Techniques for the separation of proteins by isoelectric point column chromatography

The common protein streptavidin, and the n-type glycoproteins ovalbumin and transferrin were eluted at their respective isoelectric points from CM-Sephadex, CM-Sepharose, SP-Sephadex, and SP-Sepharose by0.1 M Tris succinate buffer. No tailing occurred with a linear gradient where the ionic strength was gradually de- creased. Although streptavidin and a large proportion of ovalbumin were not absorbed by CM-Sephadex equili- brated with a0.2M buffer, transferrin and some of the ovalbumin were eluted at their isoelectric points. This method should be called isoelectric point column chromatography because compounds are eluted from the column at their isoelectric points. This method may be suitable for use with various proteins. In particular, glycoproteins, which are considered to be difficult to purify, can be easily eluted at their isoelectric points under high ionic strength.