Recognition of Steroids by Self-assembled Monolayers of Calix[4]arene-Resorcin[4]arene Receptors

摘要

Calix [4] arene-resorcin [4]-arene (2:1) receptor adsorbate 2 equipped with four didecyl sulfide groups self-assembles in monolayers (SAMs) on gold. These monolayers were characterized by contact angle measurements, polarized infrared external reflectance spectroscopy (PIERS), electrochemical capacitance and resistance measurements, and X-ray photoelectron spectroscopy (XPS). Interactions of a monolayer of 2 with steroid guests were investigated by surface plasmon resonance (SPR) spectroscopy. The results show that steroids interact more strongly with a monolayer of 2 than with a hydrophobic reference monolayer of octadecanethiol. There is virtually no detectable interaction with a hydrophilic reference monolayer of 11-mercaptoun-decan-1-ol. Mixed monolayers of 2/11-mercaptoundecan-1-ol and of 2/decanethiol showed lower SPR responses with the steroids than the pure monolayer of 2. Concentration-dependent experiments with prednisolone-21-acetate, corticosterone-21-acetate, and cortisone-21-acetate on the mixed monolayer showed Langmuir-type adsorption with affinity constants between 2.0 * 10~5 and 3.5 * 10~5M~(-1).