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What is ion exchange chromatography?
Ion exchange chromatography (IEX) is a form of adsorption chromatography, which separates molecules on the basis of charge.
IEX is one of the most widely used chromatography techniques for the purification of proteins. However, it also lends itself itself to the separation of peptides and oligonucleotides.
IEX is useful at all stages of a purification scheme and is eluted either by step elution or gradients.
The load capacity of step-eluted IEX is very high, which makes it excellent as a capture step as well as for concentrating samples in general.
The high resolution obtainable makes IEX very useful also for intermediate purification and for polishing.
Results can be controlled in a predictable way by controlling running pH, salt concentration, and by selecting the type of ion exchanger.
When run within the stability window for the sample molecules, recoveries achieved are normally better than 80-90%.
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Fig 1. Basis for selectivity in IEX -
Charged amino acids on the surface of a protein can bind to
oppositely charged ligands of the ion exchanger.
Arrows indicate some charged regions of lysozyme. |
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