Lipid membranes made of lecithin and cholesterol were formed by self-assembly in a small aperture on an agar support. The membranes exhibited an average electric resistance of 135 Gfl and a capacitance of 0.43 µF/cm2. Gramicidin, known to form a channel in uni-lamellar lipid bilayers, reduced the electric resistance to a Mf level, thus showing the membranes to be of a uni-lamellar bilayer type. The membrane stability was investigated against perturbation with electric potentials and against mechanical agitation in the contacted aqueous solution. About 80% of the membrane preparations remained intact after applying electric potentials of between +1500 mV and -1500 mV. A similar percentage of the membranes stayed intact under 100 rpm magnet stirring in a 30 ml vessel. Membranes containing valinomycin responded to K+ ions with changes in both the membrane conductance and the membrane potential.

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A high resolution of doubly charged first row transition (Fe, Cu, Zn, Ni, Co, Mn) and heavy metal (Pb, Cd, Hg) ions was achieved in capillary electrophoresis (CE) with high sensitivity (sub-micromol dm(-3) level), using NN,N'N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) as a pre-capillary derivatizing agent. The non-charged reagent, TPEN, was applied to capillary zone electrophoresis (CZE) for the first time. Since complete spatial separation between the complexes and the ligand was carried out in a carrier buffer, which was free of TPEN, kinetic inertness of metal complexes was necessary for the detection in this pre-capillary method. All the nine listed metal complexes were detected: Ca(2+), Mg(2+), Al(3+), Fe(3+), and Co(3+) complexes were undetectable. This, interestingly, suggests that those nine cations form kinetically inert tpen complexes without strong charge-charge interactions between the metal ion and the ligand. It is expected that the hard-soft-acid-base (HSAB) principle governed the kinetics selectivity. With respect to the electrophoretic behavior, the addition of chloride ion and methanol to the carrier significantly improved the resolution. This is due to the formation of ternary complexes or ion aggregates and the solvation effect, respectively. These effects provided a satisfactory baseline resolution among the nine metal ions. An application to biological samples was demonstrated. Some metal ions in human serum and urine were successfully detected in a simple process without the need for deproteinization using a non-coated fused-silica capillary because of the differenciation in the direction of migration between organic matter and complexes.

Lectin, is a protein existing in plants, bacteria and animals. It is known that it contributes to cell control, the aggregation of cell and the formation of organization. Lectin has a property that combines with a sugar residue having a specific structure. The lectin-sugar interaction is related to the membrane receptors of neurotransmitters, hormones and growth factors. [1][2][3] Lectin is also important in medical and clinical fields. 4,5 Therefore, a number of studies concerning the binding between lectin and sugar have been reported. For example, the sugar-binding sites of lectin were determined by affinity chromatography. 6 The affinity constant of lectin-sugar binding was measured by capillary electrophoresis. 7Investigations on the domain of carbohydrate for recognition and the structure of lectin by NMR were also attempted. 8,9 On the other hand, more sensitive and selective methods are needed to understand the function of the lectin in living bodies and to explain the interaction between lectin and sugar in detail. At present, solid-phase assay with an enzyme, 10 method using the avidin-biotin interaction, 11 immunofluorometry 12 and electrophoresis 13 are shown to be useful probes. Although these procedures are sufficient in sensitivity, the separation step contained in them is complicated.Accordingly, the development of a procedure without any separation step is desired. We have already reported a useful electrochemical method used to evaluate the avidin-biotin interaction. It is an advantage of this method that the separation of a free biotin from a bound one is not necessary. 14-16 This procedure will be useful for a rapid evaluation of the concentration of the lectinsugar binding. Based on this background, study that evaluated the lectin-sugar binding by an electrochemical method was first developed by us. In a previous study, a soybean agglutinin (SBA)-galactosamine interaction was reported. 17 The procedure was as follows.Galactosamine and an electroactive daunomycin were combined with a cross-linking reagent (ethylene glyco bis sulfosuccinimidylsuccinate). A sensitive voltammetric measurement was achieved owing to the strong adsorption of daunomycin and a spacer on the electrode. When a part of daunomycin is taken to the binding sites on the basis of the SBA-sugar interaction, the electrode response of daunomycin decreases. Thus, the interaction was evaluated from the change of the electrode response. Generally, it is expected that the peak of the labeled sugar disappears with a sufficient amount of lectin. However, the peak current of daunomycin did not become zero, even if a sufficient amount of lectin that combines to all of the labeled sugar existed. The reason may be that the electroactive part is not perfectly covered with binding sites of the lectin. Consequently, the length of the alkyl chain between sugar and the electroactive part (spacer) for lectin-sugar binding should be investigated.In this study, labeled sugar in which the length of the spacer was shorter was prepared, compared to...