Protonophore
A protonophore, also known as a proton translocator, is an ionophore that moves protons across lipid bilayers. This would otherwise not occur as protons cations (H+) 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 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.[1][2] Both the neutral and the charged protonophore can diffuse across the lipid bilayer by passive diffusion and simultaneously facilitate proton transport.[3]
Representative protonophores include:
- 2,4-dinitrophenol
- Carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP)
- Carbonyl cyanide m-chlorophenyl hydrazone (CCCP)
Mechanism of action
The facilitated transport of protons across the biological membrane by protonophore is achieved as follows.[4]
- The anionic form of the protonophore (P−) is adsorbed onto one side (Positive) of the biological membrane.
- Protons (H+) from the aqueous solution combine with the anion (P−) to produce the neutral from (PH)
- PH diffuses across the biological membrane and dissociates into H+ and P− on the other side.
- This H+ is released from the biological membrane into the other aqueous solution
- 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
- ↑ http://biom.3322.org:2966/ebook1/biophy/Fundamental%20Principles%20of%20Membrane%20Biophysics.pdf (accessed 19th Nov 2008)
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