posted on 2006-01-06, 00:00authored byJeongryul Kim, Balamurali Raman, Kyo Han Ahn
The recognition of dopamine in water has been achieved with tripodal oxazoline-based artificial receptors,
capable of providing a preorganized hydrophobic environment by rational design, which mimics a hydrophobic pocket predicted for a human D2 receptor. The receptors show an amphiphilic nature owing
to the presence of hydrophilic sulfonate groups at the periphery of the tripodal oxazoline ligands, which
seems to contribute in forming the preorganized hydrophobic environment. The artificial receptors
recognized dopamine hydrochloride in water with reasonable selectivity among various organoammonium
guests examined. The observed binding behavior of the receptors was explained by evoking guest inclusion
in the preorganized hydrophobic pocket-like environment and not by simple ion-pairing interactions.
The rationally predicted 1:1 inclusion binding mode was supported by binding studies such as with a reference receptor that cannot provide a similar binding pocket, Job and VT-NMR experiments, electrospray
ionization mass analysis, and guest selectivity data. This study implies that an effective hydrophobic environment can be generated even from an acyclic, small molecular artificial receptor. Such a preorganized
hydrophobic environment, as being utilized in biological systems, can be effectively used as a complementary binding force for the recognition of organoammonium guests such as dopamine hydrochloride
in water.