0A73DFF9d01 - E ARTICLES Cation-m...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: E ARTICLES Cation-m InteractionsinChemistryandBiology: A NewViewofBenzene,Phe,Tyr, andTrp DennisA.Dougherty CationsbindtotheTrfaceofan aromaticstructurethroughasurprisinglystrong,non- covalentforcetermedthecation-Trinteraction.Themagnitudeandgeneralityoftheeffect havebeenestablishedbygas-phasemeasurements and bystudiesofmodel receptors inaqueous media. To firstorder, the interaction can be considered an electrostatic attractionbetweenapositivechargeandthequadrupolemomentofthearomatic.Agreat deal ofdirectand circumstantial evidence indicatesthatcation-Trinteractionsareim- portantinavarietyofproteinsthatbindcationicligandsorsubstrates.Inthiscontext,the amino acidsphenylalanine(Phe),tyrosine(Tyr),and tryptophan (Trp)can beviewed as polar,yethydrophobic, residues. NoncovalentintermolecuLlarforcesplaya majorroleindeterminingthestructuresof biological macromoleculesand inmediat- ingprocessessuchasreceptor-ligandinter- actions,enzyme-substratebinding,andan- tigen-antibody recognition. Although the hydrophobiceffect,hydrogenbonding,and ionpair(saltbridge)interactionshavebeen extensivelystudiedand discussed,thereis another important butgenerally underap- preciatednoncovalent bindingforce.Cat- ions, from simple ions like Li' to more complex organic structureslikeacetylcho- line(ACh),arestronglyattractedtothe ar faceofbenzene and otheraromaticstruc- tures(Fig. 1).Several featuresdistinguish this cation-ITinteraction fromothernon- covalent bindingforcesand make itespe- ciallywellsuitedtonoveltypesofbiological binding. Anoverviewofresearcheffortsfrommy labsand many other groups ispresented herethatdelineatesthescopeand impor- tanceof cation-ITinteractions. Fundamen- talgas-phaseionstudieshaveledtoamodel forthe physical origin ofthe effect and suggestanewwayof lookingatbenzeneand otheraromaticsystems. Studiesoforganic modelsystems, coupledwithawiderangeof resultsfromstructural biology,haveestab- lishedthe relevance of cation-Tr interac- tionsto biologicalrecognitionthroughin- teractionswith aromatic sidechainsfrom theaminoacids Phe,Tyr,andTrp. Mostimportant,notonlycanabinding sitemadeupofaromaticrings bindcations, italsocancompetewiththehighlyfavor- able solvation ofan ion provided by an aqueousmedium. Hence, binding sitescan becreatedthatareinonesensepolar(in that theyareableto bind ions) yet are overall hydrophobic (being composed of hydrocarbon units). This combination of TheauthorisintheDivisionofChemistryandChemical Engineering,CaliforniaInstituteofTechnology, Pasade- na,CA 91125,USA.E-mail:dad@igor.caltech.edu properties isespeciallywell suited tothe interiorofaproteinoracellmembrane, environments inwhich cationbindingby conventionalionpairingmaynotbefeasi- ble.To document such behavior, Ibriefly describeanumberofbiologicalstructuresin whichcation-Irinteractionsareknown to be important. Itisnot my intention to present an exhaustive listofallpossible cation-ITinteractions,butrathertodescribe somerepresentative examplesthatillustrate this phenomenon....
View Full Document

This note was uploaded on 05/28/2010 for the course WE BIBI010000 taught by Professor Marnikvuylsteke during the Spring '10 term at Ghent University.

Page1 / 6

0A73DFF9d01 - E ARTICLES Cation-m...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online