If you have a negatively charged ion-exchange column such as cm-cellulose and you are using it to isolate a particular protein, would you like the ph to be above or below that protein’s pi? why?

I would like to keep the pH below the isoelectric point or Pl

Explanation:

This is because i have a negtively charged ion change column and the negatively charged molecules of that ion exchange column will interract with target protein that is positively charged.

                        To keep a protein molecule in its positive charge i have to maintain its OH below the isoelctric point or Pl. Because at isoelectric point the protein will exist as zwitterion and above the isoelectric point the protein will exist as negatively charged.