After a long and difficult semester of research, you have nearly purified your protein of interest (YPOI), but Coomassie stained gel electrophoresis shows that there are three remaining proteins (contaminanting proteins). From mass spectrometric analysis of each band from the gel, you learn the size and isoelectric point for each of the contaminating proteins as well as your protein, YPOI, as follows:

Protein Molecular Weight (Daltons) Isoelectric point (pI)
YPOI 35,000 7.9
Contaminant 1 32,000 6.0
Contaminant 2 89,500 5.9
Contaminant 3 110,000 8.9

You have three types of column chromatography resins available to separate YPOI from the three contaminants.
- G100: Gel filtration resin (with a fractionation range of 20,000 to 100,000 daltons)
- DEAE cellulose: a positively charged ion exchange resin
- CMC cellulose: a negatively charged ion exchange resin

Your proteins must be in a buffered solution at pH 7.0 to ensure that YPOI remains stable.