And as the H ion is being pulled away onto the nitrogen, as shown in this particular diagram, these two electrons in the sigma bond move closer to the sulfur atom, and that increases the electron density, the electron cloud around the sulfur, and that increases its ability to act as a nucleophile. So as the H atom is being pulled away onto the nitrogen of the nearby histidine residue, we see that these two electrons move closer to the sulfur and the electron density on the sulfur increases. And so as we have this incoming substrate molecule these two electrons attack nucleophilically the carbon on the carbonyl and that displays the pi bond. And so once the step takes place twice we form the same type of tetrahedral intermediate that we formed in the serene protease reaction mechanism. And just like in Seren proteases we can have an oxyanion hole that stabilizes the negative charge on that oxygen. Once we form the tetrahedral intermediate in cysteine proteases we can also have a similar type of oxygenine hole that stabilizes that relatively unstable and high energy tetrahedral intermediate.