Applications
Calixarenes are applied in enzyme mimetics, ion sensitive electrodes or sensors, selective membranes, non-linear optics and in HPLC stationary phases. In addition, in nanotechnology calixarenes are used as negative resist for high-resolution electron beam lithography .
A tetrathiaarene is found to mimic aquaporin proteins. This calixarene adopts a 1,3-alternate conformation (methoxy groups populate the lower ring) and water is not contained in the basket but grabbed by two opposing tert-butyl groups on the outer rim in a pincer. The nonporous and hydrophobic crystals are soaked in water for 8 hours in which time the calixarene:water ratio nevertheless acquires the value of one.
Calixarenes are able to accelerate reactions taking place inside the concavity by a combination of local concentration effect and polar stabilization of the transition state. An extended resorcinarene cavitand is found to accelerate the reaction rate of a Menshutkin reaction between quinuclidine and butylbromide by a factor of 1600.
In heterocalixarenes the phenolic units are replaced by heterocycles, for instance by furans in calixfuranes and by pyridines in calixpyridines. Calixarenes have been used as the macrocycle portion of a rotaxane and two calixarene molecules covalently joined together by the lower rims form carcerands.
Calixarene was used as scaffold to assemble a construct bearing four Tn-antigen unit, at upper rim, and the immunoadjuvant P3CS, at lower rim. The construct showed a cluster effect in the production of Tn specific IgG antibodies in mice when compared to an analogous monovalent construct. This reveals perspectives for potential applications in cancer immunotherapy.
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