SDS Page. Also known as SDS polyacrylamide gel electrophoresis. And the reason we use this setup is because it allows us to separate the two polypeptide chains based on their size and mass. So here we have the electrophoresis setup. We basically take the mixture of these two proteins, we put them inside the well and we wait some time. And what will happen is, because this has a greater size, it will experience a greater resistance as it travels down to the bottom of our gel.