Insights Into Glucan Polysaccharide Recognition Using Glucooligosaccharide Microarrays With Oxime-Linked Neoglycolipid Probes.
Glucans are polysaccharides of increasing biomedical interest because of their involvement in mechanisms of pathogen recognition, modulation of the immune system and anticancer, and health-promoting activities. Most of these biological activities occur through specific interactions with glucan-recognizing proteins. However, detailed molecular studies of glucan recognition remain a challenge mainly due to the inherent sequence heterogeneity and polydispersity of glucan polysaccharides, and associated difficulties in their purification and sequence characterization. It is thus ideal to have a series of sequence-defined glucooligosaccharides to represent the sequence diversity of glucan polysaccharides and to apply these to gain insight into glucan recognition processes. In this chapter, we describe the the methods for developing of oligosaccharide microarrays derived from a collection of glucans with different linkages based on the neoglycolipid (NGL) microarray system. The microscale oxime-ligation method has provided access in microarrays to over 150 sequence-defined glucooligosaccharides with different chain lengths, linkages, and branching patterns. We focus on the essential steps in the preparation of NGL-based glucooligosaccharide microarrays, which include (1) the depolymerization and purification methods to obtain oligosaccharide fractions of defined chain lengths; (2) a mass spectrometry-based method for linkage and sequence analysis of glucooligosaccharides; (3) improved procedures for preparation of oxime-linked NGLs from glucooligosaccharides for construction of microarrays; and (4) analyses of the recognition of these oligosaccharide sequences by various glucan-recognizing proteins: monoclonal antibodies, other proteins of the immune system such as Dectin-1 and DC-SIGN, and carbohydrate-binding modules of bacterial glycoside hydrolases.