So he used urea and betama capto ethanol. Now, urea is basically used to break down the non covalent bonds, such as hydrogen bonds and ionic bonds that hold together that secondary structure of the protein as well as parts of the tertiary structure. And he used bader mercaptoethanol to basically break down the covalent bonds, the disulfide bonds that exist and hold that tertiary structure of the protein together. So Beter Mcappto ethanol uses an oxidation reduction reaction. So this itself is oxidized and reduces the disulfide bonds. It breaks them down.