While the ones have equal amounts, they have a net neutral charge. And those that have more negatively charged side chains, those have a net negative charge. Now, because certain proteins differ from one another based on their net charge, this is another property that we can use to separate and purify proteins. And the technique, the method that we use to separate proteins based on the net charge is called ion exchange chromatography, or simply ion chromatography. So the setup in ion exchange chromatography is very similar to that of gel filtration chromatography. So it looks something like this.