Cation-pi interactions: Difference between revisions
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==Chemistry== | ==Chemistry== | ||
<table align="right"><tr><td>[[Image:Benzene Orbitals.png|400 px]]</td></tr><tr><td></td></tr></table> | <table align="right"><tr><td>[[Image:Benzene Orbitals.png|400 px]]</td></tr><tr><td></td></tr></table> | ||
Six-carbon aromatic rings occur in the sidechains of 3 of the [[amino acids|20 standard amino acids]]: namely [[Amino_Acids#Phenylalanine|phenylalanine]], [[Amino_Acids#Tryptophan|tryptophan]], and [[Amino_Acids#Tyrosine|tyrosine]]. The atomic p orbitals of the carbons overlap sideways, forming a pi (π) orbital system, or pi cloud of delocalized electrons<ref name="lillya">[[User:Eric Martz|Eric Martz]] thanks [http://www.cns.umass.edu/faculty/directory/c-peter-lillya Peter Lillya] for help with terminology.</ref>. | Six-carbon aromatic rings occur in the sidechains of 3 of the [[amino acids|20 standard amino acids]]: namely [[Amino_Acids#Phenylalanine|phenylalanine]], [[Amino_Acids#Tryptophan|tryptophan]], and [[Amino_Acids#Tyrosine|tyrosine]]. The atomic p orbitals of the carbons overlap sideways, forming a pi (π) orbital system, or pi cloud of delocalized electrons<ref name="lillya">[[User:Eric Martz|Eric Martz]] thanks [http://www.cns.umass.edu/faculty/directory/c-peter-lillya Peter Lillya] for help with terminology.</ref>. The pi clouds on each face of the ring have a partial negative charge, while the edge of the ring has a compensating partial positive charge. The approach of a positive charge to one face of the ring induces further polarization, and in the proper conformation produces an electrostatic interaction called a '''cation-pi interaction'''. | ||
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