Now, this is the other example. And in this particular case, we see that di isopropyl phosphoridate actually reacts with serene amino acids. For instance, we know that in the active side of acetylcholinesterase, we have these serine amino acids that catalyze the reactions. And so, if we mix this active side, so an enzyme that contains an active side with a serene, then this diesopropyl. Phosphorfluoridate will essentially form a covalent bond between this phosphor and this oxygen and that will kick off the f, the fluoride and also that H to form the following Covalent modification. And so these are two examples of group specific irreversible inhibitors.