Tomato lectin is a very stable single subunit glycoprotein containing about 50 percent arabinose and galactose and may form multimeric aggregates in solution. Tomato lectin, although sharing some specificities with potato lectin, Datura lectin, and wheat germ agglutinin, has been reported to be dissimilar in many respects. LEL binds well to glycophorin and Tamm-Horsfall glycoprotein and has been used effectively to label vascular endothelium in rodents.
Agarose bound* tomato lectin is prepared using our affinity-purified lectins. Heat stable, cross-linked 4% agarose beads with a molecular weight exclusion limit of about 2x107 daltons are used as the solid-phase matrix to which the lectins are covalently coupled. The attachment of the lectins to the beads is carefully controlled to preserve lectin activity and minimize conformational changes of the bound lectins that might result in nonspecific ionic or hydrophobic interactions. The technique we have developed to couple lectins to agarose beads inserts a hydrophilic spacer arm between the lectin and the matrix.
This coupling method provides several advantages over the traditional cyanogen bromide procedure:
Maximum carbohydrate binding activity of the coupled lectins is retained
Linkage is stable over a range of pH values
Conjugated proteins are not leached off the beads by Tris or other routinely used buffers
No residual charges are present after conjugation. This minimizes non-specific binding to the matrix.
Our agarose bound lectins are supplied at a constant concentration of lectin per ml of settled beads. The concentration for each lectin is selected to achieve the highest glycoconjugate binding capacity per mg of lectin present in the beads. Each lot is tested for its binding capacity using glycoproteins known to bind the lectin. This provides a guideline for the user and assures the quality of our agarose bound lectins.