Hydrophobic Gaps of Steroid Size in a Surface Monolayer Collect 1,2-trans-Cyclohexanediol and Glucose from Bulk Water

Abstract

Mixed monolayers made of steroid thiol molecules lying flat on the surface and thin octadecanethiol walls have been prepared on gold by subsequent chemisorption and self-assembly procedures. Cyclovoltammetry of ferricyanide in bulk water showed 30% of the peak current observed for naked gold electrodes. 1,2-trans-Cyclohexanediol interrupted ferricyanide penetration into the steroid membrane gaps almost quantitatively; its 1,2-cis diastereomer, on the other hand, had practically no blocking effect. Glucose, galactose, and mannose were also efficient blockers for ion penetration into the hydrophobic gaps. Infrared spectroscopy, quartz balance, radioactivity, impedance, and contact angle measurements on the monolayers and its physisorbed entrapments were used to characterize the membrane system and the unique physisorption process of the highly water-soluble compounds in hydrophobic gaps. A model based on the fitting of polyols with a cyclohexane skeleton and equatorial OH-groups into icelike water clusters and the slowdown of diffusion processes in such rigid and shielded clusters is proposed.

Electrochemical Performance of Self‐Assembled Monolayer Gold Nanoparticle‐Modified Ultramicroelectrode Array Architectures

“…With these in mind, other side effects may be taken into account. Short-chain SAMs appear to be selective to the size and chemical nature of the electroactive species present in solution [49]. Electrostatic repulsion could have an impact on the electron transfer process taking place at SAM-modified electrodes.…”

Rigidity in synkinetic molecular monolayers of functional lipids containing Angstrom Gaps

“…The rational behind these observations is presumably the total immobilization of the surface water within the 7 &wide hydrophobic membrane gaps above the steroids (ref. 19). Only about four water molecules or one 1,2-iruns€yclohexane diol molecule are needed to bridge the gap, which has the width of a steroid.…”

Bicyclic Organo‐Peptides as Selective Carbohydrate Receptors: Design, Solid‐phase Synthesis, and on‐bead Binding Capability

“…A variety of bio-inspired carbohydrate receptors based on porfirins [6], calixarenes [7], steroids [8], aminopyridines [9], cyclodextrins [10], boronic acids [11], or even surfaces [12] have been described. Most of them contain specific recognition motifs, such as hydrogen bond donor or acceptor systems (amides [9b, 9c, 13], (thio)ureas [14], or phosphates [15]).…”

“…After 3 h, resin was washed with DMF (5 Â 6 mL) and DCM (5 Â 6 mL) and reaction was monitored after acidic cleavage of the Rink linker (transformation > 95% from analytical HPLC). HPLC: t R 16.8 min; HR-ES-MS: calcd (M H C 34 H 37 N 4 O 7 S ), 645.2385; found, m/z 645.2410. p-Phenylene-derived linear dodecapeptide (12). To a solution of TPP (210 mg, 20 eq) and I 2 (203 mg, 20 eq) in dry DCM (10 mL) imidazole (54 mg, 40 eq) was added.…”