And once inside, they essentially react in a covalent manner. They modify the residues found inside the active side in a covalent manner and that inhibits that enzyme's activity. Now, what's one example of an affinity label? Well, when we'll discuss the process of glycolysis, we'll see that an intermediate molecule in glycolysis is known as dihydroxy acetone phosphate. And what happens in glycolysis is dihydroxy acetone phosphate is transformed into another isomer by an enzyme we call triosphosphate isomerase. Now, inside the active side of triosphosphate isomerase, we have this glutamate molecule.