Voltammetric Detection of Lectin Using Sugar Labeled with Electroactive Substance

Abstract

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...

Ferrocene–mannose conjugates as electrochemical molecular sensors for concanavalin A lectin

“…6 By contrast, there are very few cases of biosensors based on carbohydrates labeled with electroactive moieties triggering electrochemical signals upon binding to a protein specific receptor such as a lectin. [7][8][9] There are advantages attributed to electrochemical biosensors such as low cost and high sensitivity with relatively simple instrumentation. Also they are more susceptible to miniaturization and well suited for operating in turbid media.…”

Adsorptive Voltammetry for the Determination of Ochratoxin A Using Enrichment Effect by Cationic Surfactants

“…The affinity constant of OTA‐BSA binding was calculated using the Scatchard plot . The concentration ratio between bound and free OTA was determined from the peak current of free OTA.…”

Voltammetric Evaluation of the Binding between Wheat Germ Agglutinin and Thionine/Glucose-modified Magnetic Microbeads

“…The pattern of the decrease is due to the WGAglucose binding. 20 Then, the peak current became a constant value for over 40 min because of an equilibrium between WGA in a solution and glucose residues on the beads. We decided to set the incubation time at 60 min because the peak current hardly changed from that of 50 min.…”