Analytical Sciences

Voltammetric Detection of Lectin Using Sugar Labeled with Electroactive Substance

Kazuharu SUGAWARA,*  Hideki KURAMITZ,** Takashi KANEKO,*** Suwaru HOSHI,*** Kunihiko AKATSUKA,*** and Shunitz TANAKA**

*Faculty of Education, Gunma University, Maebashi, Gunma 371-8510, Japan
**Division of Material Science, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
***Faculty of Engineering, Kitami Institute of Technology, Kitami, Hokkaido 090-8507, Japan

The voltammetric detection of soybean agglutinin (SBA) was investigated on the basis of an interaction between the lectin and a sugar. Because galactose and lactose combined with SBA, the sugars were labeled by a Schiff base with an electroactive daunomycin. After the labeled sugar and SBA were mixed, measurements were carried out by voltammetry. When SBA-sugar binding occurs, a part of daunomycin of the labeled sugar is taken to the binding sites. As a result, SBA is detected by a change in the peak current of daunomycin, and the SBA-sugar interaction is evaluated. The length of the alkyl chain between daunomycin and the sugar was also considered. The electrode response to the concentration of SBA was linear over the range of 0.04 - 0.8 ug ml^-1. The merits of this procedure are the convenient preparation of labeled sugar and a rapid measurement without separation. On the other hand, the detection of sugar at the 10^-9 mol dm^-3 level was achieved by a competitive reaction to limited binding sites of the lectin between the sugar and the labeled sugar.

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