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Wednesday, July 10, 2013

DEAE Cellulose Column for Protein Purification

DEAE - Diethyl Amino Ethyl Cellulose columns are used for Protein purification. DEAE cellulose is an anionic resin which can be used to bind -vely charged proteins.

Proteins can be eluted by altering either by increasing the salt concentration or by altering the pH.

Structure of DEAE

DEAE is a weak ion exchange resin, which means the pH range at which it can be used is limited, charge density will vary.

The diethylamino group (-CH2-CH2-NH+-CH2-CH3) of DEAE-cellulose carries a positive charge which is responsible for the ion-binding properties of this resin. Effectively, negatively charged
amino acids/proteins will interact with the diethylamino group (via electrostatic interactions), while positively charged amino acids/proteins will be eluted. Since the diethylamino group has a pKa close to 8.5, it will be deprotonated at pH values above 8.5 and will lose all ability to bind negatively charged molecules.

Protonation is the addition of a proton H+ to an atom. In this case protonation results in net positive charge.

Deprotonation is the loss of a proton H+ from an atom, in this case deprotonation results in the loss of postive charge from the DEAE and there by it loses its ability to bind -vely charged proteins when the pH is raised above 8.5.