And this is the same Irreversible inhibitor that we spoke about in our lecture on Irreversible inhibitors. So if we take DIPF and we mix it with an enzyme and inside the active site, we have a Serene molecule. And if the reactivity of that serine molecule is quite high, then that DIPF will basically form a covalent bond with that oxygen of the Serene displacing, the H, and that will kick off this fluoride atom and we form a covalent bond between the oxygen and the phosphorus atom. And once we create this covalent modification, the Irreversible inhibitor basically blocks the activity of that enzyme. And so we know that because the activity of the enzyme is inhibited, that means that the DIPF must be bound to a Serene found inside the active site. Now, out of all the 28 Serene amino acids that we find in China Trypsin, this is the only serine that reacts with DIPF.