„Ziel erreicht.“ Oder: „Bitte wenden.“ Ein normatives Modell zur Bewertung der Transformationsprozesse in Mittel- und Osteuropa

Cation sitting in aromatic cages: ab initio computational studies on tetramethylammonium–(benzene)n (n=3–4) complexes

“…9,10 Meanwhile, protein crystal structures demonstrate that a cation is capable of binding with 3 or 4 aromatic residues. [11][12][13][14][15][16][17][18][19][20] For example, there are three tryptophan residues in the X-ray structure of the periplasmic ligand binding protein ProX (PDB code 1R9L) 11 interacting simultaneously with the positively charged quaternary amine of the ligand glycine betaine via three of the indole groups of the residues. Similar cation-p interaction between a cation and three aromatic residues, has also been found in the X-ray structure of a choline-binding domain in LytA (PDB code 1HCX).…”

“…[14][15][16][17] Electrophysiological data suggest that the mechanism of blocking of the channel by quaternary ammonium moieties involves the interaction of the cationic moieties with the four phenol groups. [18][19][20] All these structural and functional data show a fact that a single cation can interact with one, two, three, or as many as four aromatic rings. In other words, a cation may stably sit in a cage composed of several aromatic systems.…”