Chemoenzymatic synthesis and fluorescent visualization of cell-surface selectin-bound sialyl Lewis x derivatives

Sialyl Lewis x (sLe(x)) derivatives conjugated to readily visualized molecu lar labels are useful chemical probes to study selectin- carbohydrate inter actions. Localization of the selectins on the surface of leukocytes and act ivated endothelial cells can be detected through fluorescence of bound sele ctin ligands. Herein we present a short chemoenzymatic synthesis of a fluor escently labeled bivalent sLe(x) conjugate, The use of an amino-substituted monovalent sLex to obtain fluorescent- and biotin-labeled sLe(x) derivativ es is also described. The cell-staining utility of the fluorescent sLe(x) c onjugates is demonstrated for a HUVEC cell line expressing E-selectin and f or CHO-K1 cells expressing either L- or E-selectin.