We moved on to gel filtration chromatography, in which we separate the protein mixture based on their size. And finally, we discussed ion exchange chromatography, in which we separate the proteins based on their net charge. Now we're going to discuss a fifth method by which we can purify our protein mixture. And in this method, we also use a specific property of proteins. So many proteins inside our body have a specific high affinity to some type of molecule. And the general example of these proteins are enzymes.