Cation-pi interactions: Difference between revisions
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Cationic moieties, such as sidechain nitrogens (lysine or arginine) or metal cations, that are within 6.0 Å of the face of an aromatic ring (phenylalanine, tyrosine, or tryptophan) may engage in polar interactions called cation-pi interactions (cation-π interactions). | Cationic moieties, such as sidechain nitrogens (lysine or arginine) or metal cations, that are within 6.0 Å of the face of an aromatic ring (phenylalanine, tyrosine, or tryptophan) may engage in polar interactions called cation-pi interactions (cation-π interactions). | ||
The flat face of an aromatic ring has a partial negative charge due to the [[#Chemistry|pi orbitals]. <!-- ([http://www.molphys.leidenuniv.nl/monos/smo/index.html?basics/photophysics.htm schematic], [http://www.webelements.com/shop/product.php/129/molyorbital_molecular_orbital_organic_structures_set physical model]). --> | The flat face of an aromatic ring has a partial negative charge due to the [[#Chemistry|pi orbitals]]. <!-- ([http://www.molphys.leidenuniv.nl/monos/smo/index.html?basics/photophysics.htm schematic], [http://www.webelements.com/shop/product.php/129/molyorbital_molecular_orbital_organic_structures_set physical model]). --> | ||
Cationic sidechains (Lys, Arg) or sometimes ligands (including metal ions) often align themselves centered over the faces of aromatic rings. Over one fourth of Trp's in the Protein Data Bank interact with cations, and 99% of significant cation-pi interactions occur within a distance of 6.0 Angstroms <ref name='GD'>PMID: 10449714</ref>. Cation-pi interactions make a significant contribution to the overall stability of most proteins. Gallivan and Dougherty (1999)<ref name='GD' /> concluded that "cation-pi interactions should be considered alongside the more conventional hydrogen bonds, salt bridges, and hydrophobic effects in any analysis of protein structure". They can also contribute significantly to intermolecular contacts and interactions with ligands. | Cationic sidechains (Lys, Arg) or sometimes ligands (including metal ions) often align themselves centered over the faces of aromatic rings. Over one fourth of Trp's in the Protein Data Bank interact with cations, and 99% of significant cation-pi interactions occur within a distance of 6.0 Angstroms <ref name='GD'>PMID: 10449714</ref>. Cation-pi interactions make a significant contribution to the overall stability of most proteins. Gallivan and Dougherty (1999)<ref name='GD' /> concluded that "cation-pi interactions should be considered alongside the more conventional hydrogen bonds, salt bridges, and hydrophobic effects in any analysis of protein structure". They can also contribute significantly to intermolecular contacts and interactions with ligands. | ||
*[http://firstglance.jmol.org First Glance in Jmol] finds and displays potential cation-pi interactions, as described [http://firstglance.jmol.org/notes.htm?#catpi here]. | *[http://firstglance.jmol.org First Glance in Jmol] finds and displays potential cation-pi interactions, as described [http://firstglance.jmol.org/notes.htm?#catpi here]. | ||