An enzyme may be reversibly or irreversibly bioactivated. Donepezil binds and reversibly inactivates the cholinesterases, thus inhibiting hydrolysis of acetylcholine. It selectively and reversibly blocks DNA replication in susceptible bacteria. Another agent, textilinin, is a Kunitz-like serine protease inhibitor that selectively and reversibly inhibits plasmin. These insecticides kill insects by reversibly inactivating the enzyme acetylcholinesterase. It reversibly inhibits NMDAR-mediated ion currents. Thermodynamic processes can be carried out in one of two ways&colon; reversibly or irreversibly. Hemoglobin contains four heme groups each capable of reversibly binding to one oxygen molecule. Dapsone arrests myeloperoxidase in an inactive intermediate form, reversibly inhibiting the enzyme. An ionophore is a chemical species that reversibly binds ions. Saxitoxin binds reversibly to the sodium channel. Naproxen works by reversibly inhibiting both the COX-1 and COX-2 enzymes as a non-selective coxib. Transferrin glycoproteins bind iron tightly, but reversibly. In the system and reversibly bind together to form dimers. The thiol-based polymers have disulfide bonds that can be reversibly cross-linked through oxidation and reduction.