So now let's take a look at these three experiments. Let's begin with experiment number one. In experiment number one, he took that active ribonuclease enzyme that contains this secondary and tertiary structure and he placed it, he mixed it with an excess amount of Beter Mcaptoethanol and a large amount of urea. So eight molar concentration of urea. So what happened is the excess Beter mecaptoethanol broke down all those covalent disulfide bonds. So it broke down this bond, this bond, this bond and this bond, and the urea broke down the non covalent interactions that hold parts of the tertiary and the secondary structure together.