Liquid membrane transport of cytochrome c using a calix[6]arene carboxylic acid derivative as a carrier

Calixarene-mediated liquid membrane transport of choline conjugates 3: The effect of handle variation on neurotransmitter transport

Upper rim phosphonic acid functionalized calix[4]arene affects selective transport of multiple molecular payloads through a liquid membrane. The secret is in the attachment of a receptor-complementary handle to the payload. We find that the trimethylammonium ethylene group present in choline is one of several general handles for the transport of drug and drug-like species. Herein we compare the effect of handle variation against the transport of serotonin and dopamine. We find that several ionizable amine termini handles are sufficient for transport and identify two ideal candidates. Their performance is significantly enhanced in HEPES buffered solutions. This inquiry completes a series of 3 studies aimed at optimization of this strategy. In completion a new approach towards synthetic receptor mediated selective small molecule transport has emerged; future work in vesicular and cellular systems will follow.

Calixarene-Mediated Liquid-Membrane Transport of Choline Conjugates

A series of supramolecular calixarenes efficiently transport distinct molecular species through a liquid membrane when attached to a receptor-complementary choline handle. Calix-[6]arene hexacarboxylic acid was highly effective at transporting different target molecules against a pH gradient. Both carboxylic- and phosphonic-acid-functionalized calix[4]arenes effect transport without requiring a pH or ion gradient. NMR binding studies, two-phase solvent extraction, and three-phase transport experiments reveal the necessary and subtle parameters to effect the transport of molecules attached to a choline "handle". On the other hand, rescorin[4]arene cavitands, which have similar guest recognition profiles, did not transport guest molecules. These developments reveal new approaches towards attempting synthetic-receptor-mediated selective small-molecule transport in vesicular and cellular systems.

Protein surface recognition by calixarenes

The present review summarizes recently developed calixarene derivatives for protein surface recognition which are able to identify, inhibit, and separate specific proteins.

Dominant structural factors for complexation and denaturation of proteins using carboxylic acid receptors

Complexation accompanied by denaturation of protein with synthetic carboxylic acid receptors was investigated, to evaluate the key factors for recognition of proteins. The synthetic receptors used were tetraphenylporphyrin (TPP) derivatives and receptors bearing multiple (2-8) carboxylic acid groups. The complexation behavior was quantified from the absorption in the far UV CD spectrum attributed to the secondary structure of the protein. TPP derivatives bearing multiple carboxylic acid groups in the side chains exhibited higher affinity than other receptors that were smaller and had fewer carboxylic acid groups. As the degree of complexation was influenced by the pH and ionic strength in aqueous solution, electrostatic interaction was one of the most important factors for the recognition of proteins. Complexation was also estimated by observation of fluorescence quenching of the TPP derivatives. The stoichiometry of the complexes between lysozyme and the porphyrins was investigated by quantitative analysis of the denaturation using CD spectra. From the results of Job plots and slope analysis for the amount of denatured protein, formation of 1:1 complexes was confirmed. The equilibrium association constants (K(ass)) for lysozyme and the TPP receptors ranged from 0.6×10(6) to 1.1×10(6)M(-1). The lytic activity of lysozyme was partially lost in the presence of anionic TPP derivatives, due to complexation and denaturation.