Sense of isoelectric focusing of protein-fraction from ion exchange chromatograp - (May/08/2008 )

Another question,
I do anion exchange chromatography to purify some proteins. I find one protein of my interest in one fraction. Then after AEC, I want to do at least one additional step of purification, for example reverse phase chromatography (RPC) and then analysis of all RPC fractions by western blot. But as another option I was also thinking about performing 2D gel of the relevant fraction from AEC.
However both ion exchange chromatography and isoeletric focusing are on principle based on the separation of proteins according their charge. Therefore, does it have any sense to do 2D gel (or just isoelectric focusing) of sample already pre-purified by ion exchange chromatography -does it increase purity of any protein?

Thanks in advance for you suggestions,
vic

2d may work to your advantage because you include a size separation component.

in fact, when purifying proteins by classical lc methods, the final step is often gel filtration (size separation) polishing.

ief alone may allow some separation. even though the charges on the proteins in the same fraction from iec are similar, there may still be enough difference in pI to separate by ief.