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Process Design Considerations for Large–Scale Chromatography of Biomolecules
Published in Kenneth E. Avis, Vincent L. Wu, Biotechnology and Biopharmaceutical Manufacturing, Processing, and Preservation, 2020
Richard Wisniewski, Egisto Boschetti, Alois Jungbauer
Sulfates are, in most cases, attached to polysaccharide sorbents and are typically used at pH below 7. Sulfonates are attached to both saccharidic polymer material and synthetic polymers. Carboxylates are obtained by alkaline reaction of chloroacetic acid on hydroxyl-containing polymers; they are widely used as cation exchangers in a more restricted range of pH than sulfonated media. Quaternary amino groups are well-known structures for strong cationic media; their high pK value allows their use in a wide pH range with, in a number of cases, the provision of higher selectivity in separating anionic proteins than media with tertiary amino groups. Diethyl-aminoethyl (DEAE) groups, very popular in protein separations, are complex structures resulting from the reaction between diethyl-aminoethyl chloride and a nonionic sorbent containing hydroxyl groups under alkaline conditions. Such chemical conditions induce secondary reactions on the monomer itself, generating oligo-DEAE chains. These complex structures with different pKs are characterized easily by titration curves; however, they do not modify the ion-exchange mechanism with proteins. In contrast to gel filtration media (see below), the matrix does not have a strictly defined pore size. Here the pores are generally large enough to avoid any possible molecular sieving effect during separation. Commercially available ion exchangers have various mechanical and chemical resistances and are based on natural, synthetic, and mineral composite materials. The type of group immobilized to the matrix determines the type and strength of the ion exchanger. There are a variety of groups that have been selected for use as ion exchangers (Table 3.6).
Soluble expression, rapid purification, biological identification of chicken interferon-alpha using a thioredoxin fusion system in E. coli and its antiviral effects to H9N2 avian influenza virus
Published in Preparative Biochemistry and Biotechnology, 2019
Jun Zhao, Hai-Yang Yu, Yu Zhao, Feng-Hua Li, Wei Zhou, Bin-Bin Xia, Zhi-Yuan He, Jason Chen, Guo-Tuo Jiang, Ming-Li Wang
Anion-exchange chromatography is a process that separates substances based on their charges using an ion-exchange resin containing positively charged groups, such as diethyl-aminoethyl groups (DEAE). In solution, the resin is coated with positively charged counter-ions (cations). Anion exchange resins will bind to negatively charged molecules, displacing the counterion. Anion exchange chromatography is commonly used to purify proteins, amino acids, sugars/carbohydrates and other acidic substances with a negative charge at higher pH levels.