Activity of Fixed Lectin Beads, A Drug Testing Model

Abstract

Lectin derivatized agarose beads are widely used for glycan purification, cell surface analysis, and in the development of anti‐infection and anti‐cancer drugs. These beads have limited shelf life, primarily because lectins, like other proteins, can degrade over time. Here we ask, can fixed lectin beads maintain their binding properties, thereby probably extending their shelf lives? We have already shown that fixed yeast display the same binding properties as live yeast. Concanavalin A (Con A) derivatized agarose beads were fixed with 3.7% formaldehyde in distilled water, washed three times, and their binding to mannose (a Con A binding sugar) rich yeast (Saccharomyces cerevisiae) was compared with unfixed washed beads, in the presence and absence of alpha methyl mannose. In scores of experiments, examining and counting thousands of yeast bound to both bead types, it was found that bead fixation did not inhibit yeast binding, while alpha methyl mannose reduced binding. The results suggest that formaldehyde fixed beads are as active as unfixed beads, offering promise that the shelf life of the beads could be greatly extended. The yeast‐lectin bead system is a useful model for assessing lectin‐glycan interactions, because unlike free glycan‐containing molecules, yeast binding is quickly, precisely and easily assessed by eye, without the need for expensive assay systems. Assays are carried out in 0.2 ml droplets on glass slides, using the flat ends of toothpicks to add beads and yeast and mix samples, plus and minus sugar solutions at varying concentrations. See Zem, et al. (Acta Histochem 108: 311‐317, 2006) for a detailed description of this assay system (Supported by NIH NIGMS SCORE (S0648680), MARC, RISE, the Joseph Drown Foundation and the Sidney Stern Memorial Trust).