Kinetic Analysis of Glycoprotein–Lectin Interactions by Label-Free Internal Reflection Ellipsometry

Introduction Glycoproteomics is undergoing rapid development, largely as a result of advances in technologies for isolating glycoproteins and analyzing glycan structures. However, given the number and diversity of glycans, there is need for new technologies that can more rapidly provide differential carbohydrate-protein structural information on a large scale. We describe a new microarray platform based on a label-free imaging ellipsometry technique, which permits simultaneous detection of multiple glycoprotein-lectin interactions without the need for reporter labels, while still providing high throughput kinetic information at much lower cost. Our results demonstrate the utility of LFIRE[TM] (Label-Free Internal Reflection Ellipsometry) for the rapid kinetic screening of carbohydrate-lectin recognition. The technology was also used to evaluate the benefits of the lectin immobilization format using multi-lectin affinity chromatography (M-LAC) to capture glycoproteins (with enhanced binding strength or avidity) from biological samples. Using a printed panel of lectins, singly or in combination, we examined the binding characteristics of standard glycoproteins. Results and Discussion Using kinetic measurements, it was observed that the binding strength of lectins to carbohydrates is enhanced using a multi-lectin strategy, suggesting that improved selectivity and specificity can lead to increased functional avidity. The data presented confirm that this label-free technology can be used to effectively screen single or combinations of lectins. Furthermore, the combination of LFIRE[TM] and M-LAC may permit more rapid and sensitive identification of novel biomarkers based on carbohydrate changes in glycoproteins, and lead to a better understanding of the connections of glycan function in cellular mechanisms of health and disease. Keywords: Lectins, Glycoproteome, Imaging ellipsometry, Label-free, Glycoproteins, Internal reflection ellipsometry, Multiplexing, Kinetics