Protonophore


A protonophore, also known as a proton translocator, is an ionophore that moves protons across lipid bilayers or other type of membranes. This would otherwise not occur as protons cations have positive charge and hydrophilic properties, making them unable to cross without a channel or transporter in the form of a protonophore. Protonophores are generally aromatic compounds with a negative charge, that are both hydrophobic and capable of distributing the negative charge over a number of atoms by π-orbitals which delocalize a proton's charge when it attaches to the molecule. Both the neutral and the charged protonophore can diffuse across the lipid bilayer by passive diffusion and simultaneously facilitate proton transport. Protonophores uncouple oxidative phosphorylation via a decrease in the membrane potential of the inner membrane of mitochondria. They stimulate mitochondria respiration and heat production. Protonophores are often used in biochemistry research to help explore the bioenergetics of chemiosmotic and other membrane transport processes. It has been reported that the protonophore has antibacterial activity by perturbing bacterial proton motive force.
Representative anionic protonophores include:
Representative cationic protonophores include:
Representative zwitterionic protonophores include:
The facilitated transport of protons across the biological membrane by anionic protonophore is achieved as follows.
  1. The anionic form of the protonophore is adsorbed onto one side of the biological membrane.
  2. Protons from the aqueous solution combine with the anion to produce the neutral form
  3. PH diffuses across the biological membrane and dissociates into H+ and P− on the other side.
  4. This H+ is released from the biological membrane into the other aqueous solution
  5. P− returns to the first side of the biological membrane by electrophoresis.