Experimental evidence for the functional relevance of anion-pi interactions.
Attractive in theory and confirmed to exist, anion-pi interactions have never really been seen at work. To catch them in action, we prepared a collection of monomeric, cyclic and rod-shaped naphthalenediimide transporters. Their ability to exert anion-pi interactions was demonstrated by electrospray tandem mass spectrometry in combination with theoretical calculations. To relate this structural evidence to transport activity in bilayer membranes, affinity and selectivity sequences were recorded. pi-acidification and active-site decrowding increased binding, transport and chloride > bromide > iodide selectivity, and supramolecular organization inverted acetate > nitrate to nitrate > acetate selectivity. We conclude that anion-pi interactions on monomeric surfaces are ideal for chloride recognition, whereas their supramolecular enhancement by pi,pi-interactions appears perfect to target nitrate. Chloride transporters are relevant to treat channelopathies, and nitrate sensors to monitor cellular signaling and cardiovascular diseases. A big impact on organocatalysis can be expected from the stabilization of anionic transition states on chiral pi-acidic surfaces.
Dawson
Ryan E
RE
Department of Organic Chemistry, University of Geneva, Geneva, Switzerland.
Hennig
Andreas
A
Weimann
Dominik P
DP
Emery
Daniel
D
Ravikumar
Velayutham
V
Montenegro
Javier
J
Takeuchi
Toshihide
T
Gabutti
Sandro
S
Mayor
Marcel
M
Mareda
Jiri
J
Schalley
Christoph A
CA
Matile
Stefan
S
D000838:Anions / Q000737:chemistry*; D007094:Imides / Q000737:chemistry; D017136:Ion Transport; D008051:Lipid Bilayers / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D009281:Naphthalenes / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
D000838:Anions; D007094:Imides; D008051:Lipid Bilayers; D009281:Naphthalenes; C542131:naphthalenediimide