Selective Purification of a Bacterial Protein by Negative Ion-Exchange Chromatography

Begin with an ion-exchange resin solution containing positively charged functional groups for selective protein binding.

Next, take a protein extract obtained from host bacterial cells engineered to overexpress a virulence factor from the pathogenic bacterium Helicobacter pylori.

The extract contains the target virulence factor along with host-cell proteins in a buffer at pH 8.

Mix the protein extract with the resin and incubate with agitation to ensure uniform protein-resin interaction.

Host proteins, having isoelectric points lower than the buffer pH, become negatively charged and bind to the positively charged resin.

The target protein, with an isoelectric point close to the buffer pH, remains largely uncharged and stays unbound.

Transfer the protein–resin slurry into a chromatography column and allow the resin to settle.

Collect the liquid phase containing the unbound target protein.

Rinse the resin with the buffer to ensure maximal recovery of the target protein.

To prepare 15 milliliters of DEAE resin, suspend 0.6 grams of DEAE resin dry powder in 30 milliliters of Tris-HCl buffer at room temperature for at least one day.

Centrifuge the resin at 10,000 times g at four degrees Celsius f