Protonophore

A protonophore, also known as a proton translocator, is an ionophore that allows protons to cross lipid bilayers. This would otherwise not occur as protons have positive charge and hydrophilic properties, making them unable to cross without a channel or transporter. Protonophores are generally aromatic compounds 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 in the molecule.[1][2] Both the neutral and the charged species can diffuse across the lipid bilayer by passive diffusion and simultaneously facilitating proton transport.[3]

Representative protonophores include:

Mechanism of action

The facilitated transport of protons across the biological membrane by protonophore is achieved as follows.[4]

  1. The anionic form of the protonophore (P−) is adsorbed onto one side (Positive) of the biological membrane.
  2. Protons (H+) from the aqueous solution combine with the anion (P−) to produce the neutral from (PH)
  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 (its electrostatic attraction to the positive side of the membrane).

See also

References

  1. ↑ http://biom.3322.org:2966/ebook1/biophy/Fundamental%20Principles%20of%20Membrane%20Biophysics.pdf (accessed 19th Nov 2008)
  2. ↑ Nicholls, David G., and Ferguson, Stuart J. (2002). "Bioenergetics 3". Academic Press, London. ISBN 0-12-518121-3.
  3. ↑ Chopineaux-Courtois V, Reymond F, Bouchard G,Carrupt PA, Testa B, Girault HH. (February 1999). "Effects of Charge and Intramolecular Structure on the Lipophilicity of Nitrophenols". J. Am. Chem. Soc. 121 (8): 1743–1747. doi:10.1021/ja9836139.
  4. ↑ Ozaki S, Kano K, Shirai O (August 2008). "Electrochemical elucidation on the mechanism of uncoupling caused by hydrophobic weak acids". Phys Chem Chem Phys 10 (30): 4449–55. doi:10.1039/b803458c. PMID 18654685.