Biotinyl-l-3-(2-naphthyl)-alanine hydrazide derivatives of N-glycans: versatile solid-phase probes for carbohydrate-recognition studies

Biotinyl-oligosaccharides are a relatively new generation of saccharideprobes that enable immobilization of desired oligosaccharides onstreptavidin matrices for studies of carbohydrate-protein interactions.Here we describe the facile preparation of biotinyl-l-3-(2-naphthyl)-alanine hydrazide (BNAH) derivatives of oligosaccharides, containing astrong UV absorbing and fluorescent group, in which the ring of thereducing-end monosaccharide is nonreduced. We evaluate reactivities ofimmobilized BNAH- N -glycans with plant lectins that recognize aspects ofthe oligosaccharide core or outer-arms. We make some comparisons with2-amino-6-amidobiotinyl-pyridine (BAP) derivatives obtained by reductiveamination, and 6-(biotinyl)-aminocaproyl-hydrazide (BACH) derivatives whichhave a longer spacer-arm. N -Glycan-BNAH and-BAP derivatives have, overall,comparable reactivities with lectins which recognize N -glycan outer-armsor the trimannosyl core, but only BNAH and BACH derivatives are bound bylectins which recognize the non- reduced core. Moreover, with Pisum sativumagglutinin (PSA) which additionally requires the fucosyl- N-glycan-asparaginyl core for high affinity binding, the immobilized BNAHderivative (which is an alanine hydrazide beta-glycoside) can substitutefor the natural beta- glycosylasparaginyl core, whereas the BACH derivative(aminocaproyl- hydrazide-beta-glycoside) is less effective. BNAH is aderivatization reagent of choice, therefore, for solid phasecarbohydrate-binding experiments with immobilized N -glycans.