Bio-Rad Aurum Ion Exchange Mini Kits - Manual (Page 3)

Section 1
Introduction
Proteomics Sample Fractionation
Sample preparation plays an ever-increasing role in proteomics research.
Selective separation techniques prior to multidimensional analysis, such as 2-D
gel electrophoresis, HPLC-MS, or HPLC-CE, can significantly improve the
chances of resolving complex protein mixtures into their individual proteins.
Among these techniques are anion exchange (AEX) and cation exchange
(CEX) chromatography. Aurum AEX and CEX columns allow rapid fractionation
of complex protein mixtures in only a few steps using the common technique
of ion exchange chromatography.
Ion Exchange Chromatography
Ion exchange chromatography can be used to concentrate and purify proteins
based on their ionic charge or isoelectric point (pI) at a given pH. At the
isoelectric point of a protein, its net charge is zero. At a pH higher than the pI
of the protein, the protein will be negatively charged and will bind to an AEX
resin. At a pH lower than the pI, the protein will be positively charged and will
bind to a CEX resin. When an ion is applied to an ion exchanger of opposite
charge, it is adsorbed to the resin, while neutral ions or ions of the same
charge are eluted in the flow-through fraction. Binding of the ions is reversible,
and adsorbed molecules are commonly eluted with salt or a change of pH.
Table 1. Choosing the appropriate column.
Resin Type Protein of Interest
AEX Acidic
CEX Basic
The choice of whether to use an anion or cation exchanger is determined
mainly by the pI, and the relationship between pH and the activity or stability of
the protein of interest. Once the type of ion exchanger is determined, the
choice of buffer and pH is also determined by the relationship between pH
and activity.
Resins and Buffers Description
Each Aurum AEX and CEX column contains 0.2 ml of UNOsphere ™ Q or S
support, unique media based on a proprietary polymerization process. Both
the UNOsphere Q and S ion exchange media were developed to deliver
efficient protein capture and high binding capacity. The Aurum AEX and CEX
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