| Research Abstract |
1. Chemical Sensing Based on Charge Separation
1) New liquid membrane potentiometric sensors for the discrimination of organic analytes based on host-guest recognition of charged groups, hydrogen bonding groups, or steric shapes of nonpolar moieties were developed. A membrane sensor using a cytosine-pendant triamine host showed potentiometric discrimination between guanosine and adenosine nucleotides by ditopic recognition, i.e., complementary base pairing and phosphate-ammonium charge-charge binding interactions at the membrane surface. A calix [6] arene derivative having a well-defined inclusion cavity for organic guests was synthesized and used as a sensory element for the potentiometric discrimination of the steric shapes of nonpolar moieties of dopamine.
2) Permselective ion transport for metal cations at the interface (^-mum depth) of ionophore-based liquid membranes was successfully observed by infrared attenuated total reflection spectrometry (ATR-IR). Furthermore, optical second
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harmonic generation (SHG) was shown to be the first optical technique available for the selective observation of charge separation processes at the surface of liquid membranes. By observing the SHG signals from ionophore-based liquid membranes, the existence of SHG-active, oriented cation complexes at the membrane surface was shown.
2. Chemical Sensing Based on Changes in Membrane Permeability
The control of membrane permeability through intermolecular channels by host-guest complexation was exploited by horizontal tough cyclic voltammetry with condensed monolayrs of long alkyl derivatives of beta-cyclodextrin formed at the air-water interface. Comparing the permeabilities of three kinds of electroactive markers, rigid evidence was obtained that this cyclodextrin derivative functions as an intramolecular channel. The selectivity of permeability inhibition by several organic guest was found to reflect the ability of the quests to block the channel entrance by host-guest complexation.
3. Chemical Sensing Based on Active Transport
Based on highly selective recognition and following efficient transport of D-glucose by Na^+/D-glucose contransporter, a bilayer lipid membrane sensing system for D-glucose was constructed. This active transport sensor enables detection of D-glucose concentrations as low as 10^<-9>M. Less
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