DNA removal in target molecule purification

A method of removing genomic DNA from a cell culture biological sample or culture supernatant biological sample comprising a protein target molecule and positively charged complexes comprising genomic DNA, the method comprising,

• contacting the cell culture biological sample or culture supernatant biological sample to a cation exchange ligand comprising as a charged substituent a sulfonic acid or phosphoric acid moiety, said ligand bound to a solid support or bound to a soluble polymer under conditions such that:
• (a) positively charged genomic complexes comprising DNA from the sample bind the cation exchange ligand;
• and
• (b) non-binding components of the sample, including the protein target molecule, do not substantially bind to the cation exchange ligand, the solid support, or the soluble polymer;
• separating the non-binding components of the sample, including the target molecule, from the positively-charged complexes bound to the cation exchange ligand to produce a purified sample having a reduced amount of genomic DNA;
• and
• performing at least one more protein target molecule purification step on the purified sample having a reduced amount of genomic DNA,
• wherein the protein target does not bind the cation exchange ligand from the contacting through the separating.