
Diethylaminopropyl (ANX)<\/td>weak<\/td>-O-CH2<\/sub>CHOHCH2<\/sub>N+<\/strong><\/sup>H(CH2<\/sub>CH3<\/sub>)3<\/sub><\/td><\/tr>
CATION exchangers<\/strong><\/td><\/td>Functional group<\/strong><\/td><\/tr>
Sulfopropyl (SP)<\/td>strong<\/td>-O-CH2<\/sub>CHOHCH2<\/sub>OCH2<\/sub>CH2<\/sub>CH2<\/sub>SO3<\/sub>–<\/strong><\/sup><\/td><\/tr>
Methyl sulfonate (S)<\/td>strong<\/td>-O-CH2<\/sub>CHOHCH2<\/sub>OCH2<\/sub>CHOHCH2<\/sub>SO3<\/sub>–<\/strong><\/sup><\/td><\/tr>
Carboxymethyl (CM)<\/td>weak<\/td>-O-CH2<\/sub>COO–<\/strong><\/sup><\/td><\/tr><\/tbody><\/table>
Various ion exchange chromatography materials that can be used for anion or cation exchange chromatography.<\/figcaption><\/figure>\n\n<\/div>\n<\/div>\n\n\n
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