Rational design of biologically important chemosensors: A novel receptor for selective recognition of acetylcholine over ammonium cations

[GRAPHICS] In consideration of competition between cation-pi and hydrogen bond interaction forces, we designed a novel receptor, 1,3,5-tris(pyrrolyl)benzene, which shows high selectivity for acetylcholine (ACh). The selectivity of the receptor for ACh over other ammonium cations is. demonstrated by the ion-selective electrode (ISE) method in buffer solution. The binding free energy of the receptor with ACh in chloroform solution is measured to be 3.65 kcal/mol in the presence of chloride anion by nuclear magnetic resonance spectroscopy, and that in water is estimated to be much greater (similar to6 kcal/mol).