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. So at the end, we basically formed the following denatured enzyme, the enzyme that if not in its active form. Now, what he did next was by using a semipermeable membrane, he removed these two agents at the same exact time. So he isolated this denatured enzyme by removing these two agents at the same time.