In the first step of the trypsin mechanism, the side-chain oxygen of Ser 195 attacks the carbonyl carbon of the substrate. Use PyMOL and your model of the enzyme substrate complex to determine the distance between these two atoms. How much motion (in Angstroms) of the substrate or enzyme do you think there would have to be to form the tetrahedral transition rate ? Hint : how close together are the atoms in a typical oxygen-carbon single bond?