Voltammetric detection of lectin using sugar labeled with electroactive substance

The voltammetric detection of soybean agglutinin (SBA) was investigated on the basis of an interaction between the lectin and a sugar. Because galacto se and lactose combined with SEA, the sugars were labeled by a Schiff base with an electroactive daunomycin. After the labeled sugar and SEA were mixe d, measurements were carried out by voltammetry. When SEA-sugar binding occ urs, a part of daunomycin of the labeled sugar is taken to the binding site s. As a result, SEA is detected by a change in the peak current of daunomyc in, and the SEA-sugar interaction is evaluated. The length of the alkyl cha in between daunomycin and the sugar was also considered. The electrode resp onse to the concentration of SEA was linear over the range of 0.04- 0.8 mug ml(-1). The merits of this procedure are the convenient preparation of lab eled sugar and a rapid measurement without separation. On the other hand, t he detection of sugar at the 10(-9) mol dm(-3) level was achieved by a comp etitive reaction to limited binding sites of the lectin between the sugar a nd the labeled sugar.