Zwitterion
From Wikipedia, the free encyclopedia
A zwitterion (from German "Zwitter" — "hybrid," "hermaphrodite") is a chemical compound that is electrically neutral but carries formal positive and negative charges on different atoms.<ref>IUPAC. , IUPAC Compendium of Chemical Terminology, Electronic Version. Retrieved November 12, 2006.</ref> Zwitterions are polar and usually have a high solubility in water and a poor solubility in most organic solvents.
Many molecules that contain both acidic and basic groups (and are therefore amphoteric) will exist as zwitterions at a certain pH. This pH is known as the molecule's isoelectric point. Such molecules make good buffer solutions — they resist change to the pH of a solution by selective ionisation. In the presence of acids, they will accept the hydrogen ions, removing them from the solution. In the presence of bases, they will donate hydrogen ions to the solution, again balancing the pH.
Typical examples of zwitterions are:
- Zwitterionic buffer compounds like HEPES, PIPES, CAPS, or MOPS.
- Natural products like the alkaloids psilocybin and lysergic acid.
- Zwitterionic detergents like CHAPSO.
- Amino acids such as glycine and alanine.
Less common examples of zwitterions are:
- quinonoid zwitterions.
- Drugs such as Fexofenadine (Allegra®).
[edit] References
<references/>ca:Zwitterió de:Zwitterion et:Kaksikioon eo:Ambaŭ-jono fr:Zwitterion id:Zwiter ion it:Zwitterione nl:Zwitterion pl:Jon obojnaczy fi:Kahtaisioni
