Hey Tim,

You can include an anion exchange chromatography step in your purification process provided that your protein of interest remains as a cation in your purification buffer. Even if your protein act as a weak anion, it would be eluted at a lower ionic strength from a strong anion exchanger and nucleic acids would be eluted later at high ionic strength. But this entirely depends upon the isoelectric point of your protein and the pH of your buffer.

If you can bind your protein to an affinity resin on a column and then wash it with a buffer containing 1 M NaCl, you can remove all the nucleic acids. Those will flow through.

Dear Tim Lee

you can also add some endonucleases eg DNAse,, RNAse, or Benzoase during your lisys step.

Those enzimes will be removed during the purification and fragmented DNA is more easy purified or eliminated using ultrafiltratino of TFF during the protein concentration steps.

best regards

Manuele

Hello Tim Lee ,

in addition to all the advice given above, you can also try and change your lysis method. Harsh ones like sonication usually disrupt DNA in small fragments, and these are more likely to remain in the sample and attached to your protein.

When it comes to salt gradient to remove DNA, I would also add a wash (after your protein is eluted) at high salt, like 3M KCl, to clean out the column and remove all the DNA. DNA is very sticky, and can clog resins and cross-contaminate other samples.