And this leads us directly into reason number two. As a result of this modified negatively charged groove found on this residue, because of this negative charge, that essentially gives this modified residue a high potential to form hydrogen bonds. And so the negatively charged oxygen atoms of the phosphorylated side chain residue can form hydrogen bonds with other molecules, for instance, the target enzyme or the target substrate molecule. And so this can increase the specificity of the interaction between the active side of the enzyme and that substrate molecule. Now number three is the protein kinases are actually able to easily adjust the rates, the kinetics of this reaction. So depending on the physiological needs of the cells, this reaction can take place very, very quickly in a matter of seconds or it can take place over a very long period of time.